HP 5065A Rubidium Standard Repair Log - Page 1
Forum section: electronics / general

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 01:34:44 am
content: I recently got a rare HP 5065A Rubidium frequency (secondary) standard off Ebay (https://www.eevblog.com/forum/buysellwanted/fs-(uk)-hp-5065a-rb-frequency-standard-other-calibrators/). This is one of the old time goodies.It was a "For Parts" sale and the seller didn't give much info, but it was a rare opportunity to get one of these over in Europe and shipping from the States is a killer due to their weight. So it took my chances, expecting the worst and hoping for the best. The 5065A arrived this week and a first glance revealed that (one of) the previous owners was "Devonport Management Limited". Port? Do I hear sea port? Salt water? Yes, you guessed it, mild corrosion everywhere, but lets do an inventory first.This is a rather recent 1989 model with all options (that is option 001 and 002). Option 001 is a clock module, which gives us a, well...uhm, clock, a 1 pps output and a sync input. This is a must have for anyone who can't stand it, when the integrated clock of your favourite data logger goes out of sync. Love it! I'll never miss a second for the rest of my life.Option 002 is a NiCd backup battery which gives you 10 minutes of battery life for a whooping 16 h of charging. We will get to that later.Being a more recent model it also features the better 10811-60109 OCXO. Very nice indeed.I don't have a power cord yet, but that is something Mouser can fix. Meanwhile I opened it up and took a few pictures. Unfortunately half of them are still on the mobile phone of my colleagues, so I will post them later. The first thing I was greeted with, was a bag with “loose nuts and screws” written on it – bad sign. The rubidium cell was disconnected and the wires hanging loose. The battery was corroded and had spilled its guts – yuk. But otherwise at least everything seemed to be there. Nothing missing at first glance. The first picture shows the the inner assembly, from which I have removed the battery the A6 board and the rubidium cell. You can see some of the rust I was talking about on the oscillator housing in the right bottom corner.I checked the boards and obviously someone already had a shot a repairing them. Man, I just love it when people leave the flux on the boards...Some of the boards have new caps on them, but no cleanup was done in the areas which had signs of capacitor leakage. I will post the pictures of the boards as soon as I get my hands on them. All the boards will require new caps and some thorough cleaning to get rid of the copper oxide.What do you guys think is best? Citric acid or vinegar? Then some sodium bicarbonate (baking soda) to neutralize, distilled water and finally IPA. That would be my strategy and everything that is left will meet my friend, the fibreglass pen.

author: Theboel
author_rank: Frequent Contributor
timestamp: March 16, 2019, 01:56:25 am
content: Good Luck for repair Your 5065,if You continue to report the progress I believe some Gentlemen will very helpful.btw one of the very kind and talented gentlemen already looked at Your threadno no no its not me

author: edpalmer42
author_rank: Super Contributor
timestamp: March 16, 2019, 01:59:04 am
content: Mine also had the battery option and it looked about as bad as yours. I decided not to replace the batteries, but I did keep the plastic battery holder - just in case I change my mind later.For the power cord, don't bother with Mouser yet. That military connector is pricey. Just go into your junk box and find three female sockets that are close to the right size. Solder them onto a cord, pinch them down so they're a snug fit, and heatshrink them for safety. If you really want to, use a cable clamp to hold the cable in place so there's no strain on the connectors. Once you've got the unit working, you can decide if you want to get the proper connector.Regarding dead capacitors, take a look at this picture:This isn't my unit, but mine was about this bad. I almost didn't realize that there's supposed to be a trace under the third capacitor that passes under the two resistors and carries on to the right. On my unit, that trace was completely gone. Watch out for that. I just used vinegar and then water to clean up the boards. By the way, the picture is from this page:http://www.niceties.com/atomic.html.Ed

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 02:14:52 am
content: In the meantime I had a look at the lamp assembly. Oh deary me, I see mishandled PoziDriv screws. Just a reminder for everyone repairing HP gear. The usually use PoziDriv for their gear. So check your screwdrivers before digging in! The PoziDriv screws have additional radial indentations at 45° from the main cross. Do not use a Phillips screwdriver on them, ever! (Unless you are disarming a bomb and running out of time, but even then...show some respect for your gear). I can highly recommend Wera screwdrivers with the laser tip (not affiliated in any way). They have incredible amounts of grip even with damaged screw heads.Back to topic. This is not a good sign, because Mr. NoCleanFlux was probably meddling inside. So I did a sneak peak as well. The lamp seems fine (picture 3), but what is that on the bottom side of the pcb? Can you spot it? Black marks on the mounting spacers. Uh Oh. Reminds me of IT crowd.And of course more havok from Mr. NoCleanFlux. So yep, he was here as well. Probably trying to clean up the burn marks. See picture 4 to see what it looks like underneath. Again look closely. Hint: the black capacitor. Crack in the middle. Next to it char marks in black on another component. Ok, I will have to rip that apart as soon as I identified the damaged parts. The red "blob" in the background is another capacitor. Broken as well...So we had quite a hot party going on here. But the good news is, that the lamp looks fine. Phew. Lets see what the vapour cell looks like. I am in luck. No broken glass. Looking good.

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 02:33:30 am
content: Yep my boards look mostly like that, with A6 in a little worse shape, which is why I removed it for now. I will check all caps and probably replace them just for good measure.I haven't decided on the NiCd batteries yet. But I guess I am ever going to retrofit batteries, it will be a lithium ion pack. The charger board A6 is slightly charred anyway. From the schematics it looks like a drop in replacement board with a lithium ion charger should be doable.

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 12:49:52 pm
content: I finally got the pictures, my colleague took. So here they are:First the device as received:Then a leaky battery:

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 12:52:55 pm
content: The well cooked A2 battery charger board:Yeah, sure thing. Put 85 °C, 2kh, replacement caps on a board that shows burn marks.Backside:

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 01:10:56 pm
content: The A15 power supply board:This is the newer version 6100, which was a replacement for the original 6023. Again lots of flux residue. And I will have to replace those blue 85°C, 2kh caps again.Backside:

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 01:18:20 pm
content: The A14 logic board:Pretty decent shape. Some transistor caps are little dull, but overall very nice.Backside:

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 01:34:03 pm
content: The A9 Integrator board:Again this is an upgrade to the older 5060-6015 board. Again flux residue on the OPA111 (https://www.ti.com/lit/ds/symlink/opa111.pdf). Nice opamp, btw. You can still get them. I keep my fingers crossed, that this one is ok...$50 a pop for a new one...I love that handle they put on the board. This is a ingenious, because the boards are rather hard to pull out.Backside:

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 01:51:29 pm
content: The A4 100 kHz frequency divider:This is one of the boards in worse shape. We are getting closer to the leaky battery. The cap needs to be replaced, as it is leaking as well. Does anybody know the model of the the transformer T2? It has the HP part number 05061-8008. I don't like the rust on that one. I will desolder it and have a look at the bottom side.Backside:

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 02:09:53 pm
content: The A8 phase detector:This board will require some vinegar treatment as well. Unfortunately one of the caps used in the oscillator part, C3, is a little corroded as well. Its a 25.2 nF, 1%, PS, 50 V capacitor. I will see how bad it is, because this one might be hard to source.Backside:Rusty PS capacitor:

author: maat
author_rank: Regular Contributor
timestamp: March 16, 2019, 02:27:28 pm
content: Finally the A6 1 MHz frequency divider board:I don't like what I see. I hope the transformers are allright and we will see how the trimmable cap survives the washing. Thats it for now. I did not yet pull out all boards. Got to get back to the kids nowBackside:

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 16, 2019, 02:46:08 pm
content: Doesn't look that bad.Good luck, furthermore.Frank

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 16, 2019, 04:07:10 pm
content: Maat,Thanks for the PIX! The only thing I see preventing an initial power up is the missing Db9 chassis connector for the optical unit. You need to very sure you wire it correctly! As Ed mentioned Make up a power cord with 3 female pins that fit onto the power pins. Heat shrink them. That way you can troubleshoot without having to wait for a connector.If you are going to work on the lamp assy. replace the 1.33K film resistor as they are a failure point. I use 1.3K 2% 1 or 2 Watt metal oxide resistors. Once happy with the repairs you can test without installing into the optical unit by connecting +20V on the bench and after a minute or so the lamp should light. About 150mA lamp out and drops to about 125mA when the lamp comes on.Your shot looking into the optical unit shows the Rubidium filter cell. The other end houses the Rubidium reference cell but it's not visible as it's inside the microwave cavity. DONT remove as retuning the cavity is a chore!Good Luck!Corby

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 16, 2019, 05:56:22 pm
content: Maat,In order you presented.A2 not really cooked, that is a rather clean example. ( As I normally remove the battery option that board goes also.)A15 has some damage from the 100uF caps but otherwise OKA14 OKA9 looks fine the op amp should be OK (during the 5065A alignment if not using the manual/changes that include this board set/check the loop gain on the CW 50 units only!)A4 I see the pesky 100uF! The transformer should be OKA8 I'd pull the PS cap, clean its leads, re-tin and put it back in. I can provide a replacement if needs be.A6 100uF cap again, I've never seen a TX fail, DONT adjust the cap unless absolutely required and if so let me give advice first.When you get to the A11 replace the two 22uf electros.Cheers,Corby

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 21, 2019, 03:21:24 pm
content: Maat,While you have the lamp assy removed check and see what condition the reflector is in.They can get corroded and lose reflectivity. You can look through the Holes in the front disc and also from an angle through the rear hole with the reflector removed.I have found that "Mothers" Aluminum polish and some elbow grease will polish them up nicely!After removing the reflector from the assy. and removing the 3 screws holding the perforated disc you will most likely find the disc stuck tight. I put the reflector assy. in a vise at an angle and apply pressure till it pops free. Then push the clear glass disc out of its recess to get at the reflector surface.Cheers,Corby

author: maat
author_rank: Regular Contributor
timestamp: March 21, 2019, 11:45:46 pm
content: Thanks for the hint Corby, I hope that tomorrow I can spare I bit of time and work on the 5065A in the evening

author: maat
author_rank: Regular Contributor
timestamp: March 23, 2019, 12:20:54 am
content: So here it is: Part IIToday I took apart at the the (upper) lamp assembly to get a look at the rf generator and that cracked mylar cap (red circle on the left side). I carefully desoldered the wire connecting the the power supply and the board (red circle on the right) and removed the screw pressing the heat sink of Q1 onto the aluminum base plate.Since there is no picture of the RVFR board in the manual I decided to take one. I am not sure if C3 is small green cap. I forgot to check with a multimeter. Does anbody know, what the two white tubes are (e.g. between L2 and R2)?

