HP 5316A Teardown and Frequency Standard - Page 1
Forum section: electronics / testgear

author: amc184
author_rank: Regular Contributor
timestamp: October 17, 2014, 05:14:31 am
content: I bought this HP 5316A from eBay, and it was another classic eBay purchase. It was sold as powering on but otherwise untested. When I got it, it partially worked but threw fault codes and was really, really sticky and brown. Maybe it was used by a smoker? It cleaned up nicely and the internals were pristine, so for USD36 it was a great deal.I replaced the electrolytics and tantalums and the counter worked correctly. The only other thing that bothered me about it was that it was just the base model with a basic crystal as the frequency standard. There were two frequency standard options for the 5316A; 001 (a TCXO) and 004 (an OCXO). Looking at the service manual, these options were pretty simple, mainly just a regulator to bring the 8 to 10VDC standby supply down to whatever the TCXO or OCXO needs (5VDC in both cases). I designed a small PCB with a regulator and a Morion MV85A OCXO. These are available cheaply on eBay and require a 5VDC supply. Most require a 12VDC supply, and I really didn't want to have to have a step up supply, especially as the oven draws a fair bit of current on startup.The PCB works well, it mounts on standoffs right where the original oscillator card sits. The calibration pot lines up okay with the hole in the rear panel, now I just have to figure out how I'm going to calibrate it ....I have some spare PCBs as well, if you have a 5316A and want one PM me. I think it should work in a 5316B as well.

author: David Hess
author_rank: Super Contributor
timestamp: October 17, 2014, 06:03:50 am
content: These are fabulous counters. I have an HP 5315A with the TCXO option which can be seen edge on in the photo below.I calibrated mine using the 5 Hz timing output on my GPS and a long gate time.

author: psykok
author_rank: Frequent Contributor
timestamp: October 17, 2014, 06:40:08 am
content: Hi,Great work, I have the same counter but with TCXO option.Alex

author: daqq
author_rank: Super Contributor
timestamp: October 17, 2014, 07:18:40 am
content: Good job! Thanks for the peek inside!

author: nixxon
author_rank: Frequent Contributor
timestamp: November 11, 2014, 11:24:53 pm
content: I have agreed with a dude to pick up a HP 5315A with option 003 (1 GHz Channel C).I am thinking about retrofitting a OCXO. I have noticed that (i.e. reading the last page here:https://www.valuetronics.com/Manuals/HP_5315A_HP_5316A.pdf) that the option 004 "High Stability OVEN Time Base" differs between the 5315A and the 5315B/5316A.Do you think that the DIY option 004 equivalent that fits the 5315B/5316A will fit the 5315A anyway?

author: amc184
author_rank: Regular Contributor
timestamp: November 12, 2014, 06:16:59 am
content: It looks to me like the form factor of the plug in frequency standard modules is the same for both the 5315 and 5316. The problem with using the PCB I made in the 5316 is the black plastic pillar to the left of the two holes the PCB mounts to. This will interfere with the top left corner of the PCB, where 'REV B1' is written. You could just file that corner off, though you might have to route the RF output trace if you cut that far into the PCB.

author: nixxon
author_rank: Frequent Contributor
timestamp: November 12, 2014, 09:21:23 am
content: Maybe option 004 for the plastic cased 5315A is less power hungry than option 004 for the other two stackable/rackable, metal chassis models (5315B and 5316A), because the 5315A may be run on batteries. For some reason, option 004 for the 5315A originally cost $460, whereas option 004 for the stackable/rackable models cost significantly more, $605.amc184: Is the size and shape of your DIY option 004 PCB identical to that of the standard A7 assembly that was replaced in the 5316A?(in the 5315A, option 004 replaces the standard A13 oscillator assembly)

author: nixxon
author_rank: Frequent Contributor
timestamp: November 13, 2014, 02:43:51 pm
content: Quote from: amc184 on November 12, 2014, 06:16:59 amI just picked up my 5315A. It looks very nice and clean on the inside. The standard oscillator circuit board (assembly) is standing perpendicular to the main board on it's long edge. The oscillator circuit board is ~75 mm long and ~31 mm tall. There are 6 pins connected to the main board. To access the frequency adjust screws, the instrument top cover must be removed.Do you think the "HP 5316A OPTION 004 EQUIVALENT" board will work with the 5315A as well? (With some fastening mods).

author: amc184
author_rank: Regular Contributor
timestamp: November 13, 2014, 10:22:57 pm
content: The oscillator boards in the 5315 and 5316 are the same form factor, and look to be the same circuit. The component layout is a bit different, allowing for closed case calibration in the 5316. However, the replacement module I've made is not quite the same as the original board. While the original PCB sits vertically, mine sits horizontally. I dismantled my 5316A to get some more shots, this time with the side rail removed for clarity.Original clock module:My replacement OCXO module:The component side of the original 5316A module:The main reason I chose to change the orientation like that was because I have no idea where to get those little rivets o angle brackets on the original module. Even if I could, they're not really suitable for the greater weight of the OCXO; the original option 004 PCB only held the voltage regulator, the OCXO was mounted separately on a bracket. My module mounts onto two standoffs, which screw into the original threaded holes in the PCB.So to amble back around to your question, my answer from yesterday hasn't changed. If you want to use this board, you'll need to modify it to accommodate the large plastic pillar in the 5315 (the one underneath the text '~31mm' in the second picture of your last post).

author: amc184
author_rank: Regular Contributor
timestamp: November 13, 2014, 11:00:50 pm
content: I've had a look at the HP 5315A/B service manual, and it looks like the 6 pin header's pinout might be different to a 5316A/B. However, that same manual also suggests that a 5315 would have the basic oscillator built into the mainboard, and a plug in module would only be used for the options, so it clearly doesn't match your 5315A. Here's the pinout for the 5316A and my module:1) VCC (roughly 10VDC, unregulated)2) RF3) GND4) NC5) NC6) VCC (roughly 10VDC, unregulated)It'd be good if you could have a look at your 5315A and determine its pinout.

author: nixxon
author_rank: Frequent Contributor
timestamp: November 13, 2014, 11:18:46 pm
content: Thank you for the information and pictures. Very interesting. There are a few different versions of the 5315A/B manual, corresponding to different serial prefixes. The manual covering my unit has the 2120A serial prefix and is printed in 1981. I will figure out the pins in my unit, to compare with the 5316 pinout.For some reason, the 5315A/B manuals I have found are missing the service section (VIII).The 5316A manual does however include Section VIII with Service info and the schematics of the OEM OCXO as well.

author: nixxon
author_rank: Frequent Contributor
timestamp: November 14, 2014, 08:03:08 pm
content: Quote from: amc184 on November 13, 2014, 11:00:50 pmThe pinout of the 5315A is the same as the 5316A (pin 1 closest to the corner):1) ~+8.8 V (with 600 mV sawtooth ripple)2) 10 MHz (Fluke 87: ~+1.44V)3) GND4) +5.00 V5) NC (+0.001V)6) ~+ 9.5VEnclosed is a screenshot of the signal on pin 2. My Rigol 1102 (1052 with mod) oscillator is in sync with the 5315A oscillator, showing 10.0000 MHz and sometimes 9.99999 MHz). The Rigol Vrms Offset is identical to that of the Fluke 87: +1.44V.I now wish I had an "HP 5316A OPTION 004 EQUIVALENT" PCB to populate with, along other components, my recent eBay order of a "MORION MV85A OCXO"...

author: amc184
author_rank: Regular Contributor
timestamp: November 14, 2014, 09:10:43 pm
content: It looks like the PCB will work. The pinout for the earlier 5315 was:1) NC2) RF3) GND4) VCC (5V regulated)5) NC6) NCSo it looks like your later 5315 is designed to allow the use of either type of module. I'll PM you about getting a PCB shipped to you. I've also attached the schematic, design files and gerber. Anyone should feel free to use them to make their own PCBs, or modify them to suit their own counter. They're made with DipTrace, the type numbers in the bill of materials are element14 part numbers.