author: DC1MC
author_rank: Super Contributor
timestamp: March 23, 2019, 12:31:51 am
content: The little tubesare small ceramic capacitors in 10s up to 2-300pf range.Cheers,DC1MC

author: maat
author_rank: Regular Contributor
timestamp: March 23, 2019, 12:40:46 am
content: Capacitor massacreUpon inspection of C2 it turned out that, those mica caps are definitely some sturdy bunch. I desoldered it to have a look at the crack and it turned out, that part of the back side was missing as well. Poor thing, but still hanging in there and within specI also pulled C1, because it had some hairline fractures and I do not want it to short out and burn down my lamp assembly. The weird thing was, that C2 was 130 pF instead of the 110p given in the datasheet. Did they tune each circuit by hand? Anyway, since the lamp worked before I pulled the caps. I will replace them with the same value.

author: maat
author_rank: Regular Contributor
timestamp: March 23, 2019, 01:09:45 am
content: Cleaning up the batteryNext I started cleaning up the mess the battery caused in its final hours. I removed all the boards to prep them for cleaning and also removed the aluminum housing that contained the battery and the one that contained the boards, Fortunately those two assemblies are the ones most affected and the Multiplier A3 housing will probably get away with some exterior isoprop cleaning.Starting to look empty:This is what those parts looked like. All tarnished by the acid.I gave them a good scrub in soapy water, which removed some of the larger particles. But since the tarnished aluminum was there to stay. I got out the the sandpaper, grit size 600 and I removed just the upper layer of oxide. Using water during sanding helps. Do make sure that you are sanding only in the direction of the original pattern. Except for some places, where the acid has really eaten into the material the battery compartment now looks like new.I will use the angle grinder and a stainless steel wire wheel to remove the oxide layer in the rest of the case once I have decided what to do with the big electrolytics used to filter the mains. They got spilled with acid as well and show some decent corrosion on their base plate. I will probably remove one of those next to have a look underneath.

author: FriedLogic
author_rank: Regular Contributor
timestamp: March 23, 2019, 08:40:31 am
content: I normally used a wire brush with all brass bristles on aluminium, although it occasionally needed a steel brush or point for stubborn or deep corrosion. The stuff that gets brushed off and even the wires from the brush can sometimes be a problem if they go where they shouldn't.A lot of old component leads get some level of corrosion on them for various reasons, but the extra handling/cleaning/chemicals/soldering/etc. to remove it can easily result in 'collateral damage'. It can be a bit of a judgement call what to do.Brushes like a toothbrush and small artists type brushes can be very good at cleaning around components even with basic cleaners like IPA, or water with a small amount of washing up liquid in it. A lot of electrolyte gunge dissolves better in water than alcohol.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 23, 2019, 04:10:30 pm
content: Maat,The schematic you are using for the lamp assy is an old one.The 130pf cap is correct. No tuning is done.Tubular ceramics are 3.9 and 11 Pf and I've never seen one go bad.The tiny cap is a .001uf monolithic radial.CR1 is a multi-pellet diode and can't be checked with an Ohmmeter. (Never seen a bad one!)Make sure when you remount it that you hold the transistor heat sink while tightening so as not to twist the transistor leads!Also once you reassemble (you should have had two big nuts and a fiber insulator on the central lamp post) position the inner nut so that when you tighten the outer nut onto the fiber washer it clamps the outer magnetic shield between them as the outer shield forms a heat sink for t e lamp assy.!How does the reflector look?Cheers,Corby

author: maat
author_rank: Regular Contributor
timestamp: March 24, 2019, 03:15:15 am
content: @FriendLogic: Thanks for the input. It's always good to get some second opinion on stuff. I am not too keen on using brass with aluminium, though. It might be a non-issue, but I don't want tiny pieces of brass to be the cause of galvanic corrosion. I know stainless is not perfect either, but better non the less. I also happen to have a stainless steel wire wheel laying around. So I will give that a whirl (pun intended). Component leads I usually clean up with a fibreglass pen and some IPA.@Corby: Thank you very much for reminding my about the refractor. I took that apart as well (or at least I tried). I used a screwdriver with some tape on the tip and bit of gentle force so separate the refractor from the protector and it came off nicely.But then the joy vanished. HP used silicone to glue the glass in place! I *could* try soaking it in WD-40, make a Peek stencil and use a puller to force it out...But I would say that refractor looks good enough.Just some ramblings of a laser physicist: When/if I ever get to replace that window with an optical filter I will revisit that issue. But before I do that I got to talk to the other physics group across the hallway, because they have one of those fancy Anritsu OSAs. That might give a clue as to what to remove from the spectrum. But then again I might just as well rip out the lamp. Install a fibre pigtail, grab a 780 nm ECDL from the bench and drive that D2 line properly...I mean it is all there. The whole physics package. That line is big as barn…Driving from F=2 to F’=2 is fairly simple. Then repumping the decaying atoms from the F=1 back to F=2 would result in the desired dip in the laser intensity. Alright, enough dreaming!

author: maat
author_rank: Regular Contributor
timestamp: March 24, 2019, 03:59:31 am
content: Quote from: 5065AGuru on March 23, 2019, 04:10:30 pmThanks a lot for the info. I will just replace the two caps then. The rest seemed fine.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 24, 2019, 04:07:01 pm
content: Maat,I usually use my smallest finger and just push HARD on the glass from the rear and it pops out.Take a look here for details of an optical filter mod.http://leapsecond.com/corby/Corby-Super-5065A-Project.pdfAlso the yield when trying the mod is small as everything else has to be in better that spec. condition.Just remember you will need a Hydrogen MASER to test it!That goes for trying the Laser excitation also.A friend has been trying the laser excitation for a few years now and its just not feasible yet.Why replace a simple lamp that lasts 30 years with a costly Laser system whose reliability can't compete?If you try it details would be most welcome!Cheers,Corby

author: maat
author_rank: Regular Contributor
timestamp: March 24, 2019, 04:48:28 pm
content: Quote from: 5065AGuru on March 24, 2019, 04:07:01 pmSo yours are glued in as well? I will give it a shot next time I take the lamp appart when installing the caps.Concerning the lifetime of of the laser diodes is indeed an issue. In my university group, we are mostly using Sharp GH0781JA2C and with optical feedback these last about 2-3 years non-stop before degrading. This number will be higher with less output power, which is a seasonable asumption, because I only need to drive the saturated absorption spectroscopy and less power is better anyway. Cost is another factor. Laser driver, TEC controller, external resonator, the laser filter, Lock-In Amplifier and fibres including splitters will put you down by about 5-10 k$ depending on how much you can do yourself. But this is a nice 'benchtop' experiment one can run in the basement with reasonable cost of ownership while still being close to modern day physics lab experiments.

author: edpalmer42
author_rank: Super Contributor
timestamp: March 24, 2019, 05:35:10 pm
content: Quote from: 5065AGuru on March 24, 2019, 04:07:01 pmCorby, do you mean it's not feasible for a retrofit? The Microsemi Miniature Atomic Clock uses a VCSEL (Vertical Cavity Surface Emitting Laser) instead of a Rb lamp. The light isn't visible to the eye, but a camera can see it. I have one that is, unfortunately, dead, but it's fascinating to watch it try to find a combination of parameters that will get a lock. It spends something like 3 hours trying before it gives up!SA.3Xm User Guide:https://www.microsemi.com/document-portal/doc_download/135918-sa-3xm-miniature-atomic-clock-mac-user-guideEd

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 24, 2019, 07:05:08 pm
content: Ed, I know about the Microsemi device.My point about feasibility, not so much that it could not be done albeit at much expense and fiddling. (Which don't get me wrong, can be fun) However I try to balance modifications to those that improve or at least maintain the existing 5065A performance with a lifetime that is long enough to warrant the effort. So far examples I have seen don't come close. Remember an excellent performing 5065A will have an Allan Deviation approaching or exceeding 1X10-13th at a 100 Sec Tau. The Microsemi units depending on which spec you purchase are 1X10-11th or 8X10-12th at 100 Sec. Of course no modern (commercial) Rubidium comes close to matching a 5065A performance! The drive to smaller, cheaper, low power, directly affected the short term stabilities achieved by modern Rubidium units.Cheers,Corby

author: edpalmer42
author_rank: Super Contributor
timestamp: March 24, 2019, 08:17:58 pm
content: Quote from: 5065AGuru on March 24, 2019, 07:05:08 pmI was sure that you were familiar with the Microsemi device, I just didn't quite understand your comment.Ed