author: nixxon
author_rank: Frequent Contributor
timestamp: November 14, 2014, 10:00:57 pm
content: That is very kind of you. Thank you very muchIt seems that my Siglent SDG1020 is the one instrument of mine that is out of sync (18 ppm). In that regard, I am looking forward to receiving a $25 "1PCS Vanguard TCXO 0.1ppm 25.000MHz Ultra precision Golden Oscillator AQ" that I ordered the other day from along1986090 on eBay. Both this and the other oscillator (OCXO for the HP) hopefully arrive in time for the Christmas holidays.Some good reading on "Understanding Frequency Counter Specifications" by HP:http://www.leapsecond.com/pdf/an200-4.pdf

author: mweymarn
author_rank: Contributor
timestamp: November 16, 2014, 02:40:56 pm
content: amc184 kindly sent me one of his PCBs. I used it to upgrade the timebase of my HP 5316B. This counter has a slightly different mechanical layout, nevertheless the PCB fits perfectly as can be seen in the photo.Unified standoffs and spacers are hard to come by in Europe. Luckily standard M3 10mm standoffs fit perfectly. Although a little tight the M3 screws can be run through the 6-32 nuts which are riveted to the counter's main board.The OCXO calibrates very well and is extremely stable. An amazing upgrade, especially compared to the standard timebase!

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 16, 2014, 05:36:24 pm
content: Odd, mine looks like this

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 16, 2014, 05:40:57 pm
content: Quote from: Alex Eisenhut on November 16, 2014, 05:36:24 pmBecause it has the C input option.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 16, 2014, 06:20:05 pm
content: Quote from: PA0PBZ on November 16, 2014, 05:40:57 pmYeah but I mean graphically, even the HP logo isn't the same.

author: amc184
author_rank: Regular Contributor
timestamp: November 17, 2014, 05:22:00 am
content: Yeah, yours is a little bit older, maybe 1983. Mine is around 1985 vintage.Thanks for the picture mweymarn, it looks really good, nice clean build. I checked out the service manual as best I could when I designed the PCB to try to make sure it would fit both types of 5316, I'm glad it worked.

author: nixxon
author_rank: Frequent Contributor
timestamp: November 18, 2014, 01:17:37 pm
content: Quote from: amc184 on November 14, 2014, 09:10:43 pmThank you for attaching the schematics, layout files and gerber. They gave me a reason to download DipTrace, simply to be able to read all the files. It looks very impressive. Maybe, the layout files will make a good starting point to learn a little about DipTrace as well.When I look at the schematics ("004 B1.pdf"), I notice that there are 2 capacitors (C101 and C102) in parallel between +10 VCC (pins 1+6) and GND (pin3). C101 is huge, 330 uF, compared to C102, 100 nF. They both add up to a capacitance of 330uF + 0.1uF = 330.1uF.My noob guess is that C101 is there to reduce the ~600mVpp ripple of the VCC.My noob question is: What is the purpose of C102?(I notice a similar thing between the +5V output of U101 (LM1085, powering the OCXO) and GND as well. One huge, 330uF capacitor, C105, in parallel with multiple tiny capacitors, C104, C106 and C107. They all add up to 330.201uF. What is the purpose of adding 0.201uF to 330uF?)

author: SharpEars
author_rank: Unknown
timestamp: November 18, 2014, 02:25:36 pm
content: Perhaps a stupid question but:If you already have a two channel oscilloscope with a built in frequency counter as one of its many stat/math functions, is there any point in getting a frequency counter that covers the same range as the scope?In other words, why are all of you getting and/or in possession of these if modern scopes give you frequency counts along with waveforms?

author: nfmax
author_rank: Super Contributor
timestamp: November 18, 2014, 02:51:02 pm
content: Here's a few reasons!My counter goes up to 3GHz, but my fastest scope is only 200MHzThe counter has interpolation for more digits/second resolutionWith a universal counter, you can measure things like the number of pulses on an interrupt line that occurred while /RESET was low

author: amc184
author_rank: Regular Contributor
timestamp: November 18, 2014, 06:38:19 pm
content: Nixxon; the small capacitors are for decoupling.SharpEars; A few reasons. I mainly leave this counter connected to the sync input of my signal generator (HP 3312A with no frequency display). Sometimes I may be viewing something other than an amplifiers output, such as its supply rails, yet I still want to know the frequency of what I'm feeding it. Also for accuracy. I can't discipline my 'scope to a 10MHz reference.Aside from those concerns, a counter is cheap. I think the 5316A cost me about USD30, maybe another USD20 for the clock module. You only need it to be useful now and again to justify that sort of cost.

author: David Hess
author_rank: Super Contributor
timestamp: November 18, 2014, 07:00:21 pm
content: Quote from: amc184 on November 18, 2014, 06:38:19 pmThe HP5316A is also a reciprocal counter so it returns a constant number of digits at a given gate time producing high resolution at low input frequencies. On analog oscilloscopes which support gated measurements, reciprocal counters are common but it is not clear if that is the case with DSOs.DSOs with long record lengthsshouldbe able to equal the performance of a good timer/counter without additional hardware support but I have yet to see this happen. They all seem to be mediocre at best.

author: nixxon
author_rank: Frequent Contributor
timestamp: November 19, 2014, 12:44:59 pm
content: Quote from: amc184 on November 18, 2014, 06:38:19 pmThank you for making that clear.Is there any reason why the 5V OCXO can not be powered directly by the existing +5.00V supply (pin 4)?To me it seems that the instruments's +5.00V supply (pin 4) is powered by the unregulated +7,5V that is also present on pins 1 and 6.The Morion MV85 OCXO has a peak power consumption of <600 mA during warm-up.

author: David Hess
author_rank: Super Contributor
timestamp: November 19, 2014, 02:28:43 pm
content: Quote from: nixxon on November 19, 2014, 12:44:59 pmThe way it was originally designed, the XO and TCXO use the +5 volt logic supply but the OCXO instead has a discrete low dropout regulator to provide +5.0 volts from the +7.5 volt unregulated supply. Offhand I can think of two reasons HP did it this way:This distributes the power dissipation across two regulators and avoids overloading the discrete +5 volt logic regulator. Doing it this way would be less expensive if a majority of the counters did not include the OCXO option because the +5 volt logic regulator would not need to be as powerful.Noise and drift on the logic supply may compromise the OCXO performance.I probably would have used a separate regulator even for the XO and TCXO.

author: nfmax
author_rank: Super Contributor
timestamp: November 19, 2014, 02:53:45 pm
content: The OCXO is powered from the permanently on 7.5V supply, so it is kept running in standby. Crystal oscillator drift is approximately proportional to the square root of time, so the longer it has been powered on the (relatively) more stable it gets.

author: David Hess
author_rank: Super Contributor
timestamp: November 19, 2014, 03:18:16 pm
content: That is an even better reason that I should have remembered. My best counter does the same thing even with the TCXO.

author: amc184
author_rank: Regular Contributor
timestamp: November 20, 2014, 05:29:02 am
content: Yeah, you guys have got it. The two main reasons are:- To keep the OCXO powered and up to temperature at all times so the counter can be turned on and used without delay. An SC cut crystal won't even put out the right frequency when it's cold, let alone stability.- To make sure the 5V rail isn't overloaded. An OCXO draws a lot of current. The MV85 is actually quite frugal, drawing up to 600mA on start up and 200mA steady state, many are much worse. You can't assume a regulated rail can provide this much extra current.Besides all of that though, when I designed the board I just wanted to duplicate the function of the original as closely as possible with more modern parts that are easily available now. I didn't put much time and thought into changing anything, this was just a quick side project. I mainly do audio.

author: HiTech
author_rank: Regular Contributor
timestamp: November 20, 2014, 06:45:52 pm
content: Very nice work/detail on your mod -- AMC184.

author: JoeD
author_rank: Contributor
timestamp: November 29, 2014, 12:21:32 pm
content: Received a board from amc184 and have built and fitted to my 5316a. Working well, have used rubidium reference to set it up and it's very stable. The Morion OXCOs are absolutely rock steady and the fourth picture shows the oscillator output reading on a Racal 1998 in overflow mode. That's 10.000000010 MHz ie 10 parts in a billion out...Nice board Anton, thanks very muchJoeD

author: nixxon
author_rank: Frequent Contributor
timestamp: December 16, 2014, 12:49:40 pm
content: Quote from: JoeD on November 29, 2014, 12:21:32 pmVery nice results and heat-sink. Did you do the math to calculate the minimum size of the heatsink for the LM1085? With a Vin to the LM1085 of ~9V and a 5V output, the voltage difference is 4V. Multiply that with the < 600 mA power consumption of the OCXO, and it seems that the LM1085's output section must dissipate some 2.4W during OCXO warm up. After a couple of minutes the power consumption of the OCXO is <200mA, so the LM1085's output section needs to dissipate up to 800mW. In addition to the output dissipation, the LM1085 also has to dissipate the power from the control section. This is possibly negligable compared to the power dissipation?The next step would be to calculate the thermal resistance between Junction and Ambient. I guess any value < 30 deg C/W would be safe...