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 24, 2019, 08:51:39 pm
content: Maat,It's RTV not cement holding in the glass. It's soft and just to keep it from rattling around!The bits of original RTV are usually fine when reinstalling. I've never had to use new RTVCheers,Corby

author: maat
author_rank: Regular Contributor
timestamp: March 29, 2019, 11:31:25 pm
content: Today was bathing time!From left to right. Distilled water with a dash of Simple Green, Acetic acid mixed with distilled water and finally pure water. There is also a forth bowl with IPA not shown in the picture. I usually start by scrubbing off any ooze, corrosion and minerals that are on the board. When I have a bare copper surface, that is only tarnished from oxidation, I put it in the vinegar bath until the copper is shiny again (a few minutes). Then I wash it in pure water to remove the acid. You may add sodium bicarbonate, but watch out if you use baking soda. Sometimes manufacturers add other stuff to the sodium bicarbonate as well. Check the package first. Then drown it in IPA. Depending on the time it was in the water I usually leave it in there for a while to remove all the moisture. Finally I use compressed air to blow off the IPA. If there are still some stains, reapply IPA, and then immediately wash with distilled water, then soak in IPA again. Usually these are flux residues that get dissolved in the IPA, but rinsing with water while the IPA is still liquid usually takes care of the stuff.Once I am done with cleaning and the copper looks good again, I apply a layer of solder to protect the copper for all eternityThis is the A15 Board as an example:I removed the capacitors and the diode in the middle, which looks like this:after some scrubbing, the green copper sulfite (from a leaking tantalum capacitor probably replaced by the previous owner) the corrosion is gone, but we are left with a layer of oxide. I is impossible to solder to this oxide layer, so we need to remove it first.Unfortunately I did not take a photo after the acid bath, but only after I was completely done.I overdid the solder patch a little in this case. This pad was a GND pad, but the plated holes had no contact, because the copper was already gone around those. So I just poured it with solder then washed it again, leaving a shiny blob of solderThe three tantalum caps looked new (old stock?) to me and their capacitance and ESR (a little more than 1 Ω @ 100 Hz) seemed fine so I left them in for the moment, but I will replace them as soon as Mouser ships my replacement caps (long, long time...)I also paid that corroded polystere capacitor a visit with the fibreglass brush. Worked like a treat:Then retinned the lead:So far so good. I cleaned most of the boards shown in the previous post and I also cleared out the interior of the case so see how far the battery acid had spread:I think I will try the vinegar again and then some polish to touch it up. We will see how it goes. While life was looking good a new horror crept up on me; the A3 Multiplier Assembly:I can hear a rattling inside and there is stuff rolling aroundI did not yet open it, because the screws have been massively abused and I was running out of time anyway. I guess this could be the board where the previous repair attempt met a gruesome end.To be continued...

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 30, 2019, 04:05:46 pm
content: Maat,The rattling in the A3 is probably a corroded 100uf tantalum that has come loose.The A3 has lots of screws and they can be difficult to get loose.Once you have gotten inside and repaired it you need to make sure the two ceramic trim caps that are next to each other (the output matching stage) are not "stuck". One problem people introduce is to try to turn these and break loose the rotor connection. If they don't rotate with moderate force then you need to apply pressure to the rotor section sideways to break them free. I usually do this while the cover is on by inserting a stiff plastic rod through the tuning hole and pry sideways against the rotor using the leverage against the tuning hole until its free. There are more of those caps and you could break them free while you are at it but the critical ones are the two I mentioned.Also when you power it up the first time quickly check the plus/minus 20V volts. I also put a scope on the two chassis mounted choke connections. One should be flat DC the other an unfiltered full wave rectified signal.The only reason I check this is that I once had a unit with a shorted choke. Never seen that since but I still check.Cheer,Corby

author: maat
author_rank: Regular Contributor
timestamp: April 14, 2019, 02:25:02 am
content: It is time for another update. I took the whole units apart and finally cleaned everything. The upside is, that I am now corrosion free. The aluminium still has some etch marks to show for, but I consider that artThe downside is, that some of the labels printed onto the aluminium are now gone. Oh well, there is always something...In the meantime my power connector arrived. Or so I thought. I had ordered an MS3106A18-22S connector and at that time I did not bother reading through the full 70 pages of the datasheet of that connector family. As it turned out there are multiple versions of the that connector. Hidden somewhere in the far back of the datasheet there is a section "insert alternate positioning". In total there are five different versions of the connector, differing in the position of the pin insert. Well..., trip to the milling machine and now I am the proud owner of a dual connectorJust in case someone needs that connector. The correct part number istMS3106A18-22SW(the W at the end denotes a 70° rotation of the pin insert). Digikey link:https://www.digikey.com/product-detail/en/amphenol-industrial-operations/MS3106A18-22SW/AMS3106A18-22SW-ND/2128451So finally, I powered up the unit without any of the circuit boards installed to check the transformer output. I do have ~28 Vrms (around 40 V after the rectifier) between between pins 5 and 6. Looked a little high as the manual said 24-32 V, but then again that is unloaded, so it might be OK. Nothing blowing up so far, I decided to install A15 (power supply) and A2 (battery charger). The battery charger is required, because it contains the OR-ing circuit to either connect the battery, the DC supply or mains. Units without option 002 or 003 will contain the A18 jumper board to do the job.Powering up again things looked nice as well.I have got nice and stable 20.01 V on the 20 V rail, but still those 40 V on the input side to the A15 board, again that is mostly unloaded.. But seconds after I took that picture there was a bright flash and the circuit breaker in the lab triggered. Bummer....Checking the source, I noticed an awful smell and lots of ash around the power input. Nothing on the circuit boards. Phew. Taking a closer look, I found the charred remains of what looked like a capacitor. Guess what, acute RIFAlitis. There are two capacitors C5A and C5B connected from both live and neutral to earth. These are Y2 caps. Supposed to failopen!Anyway, I pulled both capacitors and the surviving one was already showing cracks. The dead one literally exploded.For now I am living without them, because I need to order new ones. While I was at it, I also decided to put shrinking tube on all accessible solder joints that carry mains voltage. HP..., hello?!So a word of caution to everyone buying a used 5065A, you might want to check the caps or RIFAlitis.Next up to install is the physics package to see if the heaters are working, but I am still waiting for those mica caps. It will probably be another week before they arrive.

author: Oldtestgear
author_rank: Regular Contributor
timestamp: April 14, 2019, 11:51:36 am
content: "Devonport Management Limited". Port? Do I hear sea port? Salt water?Devonport management Ltd. took over the old Plymouth Dockyard when the MOD started sub contracting core activities to private companies. So definitely sea air & salt water,Phil

author: trobbins
author_rank: Frequent Contributor
timestamp: October 01, 2022, 03:29:16 am
content: Just to extend this log, although for another 5065A, I have been able to reinstate a 00105-6013 crystal oven assembly after it had multiple part faults including shorting heaters to ground and 'cooked' internal insulation foam. The internal can needed to be exhumed from its solid foam coffin and the heater winding and insulation inspected - the AC preheat heater was not needed (and was a problem for any mains earth leakage cb) and carbonised deposits were carefully scraped away to achieve a reasonably ok insulation resistance from the dc heater to can - and the can then re-centred in the assembly using neoprene foam strips. Failed parts were the two voltage doubler diodes for temperature feedback, and the following npn, and the heater temp adjust trimpot at the other end pcb, and the entire ribbon cable was charred and replaced. The coarse freq adjust pole had also suffered and was broken deep inside the can, with no ability for adjustment, so the heater temperature trimpot was used to trim to 5MHz to within 10ppb with the fine freq adjust in centred position - the heater trimpot adjustment gave about +/- 1.2Hz span, so although using that control may affect some performance specs, it was the only way forward for this assembly (given I didn't want to crack open the can for a deep-dive).Now I'm just about to start excavating the lamp oven heater from within the RVFR can, as the filament has gone open and is shorting to the heater mount ground. At least the first-aid docs indicate that the lamp heater can be repaired (although no photos available), so I will take some photos along this voyage of discovery.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 04, 2022, 12:10:57 am
content: T Robbins, Have you looked over this post about the lamp oven repair? If you have and plan to follow it I have a couple new bits of info. if you want.https://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details!/Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 04, 2022, 03:25:47 am
content: Hi Corby, thanks for chiming in - much appreciated. I tried to access your lamp oven repair link a few days ago, but that link is broken afaik (?).I have been in touch with syau (Stanley) - his thread photos show an early version of insulation and construction of the lamp heater region. My partly deconstructed region is shown below - the heater filament had fused, and the foam insulation had baked next to the aluminium cylinder but was able to be gouged out with care. Although part of the magnetic field coil has been exposed, I aim to constrain that and not uncover any more. My concern is how much of the original heater I can uncover without disrupting or stressing the DB9 cable's connection to the lamp heater thermistor, and to the cell oven wiring. I don't really want to disturb that wiring if I don't have to, and so doubt that removing the aluminium cylinder (as Stanley did) is a practical path to take. I would appreciate any advice you can offer.I asked Stanley about his spare Pelican wire (as you also did), and also am on the lookout for a local alternative.Ciao, Tim

author: bingo600
author_rank: Super Contributor
timestamp: October 04, 2022, 07:58:22 pm
content: Quote from: trobbins on October 04, 2022, 03:25:47 amYou need to make sure the !/ in the end is also copied to the url in the browserhttps://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details!/