author: nixxon
author_rank: Frequent Contributor
timestamp: December 23, 2014, 08:33:59 am
content: I forgot to order a heatsink for the LM1085 voltage regulator when I ordered all the parts for the OCXO assembly. I found a disposable serving tray that was made by thin (~0.3 - 0.4mm) Aluminium and used scissors to cut out two identical shapes that could be folded into a suitable heatsink.Then I could finally finish the last part of OCXO assembly by installing the LM1085. Little did I know that the OCXO would fail miserably...

author: nixxon
author_rank: Frequent Contributor
timestamp: December 23, 2014, 12:53:01 pm
content: Quote from: nixxon on December 23, 2014, 08:33:59 amWhen I slowly increased the voltage to the 004 equivalent assembly, I noticed that the power supply seemed to be faulty. The voltage didn't go up as much as expected. But the amps did, rising to ~3A. And I could tell that the heatsink I had made was getting really warm. So I measured the resistance between the assembly voltage input pin and GND, and it was above 100 Ohms and not very low/shorted. However capacitor C105 was shorted. And so were the other capacitors between the 5V rail (LM1085 OUT) and GND, C104, C106 and C107. Then I looked at the LM1085 datasheet and noticed that the mounting tab, where the 3mm mounting bolt goes through, was not GND, but voltage output. Therefore I removed the bolt going through the LM1085, the heatsink and the PCB. I was not convinced this would make a difference, as the PCB ground plane was not exposed around the hole for the LM1085 on either side. And everyone else that have built his thing have just put a metal bolt straight through. Nevertheless, the OCXO assembly was now reacting very differently as I applied power to it. I could see the 10 MHz output on the scope as well, as I noticed that the current, that this time had started out at ~0.6A, was decreasing. Success!With the assembly running, I reinserted the 3mm bolt, and all was OK initially. I had to tightened the nut a little bit before the output of the OCXO was affected. Maybe the designer, amc184, or someone else that can read the gerber design files in reply #12 in this thread can figure out if the bolt hole is drilled through the copper ground plane of the PCB. Maybe it barely makes contact with the ground plane edge in the hole as the nut is tightened?Now I only have to find a way to fasten the LM1085 to the rest of the assembly. It is odd that everyone else that have done this job before me seem to have had success by simply putting a plain bolt straight through, without electrically insulating it.By the way: the 20 turn trimpot is a very good design choice (made byamc184) to adjust the frequency output of the OCXO. No need to have the right tongue angle, as one full turn makes less than 0.1 ppm (1Hz) change.

author: nixxon
author_rank: Frequent Contributor
timestamp: February 20, 2015, 10:43:11 am
content: 5316A option 004 equivalent install (in 5315A) update:To avoid the problem with shorting the TO-220 style voltage regulator to ground, I replaced the metal screw with a nylon screw. I ordered a bag of pretty nicely finishedM3 nylon screwsfrom dealextreme.com. I orded rather long screws and trim length as needed with side cutters.At the same time, I ordered a bag ofM3 nylon standoffsfor the 004 equivalent board. The nylon threads will fasten ok and not damage the 6-32 nuts which are riveted to the counter's main board. The standoffs were too long, so I had to trim the lenght.Just like amc184 suggested previously, I had to modify the 004 equivalent board (I used a Dremel sanding drum) to accommodate the large plastic pillar in the 5315A. Because of the mod, I also had to route the RF output trace with a (bodge) wire, as you can see on the picture.I calibrated the OCXO just before Christmas, and it is still spot on, as seen in the picture. In the picture, the most significant digit ("1") is missing due to overflow mode. The display should be read as 1.00000000 Hz. (I used a Rubidium Standard FE-5680B with 1 pps output and long gate time to calibrate and check calibration).Thanks to amc183 for making this mod possible.I also checked how accurate my Siglent SDG1020 signal generator is with a Vanguard 0.1 ppm TCXO installed. It is exactly 0.1 ppm off. A 10 MHz output signal is measured to 9.9999990 MHz on the 5315A. (This is 180 times more accurate than the standard SDG1020 crystal that was 18 ppm off).

author: nixxon
author_rank: Frequent Contributor
timestamp: February 20, 2015, 01:22:05 pm
content: Quote from: JoeD on November 29, 2014, 12:21:32 pmIf I have got it right, the Racal reading of10.000000010 MHzis only 1 part in a billion out (0.01 Hz or 10 mHz off).A 3.6° (1/100) turn on the 20-turn pot, roughly, should make it 10 times more accurate. That is unless the OCXO drifts a lot at this level ofaccuracyresolution.

author: schopi68
author_rank: Regular Contributor
timestamp: March 29, 2015, 03:06:42 pm
content: Ugh.I've just finished my OCXO-Replacement for the 5316B, built some spare devices and now i found this thread. Hmmm... maybe i should have had a look into this forum during the last months.

author: nixxon
author_rank: Frequent Contributor
timestamp: March 31, 2015, 04:44:16 pm
content: Quote from: schopi68 on March 29, 2015, 03:06:42 pmDid you design your own OCXO "option 004 equivalent"? How did you solve it? Any pictures?

author: schopi68
author_rank: Regular Contributor
timestamp: March 31, 2015, 09:01:28 pm
content: Quote from: nixxon on March 31, 2015, 04:44:16 pmyes, i did my own design, starting last november. Currently i am in the progress of writing down the most important things on my web page to document everything as i have the intention to make the device also available for other interested hams and electronic enthusiasts.In the meantime the first four devices will get a "one month burn in" to ensure that the old MV85 OCXOs i used (in three devices) are still reliable and to give the new AXTAL OCXO in the fourth device some pre-aging before doing the final calibration with my GPS-based reference.I have some pictures on mywebsite(Thisis the overall project page which i am still updating).This is an image of my device side by side to the original hp 05316-60008 oscillator:

author: xrunner
author_rank: Super Contributor
timestamp: April 08, 2015, 05:34:23 pm
content: No need for a new thread - just got this in from an Ebay seller. Got a replacement knob from another seller too. Haven't turned it on yet.

author: schopi68
author_rank: Regular Contributor
timestamp: April 08, 2015, 08:22:33 pm
content: Quote from: xrunner on April 08, 2015, 05:34:23 pmseems to be in a good condition. What is the serial number (to get the production date)?

author: xrunner
author_rank: Super Contributor
timestamp: April 08, 2015, 09:26:15 pm
content: Quote from: schopi68 on April 08, 2015, 08:22:33 pm2204A09671Can you get the date?

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 08, 2015, 09:33:23 pm
content: Let me throw in a guess: Week 4 1982, made in USA?

author: schopi68
author_rank: Regular Contributor
timestamp: April 08, 2015, 09:48:28 pm
content: Quote from: xrunner on April 08, 2015, 09:26:15 pmyes, that's possible. But i have to correct myself a little bit: the date encoded in the serial number is the date of the last design change. In most of the cases this corresponds to the real production date within a rage of 1 or 2 years.The serial number is built of two parts:The serial number prefix contains the date of the design change and the country of origin.The first two digits indicate the year (beginning with 1960 = 00)The second two digits indicate the week.The Letter designates to A=USA G=Germany J=Japan U=United KingdomThe third part is the 5-digit serial number starting with 00101So your unit was built after week 4 in 1982 in America.To get a more exact date you should have a look on the datecode of the parts in the device.

author: xrunner
author_rank: Super Contributor
timestamp: April 08, 2015, 10:37:36 pm
content: Quote from: schopi68 on April 08, 2015, 09:48:28 pmThanks for that info.Since I'm doing a cosmetic restore, I'll post a few more pics that I didn't see in the thread. I have turned it on and it's working properly. I did find the microcomputer IC was not seated properly in it's socket, so fixed that. Also interesting is the LED display ICs are all in sockets, as opposed to the two other HP DMMs of that era I have, which are all soldered in. Noted too is the ability to slide the plexiglass panel out from the aluminum front panel. Also found was the B Channel Level / Sens pot had a leg worked loose from the solder, so needs to be touched up.

author: amc184
author_rank: Regular Contributor
timestamp: April 09, 2015, 04:33:38 am
content: QuoteYour design looks great schopi68. It's funny how close the two independent designs came out. I chose to make mine horizontal because I thought it would be hard to get the right angle brakets that the original used. I like the unusual standoffs you've used, are they an off the shelf part?QuoteThat's not quite how the HP serial numbers work. The first two digital are years since 1960, but it's the year of the last design revision. That's why that units serial starts with 22, meaning 1982, but many of the ICs are date coded 1983. It was a version they started producing in 1982, but this unit was from 1983 or later.