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 04, 2022, 11:17:05 pm
content: Don't remove any more potting until you read the post referenced. You can make the job orders of magnitude harder if you mess up the wiring hidden in the potting!!!https://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details!/Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 05, 2022, 12:03:38 am
content: Thanks Corby - agreed.From the photos in that linked thread it is unclear how the DB9 cable extends down into the foam, and then how the lamp heater and thermistor wiring exits that DB9 cable. It appears that the DB9 cable continues down through the insulation (and located between the magnetic field coil and the heater winding) to the cell oven and doesn't get located in to the machined groove in the lamp oven aluminium cylinder - do you recall ?I am just mulling over my options, as I am not keen on completely removing the aluminium cylinder if I don't have to. One possibility is to excavate the outer wall of the aluminium cylinder down to where the groove starts, especially if that doesn't physically impinge on the existing thermistor. I may then be able to insert the new heating turns such that heat is transferred through the upper-half of the aluminium cylinder, and use the cylinder to then even out the temperature for the lamp assembly. That does assume that the remnant of the existing lamp oven heater wiring (the common +22V end) can be isolated from touching the cylinder wall.Ciao, TimCiao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 05, 2022, 04:16:30 pm
content: Tim,Either way you will lose the original connections to the Db9 and have to route the new lamp oven wires out to the Db9 on the end of the cable. If you remove the cylinder you also lose the original thermistor wires and they would need rerouting also.The problem with digging down into the "exclusion" zone is that there is no guaranty that you can avoid damage to the cable as it could be very near the top!As far as removing the cylinder I just finished rewinding one and rather than machining complete grooves I just made the 9 grooves in just the exclusion zone area so that the new windings could be flush. Only took a few minutes with a hacksaw and a dremel to widen the slots a bit.The existing +22volt end can be disconnected inside the Db9 shell on the cable end.The original machined slot was for the thermistor only, it does not involve the cable.If you proceeded like you were going to remove the cylinder and removed the potting as in the post you might be able to make a heater "insert" that would slide down into the opened up area?Cheers, Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 05, 2022, 10:51:54 pm
content: Yes my first option was to see if it made sense to prepare a slip on 'voice-coil' type cylindrical assembly with just the heater. Stanley has kindly just sent me some of his wire, so I will explore what can be done with that later next week. I do have 5 ohm/ft Advance resistance wire but it isn't insulated, which makes that path difficult. I have thin Nomex sheet/paper that I could use as either an inner or outer form. Preferably the bifilar twisted insulated resistance wire has margin between turns, like with your groove setup, so I need to assess what margin I can achieve between turns versus the depth of excavation (and hence risk of upsetting the thermistor). A portion of the existing heater may still remain, so I need to see if that can be isolated, as one end will be connected to the +22V that is also connecting to the cell oven heater.One unknown is the maximum temperature reached by the resistance wire, either as an initial peak during heat-up, and as a continuous level, given that the aluminium cylinder is controlled to 90-92degC. There will be some nominal thermal resistance between the wire and the cylinder which will mainly dictate the continuous operating temp of the wire. Nearby materials like silicon rubber (engineering grade or RTV) and Nomex are rated to a bit of 200C. I may even have room for a thin layer of neoprene or aerogel to further buffer the heat flow, although just an air cavity is simplest as you have used.In the interim I am going to assess if the exposed filament exhibits damage just towards the 'top' portion, or if the enamel (I assume) coating has degraded all the way along the cylinder.Ciao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 06, 2022, 04:05:13 pm
content: Tim,As I said the +22 volt wire can be disconnected in the connector shell so that is not an issue.The thermistor is buried in the slot about midway down so you should not encounter it when you "dig"If you can safely excavate enough material around the top I'd just coil up the 9 or so turns of the twisted wire, stuff it in and RTV it in place.Note I use ASI 388 electronics grade silicone RTV. Make sure your RTV is NON-corrosive!It's a little more work to get the cylinder out as per my post but it is way better than messing up the other wiring!Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 06, 2022, 10:11:44 pm
content: Corby - thanks, I had forgotten that two heater wires join at DB9 pin 4Agreed about the type of silicone rubber - at the moment I only have an engineering grade (selleys 401) tube open, and it is acetic cure.Ciao, Tim

author: trobbins
author_rank: Frequent Contributor
timestamp: October 14, 2022, 12:02:10 pm
content: Touch wood I have jumped the lamp oven repair hurdle. Photos and a description inhttps://www.dalmura.com.au/static/HP%2005065-6001%20lamp%20heater%20repair.pdf. Thanks to Corby and StanleySoon after the three ovens started to regulate I noted a burning aroma and saw that the supply meter reading had dropped, and the A15 board parts were getting very hot, with one inductor cracked/burnt, so now on to the next repair hurdle (but hopefully just simpler electronic fault finding).Photos from my first hurdle - repair of the 00105-6013 crystal oven oscillator are inhttps://www.dalmura.com.au/static/HP%2000105-6013%20internal%20wiring%20info.pdf.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 14, 2022, 03:23:20 pm
content: Tim,I'd check for a short somewhere. Unplug the A11 until your A15 is working. Then I'd monitor the +20V current with and without the A11.You may be able to Ohm out the problem.Which choke was burnt?Cheers,Corby

author: TheSteve
author_rank: Unknown
timestamp: October 14, 2022, 03:46:50 pm
content: Every time I see an update to a 5065A thread I want one just a little bit more...

author: edpalmer42
author_rank: Super Contributor
timestamp: October 15, 2022, 01:32:12 am
content: Quote from: TheSteve on October 14, 2022, 03:46:50 pmThe last one that sold on fleabay went for C$6500. How deep are your pockets?

author: TheSteve
author_rank: Unknown
timestamp: October 15, 2022, 01:54:19 am
content: Quote from: edpalmer42 on October 15, 2022, 01:32:12 amI saw that. I'd be more interested in a broken unit to rebuild - hopefully a little cheaper. I do have spare 3458A's, maybe someone will want to trade some day.

author: edpalmer42
author_rank: Super Contributor
timestamp: October 15, 2022, 05:36:56 am
content: I've always considered an Efratom FRK / M100 or Stanford Research PRS-10 to be a good second choice to the 5065A.

author: trobbins
author_rank: Frequent Contributor
timestamp: October 15, 2022, 11:56:21 pm
content: Arrrgh, testing on my instrument now shows two new issues.Firstly the cell oven heater circuit now appears to have a fault - exhibiting itself as a zero meter reading when cell oven was selected and power applied to the instrument - this wasn't displayed as faulty during earlier testing. Further testing showed the heater path measures 52 ohm cold, but effective resistance falls when voltage across it is increased (using a separate supply feeding just that heater). This appears to be a more onerous fault to fix, as there are no photos or posts on that process, and a risk of disturbing the microwave cavity (?) and then needing to retune that (from post #14 above).The second fault appeared once the lamp oven had reached regulation temperature. The lamp circuit +20V feed passes through inductor L2 on the supply regulator pcb A15, and on inspection that part had burnt/cracked - once L2 was replaced the A15 board was checked and presented as ok. The +20V feed current to the lamp circuit (A12A1 spectral lamp oscillator board) was then monitored and a low resistance circuit appeared once oven temp started regulating. The main 2N3553 Q2 had been previously replaced/repaired as part of an initial repair effort a few years ago by the owner, so I guess that transistor, along with the parts in series with it (that would have also been stressed from a low resistance circuit path through Q2) will need inspection/replacement.So one step forward, but two steps back

author: trobbins
author_rank: Frequent Contributor
timestamp: October 16, 2022, 06:59:21 am
content: Corby, or anyone who has repaired Q2 (2N3553 in TO39 can) in the lamp oscillator assembly, I'd appreciate any comment on how the TO39 fitted into the Thermalloy 1101A heatsink fitting and then to the oven aluminium oven cover plate. When I opened up my Q2 heatsink, the 2N3553 can wasn't insulated from the 1101A in any manner except for thermal grease, and the 1101A stud wasn't insulated from the aluminium cover plate of the lamp assembly, so I'm presuming the observed low resistance fault was from the TO39/1101A to oven ground due to the previous repair not being properly finished. The 2n3553 itself tests ok, and even tests ok at up to 95degC (in a thermal chamber), but I was just using a simple uP transistor checker. The other parts test ok, even though they look very heat stressed.Q2 and 1101A assembly, with plastic spacer used between assembly and pcb.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 16, 2022, 04:08:49 pm
content: Tim,The original fitting was done without any added insulation.The heat sink anodizing was the insulation.I have seen later lamps that use an insulating washer that fits into the hole to center the stud on the outside of the lamp similar to washers used on power transistors, some are nylon or fiber and some are thin black anodized aluminum.You need to grind off the emitter tab to make it smooth and flush or when you tighten down the hex ring the tab will dig in and short out to the stud.When I have to replace one these days I don't use heat sink grease on the stud. I use a silpad insulating heat sink pad on the inside and the mentioned insulating washer on the outside.Make sure you tighten down the stud and make sure the leads engage the board properly first before soldering the transistor in. Tightening the stud with the transistor soldered in can stress the leads!If the1.3K resistor is original you should replace it as they will eventually fail. I use a 1 or 2W MOX 1.3K 2%.Cheers,CorbyCheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 16, 2022, 10:39:12 pm
content: Thanks for response Corby.Yes the TO39 can emitter tab was intact, so likely was the presumed point of electrical interconnection arising from thermal expansion (given the low resistance path did not exhibit itself initially). I'll remove that tab, and install a typical power device stud mount insulation scheme, and swap out that resistor, refit the lamp assembly and confirm all is then good at that end of the optical assembly.Do you have any comment on what to expect at the other end of the assembly if I remove the outer metal cover cap? I can anticipate that accessing the cell end of the assembly is fraught with risk, and even a technical inability to recover the cell performance needed for adequate operation, but I have hit a brick wall with this restoration otherwise.Ciao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 17, 2022, 12:10:38 am
content: Tim,Accessing the cell end is not a big deal.However I'd wait until you get the lamp running. With the lamp working and the cell and lamp ovens up to temp hopefully you will be able to see on a scope (A7 TP2) some 2nd harmonic signal when "on frequency". If you can see even a tiny bit then you can try optimizing the A3. Turn the top two pots max CW and then see if you can get more by tweaking the two matching capacitors and the varactor bias pot. on the side. If you see 100Mv P-P or more on TP2 then turn the rear pot on A7 to give you 30 on the 2nd harmonic meter reading. Then log the reading daily for a week and see if it's slowly increasing. If so let it run until it stabilizes. At that point if you have >700-800Mv at TP2 then do the rest of the alignments. The cell end is good enough at that point. If not I can give details on opening the other end and tuning the cell.Make sure the 2 matching capacitors are not frozen. If frozen and you turn them you can break the rotor loose from its connection. I usually lever a plastic shaft between the hole in the cover and the top edge of the capacitor. Apply pressure at a couple spots around the rim until you hear the rotor snap loose.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 17, 2022, 12:39:57 am
content: Thanks again Corby. My concern is not appreciating what to expect from the open-circuit cell oven, and whether repairing that cell oven heater could cause me grief with the cell operation just by way of repairing the heater. Ciao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 17, 2022, 06:02:40 pm
content: Tim,I thought the cell oven was good and you repaired the lamp oven?If both heaters are good now you should be able to power up ,assuming you located the cause that loaded the power supply down.You can pull the 3 caps off the cell end and look in but there is no need yet if the ovens are both good.One thing to do if you haven't is to Ohm out the TED wires, the tightly twisted black and red wires from the cell end. It should read close to a short.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 17, 2022, 10:58:44 pm
content: Corby, yes the cell oven was initially working but appears to have now stopped (open-circuit heater) during the latest test. I had confirmed the lamp oven was working and was starting to confirm normal operating conditions for other circuitry, and sadly then observed both the cell oven fault and the cooking power supply inductor feed to the lamp oscillator (which I have repaired and replaced the 1k33 part and will get a chance to test tomorrow). Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 18, 2022, 09:58:43 pm
content: Tim,How unfortunate! If the C-field winding is still good and the cell thermistor is also good I'd consider removing the lamp cylinder per the instructions and seeing if the cable in the exclusion zone was damaged. The first couple times I removed the lamp cylinder I did damage the cable but was able with much care get the break spliced. Since then I have done several without any damage by observing the exclusion zone.If that doesn't work you would need to consider rebuilding the cell oven also.Here is a PIX of an optical unit that I had to rebuilt both ovens and rewind the C-field.If it's possible to get the cell oven removed without damaging the C-field that would save some effort.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 18, 2022, 10:34:05 pm
content: Thanks for advice and photo Corby - much appreciated. That gives me a better appreciation of how the heater wiring, thermistor wiring, and C-field wiring span out from the DB9 cable in the zone between the two oven cylinders. That in-between zone of foam is now hard baked foam, and is presumably where the DB9 cable wiring splays out.The cell heater now shows correct continuity, so I will aim to check that the lamp circuitry works, and monitor the cell heater operation to see if and when it becomes open-circuit again (presumably related to thermally induced movement). If it goes open circuit then I may be able to garner some insight on where the break is occurring from capacitance readings between cell heater cylinder and heater wiring ends.Ciao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 19, 2022, 03:24:55 pm
content: Tim,Check the wiring to the cell heater inside the Db9 connector, if that's OK monitor the continuity while flexing the cable.I'm hoping it's external (outside the potting)!Cheers,Corby

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 20, 2022, 01:05:09 am
content: Tim,Also check which wire you disconnected from pin 4 of the Db9!Originally there should have been a Yellow and a White wire.The Yellow goes to the cell and should be connected. The White goes to the lamp and should be disconnected as you have a new lamp oven.Pin 5 (Gray) the other lead to the lamp oven should also be disconnected.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 20, 2022, 06:14:46 am
content: Ta Corby, yes those were the wire colours on my DB9, and it was convenient to have them as separate wire feeds from DB9/4 - both for retrofit of a new heater (as the white and grey can be snipped a bit shorter but not risk connecting to anything else either in the DB9 or in the loom/oven), and for faultfinding. Just trying to progress another restoration and then back to the 5065ACiao, Tim

author: trobbins
author_rank: Frequent Contributor
timestamp: October 24, 2022, 02:21:36 am
content: Hi Corby, I'd appreciate your insight to the following please.I took some time to confirm and fault-find operation of the cell heater, given the preceding lamp heater repair and lamp assembly repair. With the optical assembly out, both heaters tested fine by themselves and regulated fine when connected using the DB9, and also when the repaired lamp assembly was refitted. But when the optical assembly was fully installed (with connections from the cell end reconnected) there was a cell heater fault. I confirmed the related circuits were ok (cell heater controller on A11 and its main chassis mount transistor; the logic circuit A14; and the metering path via A17 terminal board). So I then backtracked and removed the cell end connections and revealed that the cell heater (at the controlled end) is shorting to the ground shield of the CR1 harmonic diode in A12 RVFR, and so shorts to ground when that coax feed connects to J4 on A3 Multiplier assembly. By resistance I can identify the short is not at the +22-28V end of the cell heater.Removing the three end covers at the cell end, I can see that the CR1 connection shield is mounted to the cell metalwork, and the CR2 photo diode appears to be isolated from the metalwork (which concurs with resistance measurement of its shield), and TED also appears to be an isolated circuit. So it does seem that one end of the heater coil is shorting to the cell oven aluminium cylinder, and hence is shorting to equipment ground via the CR1 harmonic generator cable shield.From your photo in post #60, the cell oven cylinder is quite long. The thermal insulation around that cylinder at the cell end seems to be rock hard, but I guess it could just be that the surface face is solid and thick and so presents as being quite hard. I'm now assuming that I could do a similar style of heater repair (as to what I did at the other end for the lamp), and gouge out a channel around the aluminium cylinder but only go to a similar depth of 27mm and so leave the cylinder hopefully undisturbed (along with the cell etc) and still solidly locked in place by the remaining insulation. The heater leads would have to route to the DB9 outside the whole assembly, and the main risk would then be any disturbance to the cell heater thermistor.Ciao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 24, 2022, 03:31:36 pm
content: Tim,That's a bummer!I've never seen a cell end short out that way!I think you will be safe going down to the 27mm depth without encountering any other wiring.Stay close to the cylinder and don't mess with the potting around the outside edge (red) as the C-field coil is there!The first 1/4 inch or so is usually hard, as you go down it gets a bit easier to get out.You could take drill and drill out the majority staying right up against the cylinder, then get the remaining stuff out with a screwdriver.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: October 25, 2022, 06:29:22 am
content: Thanks for looking Corby. Stanley is sending me the same insulated heater wire again, so I'll start digging when that arrivesI added a 200mA in-line fuse in the dc feed to the A12A1 lamp oscillator from A15 as it drew over 1A for the previous fault but doesn't run above about 150mA max.

author: TheSteve
author_rank: Unknown
timestamp: November 02, 2022, 03:37:24 pm
content: Decent looking unit sold for $2555 this morning before I woke up - did anyone here get it?Seller did say they let some smoke out...

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 02, 2022, 04:10:55 pm
content: If that was the one on eBay with NASA stickers it was a very old SN prefix 968, I would not pay that much without verifying that the lamp oven has not melted down! It was in nice physical condition. Had the older Quartz oscillator but good that it had the series 6080 A7 module.Cheers,Corby

author: TheSteve
author_rank: Unknown
timestamp: November 02, 2022, 04:20:48 pm
content: That is the one. Perhaps good I slept through it then. Finding one will likely be a long term project.

author: trobbins
author_rank: Frequent Contributor
timestamp: November 08, 2022, 12:22:53 am
content: Thanks to Corby and Stanley the 5065A now has functional optical assembly heaters. The unit has been on for less than a day so far, so no 2nd harmonic meter signal yet. I'll give it 2 days and then start the TED process for a flooded cell if no 2nd harmonic signal.In the interim I'll check the performance of the A7 signal amp module that amplifies then frequency selects the 137Hz and 274Hz signals. My A7 module is the 6010 version (series 916) which is not the same as the Manual's 6080 version (series 820) that I have been using, but I tracked down the 6010 info in the on-line hp5065a_part2.pdf, as well as Corby's comment that the 6010 was the first version and quickly upgraded by HP as it has some performance limitations.I'll use a battery powered low level audio sinewave source via 10Meg into the input J1, and use my REW/soundcard frequency spectrum analyser to check the output of the first stage amplifier at TP2, and then the frequency filtered outputs at Y and WBO outputs. I can then confirm gain from TP1 to Y output is 10-40x for ok loop gain. I can also confirm Meter response for 2nd Harmonic by adjusting sinewave signal. I think I can then check that the Error signal (via A8 detector) functions with 137Hz level, and check the CONTROL meter level for both Loop Open and Operate conditions, and possibly confirm the output of the OCXO shifts with EFC signal (although I only have a 1Hz resolution on my frequency meter so would have to set up the GPSDO and look for phase shift on a scope).Just quickly using a DMM I note that TP2 has a +4.3Vdc unbalance, which seems a titch excessive. The manual has a procedure for measuring residual DCV at J1 (which is meant to be less than +/- 5mV), as well as a procedure for measurement of A7Q1 base DCV (which is J1 input as well) and tweaking that to within 0.5mVdc. I measure 3.4mVdc at J1, so perhaps no immediate need to adjust the internal R3 trimpot (apart from the 4.3V offset) given that would require removal of the module as R3 is not easy to get to, but I guess I will do that tweak.One issue I notice with the heaters is that the Lamp oven meter reading is still swinging from 10 to 42 with a 7 second period, and hasn't stabilised like the other two ovens. I'd guess that is due to a degraded part on the A11 temp controller pcb, rather than due to a changed thermal delay in the heater and thermistor physical coupling - any thoughts, as I'll have to try and fault-find thatCiao, Tim