author: schopi68
author_rank: Regular Contributor
timestamp: April 09, 2015, 09:35:15 am
content: Quote from: amc184 on April 09, 2015, 04:33:38 amYes, tt is quite interesting to see how many OCXO-Boards for these old HP counters are currently on their way. Maybe now the time is ripe for this kind of boards. At the beginning of the year i planned to design a board for my HP 5334B too after finishing the 5316-pcb. But i am no longer sure if somebody else will do this job faster.The standoffs are off the shelf parts, which i had to modify slightly. Normally they are mounted in a 90° direction, with the flattened side to the pcb. There has been a threaded hole in this side which i had to drill out. With this modification (and somewhat longer screws) it fits perfectly to the counters main board.Quote from: amc184 on April 09, 2015, 04:33:38 amPleas have a second look to the description i made - i think i already wrote this.

author: schopi68
author_rank: Regular Contributor
timestamp: April 09, 2015, 09:42:20 am
content: Quote from: xrunner on April 08, 2015, 10:37:36 pmGreat to see that it's still working!When the device is still open (and maybe reassembled again)... I'd like to know if my pcb could fit into this device or if i have to find another heatsink. Could you measure the distance from the oscillator pcb's surface to the case?

author: xrunner
author_rank: Super Contributor
timestamp: April 09, 2015, 11:36:16 am
content: Quote from: schopi68 on April 09, 2015, 09:42:20 amYes I will do that today.Also have a question about the PS filter caps, I'll post a pic about that as well.

author: xrunner
author_rank: Super Contributor
timestamp: April 09, 2015, 06:30:27 pm
content: The distance from main board to the top is 33 mm. Distance to the side of case is 28 mm (the case is curved so this is the smallest distance.Have a question also. There are two main filter caps. Both of them have one negative lead and two positive leads. The 4700 uF axial has the two positive leads going to two two different traces, and the 2200 uF radial has the two positive leads going to a single trace (but on the schematic it does not indicate this). If I might want to replace these going forward, what is the designation to specify in the parts search engine of places like Mouser? I am not familiar with caps like these with two positive leads that aren't identified on the case as such. Does that means their are two complete capacitors inside them even though it does not specifically say so on the outside?

author: schopi68
author_rank: Regular Contributor
timestamp: April 10, 2015, 07:54:33 am
content: Quote from: xrunner on April 09, 2015, 06:30:27 pmgreat to hear that, the heat sink i use for the power regulator has a height of 25 mm. So my ocxo could also be used (but would need to replace the fuse on it by a resistor to keep power on-current under control - otherwise the cap on the counters main board would charge the cap on my board with a uncontrolled high current each time the power switch is depressed - but it looks as if there is no continous power available, so maybe an ocxo isn't the best choice for this device).Quote from: xrunner on April 09, 2015, 06:30:27 pmIn most cases the third pin is just for mechanical stabilization of the cap (the one placed on the metal-plated side). Without it, the cap would move during soldering or fall of during vibrational tests. Interesting to see that even this stuff had a Patent some time ago:http://www.google.com/patents/US4763227So if you need to replace the cap with a more modern one it wouldn't be a problem to use a 2-pin cap. If this is still very big in size it could easily be glued with a small amount of hot glue to get it mechanical stable.

author: xrunner
author_rank: Super Contributor
timestamp: April 10, 2015, 12:09:27 pm
content: Quote from: schopi68 on April 10, 2015, 07:54:33 amAh OK good to know that.Was doing some testing yesterday, and found that even though the unit is spec'ed to 100 MHz it will go into the 2 meter ham bands very well, as shown in the pic (last digits were changing so they look messy). Transmitting on 144.000 MHz.Also hooked a small antenna to the Osc. test point and was able to zero-beat the internal 10 MHz ref to WWV on same freq. using my ham/shortwave receiver, per the procedure used by W2AEW Was just a touch off but very close. If anyone wants a good freq, counter for the ranges this covers it's a very good piece of gear!

author: schopi68
author_rank: Regular Contributor
timestamp: April 10, 2015, 12:31:20 pm
content: yes, these units are scaling up to a lot more than specified. From it's bigger brother, the 5316B i know that it scales up to 180 MHz (and more) - this is likely the same for the 5315a (input circuit is identical for both units). Only the input sensitivity may be completely out of spec.