author: trobbins
author_rank: Frequent Contributor
timestamp: November 08, 2022, 07:18:18 am
content: I've just used REW software and an EMU0404 soundcard for signal generator and spectrum analyser assessment of some aspects of the 5065A, with signal injection to the A7 AC amp J1 input (in lieu of the optical cell) via 10M and ground clip.A7 AC Amp module J1 input stage to TP2 shows low harmonics for 0.5Vpp in, with +5.4dB gain. TP1 shows 0.14% H2 with +0.7dB gain from input, and clearly shows the 274Hz notch in the noise floor response. Y output clips for signal levels above ~0.19Vpp at J1, and non-clipped output has low HDs.As Corby indicates, the 6010 version of A7 presents a 2nd H meter level even for 137Hz signal, and meter level varies with 234 and/or 137Hz magnitude.With 137Hz signal input, the following A8 Phase detector module generates an Error meter reading that cycles between -50 and +50, and the reference 137Hz oscillator shows sync with external REW signal at 137.035Hz so is ok.Switching from Open Loop to Operate mode shows the Control meter reading swings and the Integrator Limit indicator lights at <-50, and >+50, and the A9 Integrator output to OCXO EFC- control line cycles from -14.4V to +7.8Vdc, and my SD6250A frequency counter just recognises a change in the 5MHz frequency (which is below the 1Hz resolution of the meter, but identified by toggling of the last digit).I was also able to confirm the 1MHz and 100kHz outputs are ok, and the A3 multiplier module has 5.4Vdc on TP2, so that aspect is ok.The Lamp Oven meter swing has subsided a bit to between 15 and 38, so moving in the right direction.Ciao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 09, 2022, 04:11:28 am
content: Tim,Since the original lamp thermistor is being used your cycling is most likely the poor coupling between the thermistor and the oven. This as your modified oven heats only at the top and the thermistor is at the midpoint height wise. I would not worry about it yet as the instrument should operate in that configuration.For cell flooding I use a 5VDC fixed supply through a 5 Ohm 10watt WW resistor to get the 1Amp. While watching A7 TP2 with a .25Hz offset in open loop adjust the A3 varactor bias pot and the two matching caps to see if you can find a signal. IF not hook up to de=flood the cell, let it run a week and try again.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: November 09, 2022, 05:28:44 am
content: Thanks again Corby. Could you please elaborate on the A7 TP2 checking process with respect to the following.I have a 6008 version of A3, so I'm not sure how aligned that is with the 6078 version module - for the 6078 version schematic I can identify varactors CR3 to CR6, and it looks like they have a bias pot R11 "Mod Level Adj" applied to the incoming 137Hz signal from A8 phase detector. I can also identify trimmer caps C61 and C59 that would match the signal output going to the RVFR via J4. Are those the adjustments you were referring to?I can monitor A7 TP2 using my spectrum analyser to identify any 137Hz and 274Hz signal levels. Is that the intent, and if so then is the aim to get a max level of 137Hz at TP2, or just to see some signal above the noise floor ?I am not sure what your reference to 0.25Hz offset means ?Overnight the Meter reading for 2nd Harmonic moved off zero and is now about 5. The unit has been on for 48hrs now.Ta, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 09, 2022, 06:55:23 pm
content: Tim,If you adjust the 5Mhz output (in open loop) for 5.00000025 MHz that should give you a usable level of the 137Hz to see on the scope at A7 TP2. Just use a scope at 100mv/Cm.Once you are able to see that signal (after adjustments) then you can adjust the frequency to zero offset (5.00000000Mhz) and observe the 2nd harmonic signal. You would like to be able to get at least 500mv P-P.Intent is to get max 2nd harmonic level at A7TP2 when at frequency.If nothing is discernible run the TED at 1 AMP for a few days while monitoring A7TP2. Hopefully you will see the 2nd harmonic slowly increasing in amplitude.On the A3 turn the top pots R3 and R11 max CW and the side bias pot R40 and matching caps C59 and C61 for a max level at A7TP2. Start with R40 max CCW and turn it CW while looking for a signal. This usually will occur within the first half of the pots range. Also measure A3 TP2 for around 5VDC.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: November 16, 2022, 12:43:11 am
content: Hi Corby. I applied the deflooding current to the TEC for 3 days. In loop open, the A7 TP2 spectrum signal was then tweaked for a null in 137Hz using the oscillator fine tune adjust and the 274Hz then tweaked for max level using the various A3 trimmers you indicated. Some of the A3 trimmers are quite sensitive, although the REW spectrum analyser makes it easy to confirm trim peaks (rather than use the Meter 2nd harmonic level). The maximum 274Hz signal level achieved was about 80mVrms (290mVpp), which relates to a 2nd Harmonic meter reading of 24, and the 137Hz signal was at least -50dB below that, and the 4th harmonic about 19dB down.Switching to Operate mode, and resetting the logic gives a Continuous Operation light, and the control and error levels remain at zero reading. Interestingly the A7 TP2 spectrum shows the 137Hz level increases to only a few dB below the 274Hz level. The oscillator fine tune adjust continues to allow the Control level to be moved either side of 0. All the meter readings appear nominal although the lamp oven reading is still swinging slowly, and the cell oven reading is swinging very slowly, both of which you indicate would be related to the physical separation of the new heaters to their respective thermistors.I have noticed the 2nd Harmonic meter level glitches higher every now and again. I tried to identify if that was a coax connection issue, but that wasn't consistent. A glitch doesn't align with any perturbation of the A7 TP2 signal level. The owner did recall having to replace some leaking tants in a shielded assembly, so I will remove A1, A3, A7, and A13 assemblies and inspect internal parts, as the thought is it may be a supply rail bypass tant failing.The green indicator is also turning off after some time, but can then be reset. The instant of turn off seems to align with the lamp oven meter reading swing to its maximum (which is nearly 50) - given the A14 logic circuitry is 'instantaneous' for an out of range oven signal voltage, that would seem to imply that is a good place to focus on. Looking at the A11 heater control circuitry, I'd anticipate that either the bridge circuit or the doubler rectifier circuit could be places to modify the open-loop response to try and attenuate the peak-peak swing level without hopefully changing the average level of control voltage that controls the heater. At the moment the open loop meter swing period is about 10 seconds, so one thought could be to introduce a new RC after R26 (between Q6 base and the doubler positive rail) of say 10k and 220uF (2.2 sec time constant) with the risk that the 10k would shift the Q6 dc level and hence the lamp temp. One hassle is the optical unit would need to be removed to allow a temp probe to assess if the lamp temp was shifted. Any thoughts on this?Ciao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 16, 2022, 04:52:32 am
content: Tim,You can turn the rear pot on A7 to set a new reference level for the 2nd harmonic meter position. Usually between 35 and 40.Once set you can monitor the 2nd harmonic meter for another couple days. If the reading is stable you can reconnect the TED to its normal spot. If still increasing wait till it stops before reconnecting.The older A7 actually nulls the 2nd harmonic meter reading at the center frequency and rises if you go either way off frequency. This is because it does not have a bandpass circuit in the 2nd harmonic channel.I'd suspect the A7 for the meter glitches but since your 2nd harmonic level at TP2 is 290mVpp it could just be noise getting in. If you use a scope at A7TP2 what 2nd harmonic level do you see?The operate lamp circuit will indeed turn the lamp off if the either oven is at max. This is normal.One thing you can try to eliminate the oven oscillations is to connect a decade box (#1) in parallel across the pins on A11 for the lamp thermistor. At the same time pull A11, open one end of the lamp temp setting resistor. Connect two wires to bring it out to another decade box (#2) set to the original resistor value and reinstall A11. On the other decade box try starting at 2K and work down to maybe 820 Ohms. You will have to insert a thermocouple probe into the lamp end to monitor the lamp temperature and as you make changes to decade box #2 readjust decade box #1 to maintain the correct temperature. You want to be around 92 degrees C.You can set the optical unit as shown in the pictures so you can work on the lamp end. Extenders are used for the Db9 connection, the lamp power, the cable to A7 and the TED wires. You can't use an extender for the cable to A3 but the original wire will reach.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: November 17, 2022, 06:49:40 am
content: I found a heat damaged R48 (51 ohm) on the Y output of A7 when inspecting inside the A7 assembly. Although the series connected 60uF tant C24 measured ok on my LCR, there was leakage going on when the assembly was powered on the bench and the dc voltage on output of IC2 was measured and Y was grounded. Otherwise A7 voltages were nominal, so those two parts have been replaced.I have restarted de-flooding - initial duration was 3 days, so as suggested I will monitor 2nd H meter level and see if it stabilises over coming few days - it is nearly 30 now (Continuous Operation). So far there has been no 'glitching' behaviour so here's hoping that aspect has been solved.As before, the heater reading on the meter is swinging and nearly reaching 50, but hasn't stopped continuous operation yet. There may be a causal link to local ambient and that the top and bottom covers have been off all the time. Once deflooding is finished, I'll put the covers back on and see if that suppresses the meter swing.One additional thought is that if the heater meter swing is not adversely affecting stability performance, then the signal level to the A14 logic board could be a simpler target to fool by introducing an RC time constant that suppresses the peak-to-peak swing of the heater signal reaching the logic, but otherwise allows a continuous fault low or fault hi to annunciate itself. That path doesn't then alter the pre-existing thermistor setting and regulation control.

author: trobbins
author_rank: Frequent Contributor
timestamp: November 20, 2022, 02:54:38 am
content: I continued the de-flooding process for a few more days and was able to get the A7 TP2 level of 2nd H up to 150mVrms (ie. circa 420mVpp).I then returned the TEC wiring to nominal and put the 5065A in continuous operation - for about a day now. After half a day I reset the 2nd harmonic meter level (A7 R19) to about 25, as it had slowly subsided to the point of the logic tripping out of Continuous Operation. I've just checked the 2nd H level and it has reduced from 150mVrms to about 65mVrms, and that was once the various A3 trimpots had been optimised again for max 2nd H. Perhaps that indicates that the de-flooding process still needs to continue?With the 5065A in open loop, and the OCXO fine tune set for zero error and a null of the 137Hz signal in the spectrum on A7 TP2 (137Hz <-45dB below 273Hz), a comparison of the 5065A 5MHz output to my GPSDO shows negligible roll of down below 240 secs per 200ns full-cycle sine, so circa 200n/240 = 0.8 ppb, and below the 1ppb that the GPSDO is indicating it is within.Corby, what I don't understand is that when I switch to continuous operation, the A7 TP2 spectrum shows that 137Hz signal rises to within a few dB of 273Hz, and control moves to -14 on the meter and the 5MHz shifts to about 0.01Hz over the GPSDO (one 200ns cycle roll in about 25 secs). Any thoughts on how I can check why the control is pushing the OCXO off frequency ?Ciao, Tim

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 20, 2022, 05:23:35 pm
content: Tim,If you de-flood too long you can overshoot!If so once you hook the TED back to normal the signal level will drop slowly till it stabilizes at the new level.It does sound like you have an offset. Check the zeroing adjustments for A9.Have you checked the phasing of the 137Hz? Try checking using this procedure.Cheers,Corby

author: trobbins
author_rank: Frequent Contributor
timestamp: November 23, 2022, 01:53:39 am
content: Corby, thanks for the procedure doc - much appreciated.In open-loop I set the OCXO fine adjust to just get 273Hz on A7 TP2, although the signal level was only 100mVpp. I went through the A3 adjustment procedure a few times but can only achieve a max A7 TP2 ac voltage of about 140mVpp, so nowhere near 500mVpp.With the A8 sync adjustment, I had gone through that before but had not observed the simple half-sine waveform, but rather a higher frequency and noisier signal, but still showing the 'splitting'. With respect to your notes, the fine freq adjust does vary the level of splitting and that splitting can be effectively nulled (although the phase pot is at full CW), but the 'signal' is now just noise (and A7 TP2 is effectively the same 273Hz amplitude of about 100 to 120mVpp).With the loop gain setting procedure, I can only reach about -14 on meter error reading when fine tune is 50 units CW of centre frequency. My OCXO doesn't have coarse adjust capability, so the fine tune setting can't be easily made '250'. With the loop closed, the control voltage at the rear bnc is 0V at centre frequency, and goes to +0.8V at 50 units CW fine tune, and to -0.7V at 50 units CCW, so not quite +1 to -1V. The error meter reading swings from -14 to +14 respectively. With the fine tune back at 50 units CW, and loop operate switched on, the error falls to 0.The next adjustment of meter 2nd harmonic level is ok, although the meter needle has some fine jitter of about +/-1 about 35 setting, and A7 TP1 is still about 100mVpp.Control is now at +10 meter and +0.8Vdc rear bnc, and the 5065A 5Mhz output is now within 1ppb of the GPSDO. So no 0.01Hz difference that was observed a few days ago, and on review that seems to be a result of not moving the OCXO fine tune to 50 units CW of centre frequency.Any thoughts on why the 2nd H level from A7 TP2 is relatively low? Perhaps I should wait a week or two and confirm if that level changes.I don't have access to a frequency standard but will now try and see if the scope phase shift of 5065A to GPSDO can be minimised using the magnetic field adjustment 10 turn pot, given the op manual indicates that adjustment has a nominal 2ppb span (increasing the pot increases the 5065A frequency).Ciao, Tim

author: trobbins
author_rank: Frequent Contributor
timestamp: November 23, 2022, 12:02:52 pm
content: Well I'll be damned ! Now at 400mVpp 273Hz on A7 TP2 - I even had to reset the 2nd H meter level as it was over-ranging.A possible catalyst was that I had to turn the unit off to repair the magnetic coil current supply (failed A15 Q6 dual npn) for a few hours. So with a goodly level of 2nd H I have just been setting the magnetic 'clock' for negligible drift against the GPSDO - down to a level where the GPSDO tracking jitter is circa 0.1ppb (https://www.eevblog.com/forum/projects/budget-gpsdo-a-work-in-progress/50/.So I think I am pretty much done with my repair log - touch wood. Thanks so much to Corby for the tireless assistance, and to Stanley for helping with the heater wire supply.Ciao, Tim

author: HighPrecision
author_rank: Unknown
timestamp: November 24, 2022, 11:50:26 am
content: Quote from: trobbins on November 23, 2022, 12:02:52 pmSame failure fixed on my unit:https://www.eevblog.com/forum/metrology/inspecting-aligning-and-testing-an-hp-5065a-rubidium/msg3271248/#msg3271248Best, Stephano

author: trobbins
author_rank: Frequent Contributor
timestamp: November 24, 2022, 12:42:47 pm
content: Ta Stephano - I breezed through that thread at the start of the journey, but one then gets blinkered by the immediate faults being faced and forgets to sweep through all the threads again - and yes it makes sense that the correct line wasn't being used given the abnormal scope waveform I had when checking phasing. In this case the repairs were being done iteratively as functions were being checked, and the magnetic field repair was the last function to check and repair. And as the ops manual points out, the loss of magnetic field is not monitored by the Continuous operation indicator and logic. I really should go back and redo all the setup procedure again, but that can be for another day by the owner to enjoy

author: Whaleback
author_rank: Contributor
timestamp: October 02, 2023, 12:44:51 am
content: Hi folks. There was a recent group of 5065As that surfaced on the auction site all from the same seller.I gambled and got the first one listed with option 3 in "parts or not working condition". It arrived and I started meticulously cataloging its condition.The serial number is 0956A00250. It looks like it was reconditioned at some point, as it has a 10811 OCXO, the digital clock/PPS option, and what appears to be a later era RVFR.The first problem is that it is missing the A13 buffer assembly. So I have no way to close the servo loop if the physics package is still ok. Is that something I can jumper over (A3J3 direct to A1J2) temporarily?I removed all the circuit cards (they're all there). Unbelievably, there's no corrosive cap leakage on any of them. I will be replacing all the recommended devices anyway (electrolytic caps, hot diodes, etc).The A12 RVFR looks like it is a replacement. The housing is unpainted, and it carries an 05065-6071 part number as well as a 1220A02147 serial number.I ohm'ed out the DB9 and and the heaters were both 50 ohm, the thermistors both 2k, and the C-field coil was 11 ohms. No heater short the the chassis.I opened it up to find someone's greasy thumbprint on the filter cell that I'll clean up with an ethanol prep pad.I put 20V across the feedthru and the lamp module chassis, and it drew almost no current.I was sad. :'(Turns out the A12A1 R1 1.33k resistor was open. I snipped that out and soldered a temporary 1.3k across the PCB lands and it lit at nominal start and run current.So now that I know I have a unit that potentially is recoverable, I thought I'd log the bring up here? Should I start a new thread or append here?I also have a few items I need to source, primarily that A13 buffer module. I'm hoping some on list or over at Time-Nuts has one in a dead chassis I can buy or beg?Also looking for a complete set of side panels and handle panels, it's missing all 6. They're PNs 5000-0738, -0739, -0766.Does anyone know the part numbers for the spring metal clips that hold top and bottom cover fasteners on? I need 8 of those and the pozidriv screws. I can't seem to find a master HW part list for old HP gear.Finally , I really want to say thanks to Corby Dawson, Ed Palmer, maat, Timeok, and everyone who's dropped 5065A restoration knowledge here.

author: KE5FX
author_rank: Super Contributor
timestamp: October 02, 2023, 01:03:54 am
content: Very cool. I saw that listing -- guessing it was surplussed by Boeing given the seller's location and the other stuff he's listing. Nice to hear it has an updated RVFR, 10811, and a good home. I hadjust bought onefrom another seller for beaucoup bucks so I didn't feel like jumping into the fray for this one.If anyone is still looking for a unit in decent shape,this one is listed by the same sellerI just bought from. It's pretty spendy. No guarantees, obviously, but the only things that were actually wrong with the one I bought were a missing indicator lamp and a pair of open 20 uF caps on the RVFR heater controller board. Fortunately the RVFR heaters were OK. I think it has the best 10811-60109 I've ever seen; it does about 2.5E-13 @ t=1s in open-loop mode.

author: Whaleback
author_rank: Contributor
timestamp: October 02, 2023, 04:04:22 pm
content: Hi John - thanks for responding. Yeah it wasthis one. Same seller.I did find a donor chassis from a 8616A.Does anyone know the difference between the -6001 and the -6071 physics packages?- I see - from the manual it's a replacement unit.

author: Whaleback
author_rank: Contributor
timestamp: October 04, 2023, 09:47:13 pm
content: Lamp photo - temporary 2k6||2k6 installed at R1.

author: Whaleback
author_rank: Contributor
timestamp: October 04, 2023, 09:57:53 pm
content: Oven controller and PSU .PSU has some oxidation on the bridge diodes. One of the diodes is suspect as didn't measure correctly on the meter.I'm looking for recommendations on the wet tants across all the cards. I'm thinking about just replacing all of them in every card/assy.Do I use 'modern' dry pill tants? Nichicon/Chemicon radial electrolytics? All sources of high quality axial al el caps appear to have been retired.I don't plan on ever returning the battery back up to this unit. I'm planning on chopping out all the components on the charger board except for the ext/int DC or-ing diodes.

author: trobbins
author_rank: Frequent Contributor
timestamp: October 05, 2023, 12:36:33 am
content: FWIW, the early version of 5065A I repaired had only a few caps identified as faulty and replaced, and I did check a few given that they were plausible fault initiators. In summary:05065-6024 RVFR temp controller A11: C23 and C24 had both gone bad (low uF and high R).05065A-6010 Signal amp A7: C24 (60uF tant) appears to be leaky when grounding Y. C18 had already been replaced.So in general, I wouldn't immediately replace all tants unless the first few you suspect due to a known fault, end up measuring bad. But that is just my view from a single sample of equipment.

author: coppercone2
author_rank: Super Contributor
timestamp: October 05, 2023, 12:47:26 am
content: can the physics package of one of these be improved by modern insulators like aerogel ?

author: KE5FX
author_rank: Super Contributor
timestamp: October 05, 2023, 05:29:34 am
content: Quote from: Whaleback on October 04, 2023, 09:57:53 pmYou should be OK replacing the tantalums with modern 105C aluminum electrolytics. I don't think it's worthwhile to declare a general jihad against all of the hermetic parts, though -- just do visual and ESR checks and replace any that look suspicious.I do replace all of the 10 dry non-hermetic 100 uF parts when overhauling one of these, plus the two 20 uF parts on the oven control board.

author: Whaleback
author_rank: Contributor
timestamp: October 05, 2023, 02:17:57 pm
content: Thanks for the useful guidance guys.So my plan is to replace all the caps that Tim and John have mentioned, as well as some rectifier doides, and after checking, some other aforementioned devices that are known to be suspect such as C-field Q6, C5A/B, the chassis electrolytics, etc.My initial steps will be to test the main PSU alone on the bench, fix any deficiencies, install it and run only the 10811 initially while measuring it against my SRS FS740 to check its health. I am aware the adev will be masked by the FS740s internal PRS10.NOTE: SRS FS740 works with timelab. I have matlab or octave stream data off it to a file, then run timelab in 'Acquire live data file' mode. I'm happy to share the matlab script that does this. Anyone can code this up in python. It was just quickest for me to do in matlab.I built one of Corby's DMTD boards, haven't had time to integrate it in front of 740. This OCXO check is only looking for 'gross defect' behavior.Next I'll reinstall the oven controller and the RVFR and test the oven control. I am planning on installing a thermal fuse.Hopefully soon after that I'll have found an A13 module, and can start looking at closing the phase servo loop and continue down the path to a green continuous operation lamp.

author: Whaleback
author_rank: Contributor
timestamp: October 10, 2023, 01:13:27 am
content: Pics of bad caps. Some were ok, many were in the puffs and hundreds of ohms. I found a bad 1N4998 on the A15 PSU card so I pulled them all. I'll be jumpering over some of the diodes there and putting a bridge down on the chassis bottom as I see the newer revisions have. I haven't cracked A1/A3/A7, but bought replacement caps for them with intent.Couple of questions if anyone can answer:My RVFR tube is missing the fiber washer(s) I read about here. It sounds like there is only one? What is the intent of that washer? It's not thermal or electrical isolation right? There isn't one on the nut clinching _inside_ the outer shield, just direct metal-to-metal contact there? Can someone outline the fastener stack-up there so I can get it right? Is the fiber washer just that thick red kind-of cardstock material? Cork rubber?Does it need to be anything special? Can I use a delrin washer? Does it just provide drag to allow the nuts to clinch?Does anyone have a PDF of a manual more recent that the one i see all over for series 1908 in 1979? I bought the Artek copy, but its series 940.

author: Whaleback
author_rank: Contributor
timestamp: October 16, 2023, 01:22:09 pm
content: More debugging notes.Recapped all the 100u, 20u and a bunch of other caps. Replaced the oring diodes on the batt controller. Stripped the remaining circuits off the batt controller.Inserted A15 regulator and surprise - _no regulation_.After some careful analysis and poking around determined n-ch JFET Q4 was bad. Replaced with what I had on hand which was 2N4393. Not an ideal replacement, but it worked.Now have A15 regulating. Also have 2N4416A fets on order for proper cross replacement for that part.Installed thermocouple into RVFR. plugged A11 oven controller in as well at P15/J15 of RVFR.Monitored cell temp first - over appx 40 mins it rose and settled to 67.7C.Drew thermocouple out of oven until reaching new max temp at lamp oven of 90.1C.Temp regulation looked tight.5 and 1 MHz outputs looked pretty good. 100 kHz output looked terrible. High harmonics and subharmonic. Will be ejecting both dividers and all of the clock display HW unit later.Next steps are review performance of synthesizer, multiplier, and sig amp.Hopefully after that run, deflood, and adjust locking signals.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 18, 2023, 09:08:46 pm
content: The correct stackup for the threaded lamp post is:Once the first two shield ends are in place install the first threaded nut. I just look across the edge of the outer shield and position the nut so it just protruding. Then install the outer shield. With the shield pressed into place firmly the inner nut should just be contacting the outer shield. The fiber washer is then put on and the outside nut screwed firmly in place. The intent is to make sure the outer shield contacts the inner nut and after tightening against the outer shield functions as a heat sink. The fiber washer is to allow a little play with temperature. Fiber, card stock or nylon is fine.Cheers,Corby

author: Whaleback
author_rank: Contributor
timestamp: October 30, 2023, 02:30:58 pm
content: Thanks for that info Corby!So my current progress has found & replaced a failed 2nd harmonic buffer NPN - Q9 on the 6010 version A7 board. I replaced that and started the alignment.Progressed through the alignment, and everything worked out fine down to the phase detector board.I get a nice rectified sine at A8TP3 testpoint which as I deviate the fine frequency control switches sign after passing through a min amplitude as I cross the on-frequency point. Amplitudes are good down the chain, and phase splitting is symmetric.The issue I'm having at the moment is after switching into operate.When I dial the fine to on-frequency (null and noise only at the phase detector), and then switch into servo mode, the integrator swings and pins the meter immediately to the -50 end of its range.The output at A8TP3 shows the integrator has tuned the OCXO way away from the null.I have not yet started debugging this board, aside from checking diodes and BJTs. Those devices all seem ok. I haven't checked the dual-FET yet, or the ADI op-amp. I haven't checked the coarse or fine tuning of the integrator.I also haven't checked the neg EFC control on the 10811.If anyone has thoughts I'd love to hear them.I guess I should run through 5-29, 5-30, and 5-31 procedures before asking for additional guidance.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: October 31, 2023, 03:41:36 am
content: In loop open monitor the error meter reading.On frequency it will be zero.Move fine freq. CCW and frequency on a counter will go down and the error meter will move to the + side.Move fine freq. CW and the frequency on a counter will go up and the error meter will move the - side.If not make sure the plus and minus EFC jacks are not reversed.Cheers,Corby

author: bnz
author_rank: Regular Contributor
timestamp: October 31, 2023, 06:26:01 pm
content: I have not found the schematics, or at least the manual changes and list of replaceable parts, for the later A3 Multiplier Assay 05065-6106 (Series 2644) in any manual on internet up to now.Does anybody has seen that information somewhere?

author: trobbins
author_rank: Frequent Contributor
timestamp: October 31, 2023, 11:28:41 pm
content: Just noting that A3 in hp5065a_part2.pdf for -6078 for series 1420.

author: bnz
author_rank: Regular Contributor
timestamp: November 01, 2023, 08:37:30 am
content: Yep, I've seen that. But there seem to be substantial differences:

author: KE5FX
author_rank: Super Contributor
timestamp: November 01, 2023, 02:25:04 pm
content: Wow, 18 adjustments in this module alone.Far be it from me to call out HP for criticism, but... that just ain't right.

author: chuckb
author_rank: Frequent Contributor
timestamp: November 01, 2023, 07:35:40 pm
content: I'm in the middle of aligning a new series 2644A A3 module right now. It's a project!Corby posted the -2644A schematics and manual pages on the time-nuts forum a few years ago.Attached is the schematic.

author: chuckb
author_rank: Frequent Contributor
timestamp: November 01, 2023, 07:41:02 pm
content: The time-nut link for the Series 2644A A3 module, thanks Corby!https://febo.com/pipermail/time-nuts_lists.febo.com/2020-September/101338.html

author: Whaleback
author_rank: Contributor
timestamp: November 02, 2023, 04:07:27 pm
content: Corby - thanks for that. I checked the EFC+ and EFC- leads and they were correct. The problem was the position of the phase splitting pot.I had it set for beautiful split, at inverted phase. After winding it around to the correct polarity (at the end stop),UNIT ACHIEVES LOCK!I have three things remaining really to sort out:1) Neg 20 rail is at -19.7 when positive rail is exactly at +20. This only when A7 installed. When I disconnect A7 power, neg rail returns to -20 exactly. I have a concern something is still amiss in there.I expect the supply rails should track perfectly under good operating conditions, is that presumption incorrect?2) Phase splitting pot range winds out. I can't quite get to good splitting even after tweaking all of the drive and match pots/caps on A3. I'd really like to re-center the phasing range on A8 from the edge of the dial - is this an aging effect maybe from dried out caps on A8? Has anyone looked into this?3) The unit came with a 10811-60109 OCXO. When the unit is set to open-loop, the BNC control signal reads around 300 mV when tuned to on-frequency. Control drops to zero when I disconnect the 10811 EFC- SMB. When I swap out the 10811 for a 00105-6013, control is 0 V as expected. It appears I have an issue with the EFC- pin on the 10811? Has anyone seen this happen with units with a retrofit 10811?Gents - thanks for all the help getting this far!

author: Whaleback
author_rank: Contributor
timestamp: November 02, 2023, 04:53:29 pm
content: So I've been thinking about how I can contribute to this community. One thing I thought might be a nice to have could be a remote monitoring device for collecting "meter" data off the instrument and/or also tracking other testpoints.I'm thinking about designing a whole A17 replacement card with a LTC2499 24-bit 16-channel delta sigma ADC. ADC data is I2C, could also put in a 10k thermistor input and uC controlled latching relay to monitor A12 and cut heater power on fault. Or could use 67F100/102/105 instead of L version so no current in wiring unless fault. Anyone interested in this. I'd do the design in Altium and make it available at PCBway or OSH Park?I'm also considering a redesign on the PSU module around LT silent switchers and TPS7A4700/TPS7A3300 high PSRR low noise linear regs.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 02, 2023, 09:35:04 pm
content: The -20V supply is only regulated by two selected zeners in series. I would not worry about the absolute value. It only runs the A7 and is not critical.The phase adjust pot can end up at one end. As long as your splitting is OK that's fine.If splitting is a bit off try reducing (going CCW) on one of the two pots on the top of A3 (can't remember which one) until you can get proper splitting.If that does not work you need to apply an external 137Hz Through a 10Meg resistor to the input of A7.Monitor the output of the A7 where it comes into the A8 card connector. adjust the frequency of your generator for a peak amplitude. You are measuring the actual frequency if the A7 tuned circuit. Note it.Then return A7 to normal and adjust the A8 frequency to match. I have found that this will allow better adjustment of the splittingThe control signal is biased by the new arrangement used with the 10811, If you look at the old versus new loop gain procedure you will find the old one checks the control voltage on both sides of resonance. The new one only checks one side as the other side will not be balanced. This is not important in closed loop as the loop gain will cover both sides adequately.You might make sure the resistor arrangement was converted to the new circuit for the 10811, It has one resistor mounted on the standoff by the fine Quartz adjust vice the two in the old configuration.Cheers,Corby

author: KE5FX
author_rank: Super Contributor
timestamp: November 02, 2023, 11:48:25 pm
content: Quote from: Whaleback on November 02, 2023, 04:53:29 pmRemote monitoring is a good idea.I went down that road a while back-- having used an Arduino to provide thermal cutout support, it was easy enough to have it monitor photo current and 2H -- but didn't go any farther than that. Obviously its built-in ADC isn't in the LTC2499's league, but arguably you don't need that kind of performance unless you just want to go overboard. NTTAWWT.

author: bnz
author_rank: Regular Contributor
timestamp: November 05, 2023, 10:11:03 am
content: Quote from: maat on April 14, 2019, 02:25:02 amGood adviceI think these schould be promoted in the list of capacitors to check in the 5065A.

author: Uky
author_rank: Regular Contributor
timestamp: November 06, 2023, 08:40:46 pm
content: Food for thoughts:Since my 5065 A15 regulator board was badly corroded, I designed an improved regulator board.Using the "hair-dryer" test method, it outperformed HP's original design in terms of temperature drift.It is a drop-in replacement but it requires the original transformer/capacitor/inductorAC supply to be replaced with a switch-mode version AND filtering bringing the input voltagedown to 24VDC.Check out KO4BB's 5065 folder.