author: cpu_bach
author_rank: Newbie
timestamp: April 08, 2016, 08:39:37 am
content: amc184 kindly sent me his PCB for my HP-5316A. I had to mount OCXO slightly above the PCB surface, because original OCXO's leads were too short to directly solder on the board. I confirmed stable operation of the assembled module. I am waiting for the delivery of standoffs which are not popular in ISO standard country.Thanks a lot, amc184!

author: Smith
author_rank: Frequent Contributor
timestamp: April 08, 2016, 03:17:11 pm
content: I replaced mine with a stable high quality TCXO, works like a charm! I just used a standard header, some test PCB and 2 stand-offs to create my own PCB. Next time its open I'll take some pictures (Of course I forgot to).It's a verry nice uit to work with. Lots of options for measurements, nice display. Only thing I dislike is it's enormous length. Oh well, gues it fits my HP 8116A function generator

author: cpu_bach
author_rank: Newbie
timestamp: April 11, 2016, 02:49:57 pm
content: After receiving the stand-offs, I mounted OCXO board in my HP5316A. IC heatsink comes very close to HP-IB board, but there is a clearance.

author: amc184
author_rank: Regular Contributor
timestamp: April 13, 2016, 05:13:01 am
content: Looks good, shame your OCXO came with such short legs. I would have used a smaller heatsink for U101, but if it fits it works. I'm in a metric country, so I would have rather used metric standoffs as well, but it's driven by the imperial threaded inserts in the mainboard. I think at least one person used a smaller diameter metric standoff with a nut, using the inserts like a plain hole.And yeah, for a half width unit it'sreallydeep.

author: wmactor
author_rank: Newbie
timestamp: July 21, 2016, 03:40:08 pm
content: Quote from: amc184 on October 17, 2014, 05:14:31 am---------Thanks for sending me one of your boards, amc184 - much appreciated! I finally received the MV-85 OCXO module from China, and assembled the circuit. It fit perfectly into my 5316B, calibrated well, and is running very stable.Here are a few pictures...The first photo shows the assembled board, and the second is a shot of it installed in my 5316B. The third is an overall view of the 5316B with the module installed, running a self test - the original HP oscillator is on the table to the left of the unit. The fourth photo is my 3336C generator (with its original HP OCXO installed) sending a signal of 59,932,416.9 Hz to the 5316B, and the counter displaying it accurately!Thanks again, Anton, for all of your effort on this project!Regards,WayneToronto, Canada

author: kj7e
author_rank: Frequent Contributor
timestamp: February 16, 2018, 11:49:10 pm
content: Thought I would add some photos of a recent addition, although its the B version. I found a clean 5316B with option 003 (1GHz Channel C) and a parts only 5316B with option 004 (High Stability OCTX). The Oven and voltage regulator in the parts unit worked perfectly so they where transplanted. Even though the original blue Sprague power supply caps seemed okay, I replaced then with some slightly higher capacity Nichicon caps, Digikey part numbers below;1 1 493-1312-ND UVZ1E223MRD CAP ALUM 22000UF 20% 25V RADIAL 0 4.25000 $4.252 1 493-1326-ND UVZ1V682MRD CAP ALUM 6800UF 20% 35V RADIAL 0 3.14000 $3.14Did they really have to make it so long?Option 004;Power supply caps replaced;Input and option 003 board;

author: xrunner
author_rank: Super Contributor
timestamp: February 17, 2018, 02:09:52 am
content: Nice 5316B. I got one last year and it's a great unit.

author: Robby
author_rank: Newbie
timestamp: March 15, 2019, 09:30:56 am
content: While on the subject, what of the availability of any more of these OCXO boards?Got a 5316a in need of an upgrade.Please shoot me a message or a post - please?Thanks!

author: Luthor2k
author_rank: Newbie
timestamp: April 07, 2020, 05:02:17 am
content: PCBs incoming. Am fixing up my 5316B and have just ordered five of amc184's Morion MV103a boards made up by PCBWay. The remaining four are up for grabs if anyone is interested. Will post when I've got them on hand and tested.Cheers!

author: Luthor2k
author_rank: Newbie
timestamp: May 03, 2020, 08:50:57 pm
content: PCBs arrived and installed, works great. Thanks amc184! I've got four boards spare now if anyone wants one.

author: pinpassion
author_rank: Contributor
timestamp: June 09, 2020, 09:17:24 am
content: Hi,I'm new to EEVBlog and I'm trying to purchase one of the spare OCXO boards you have. I got the board files from Anton, and will have them made if i need to, but I would prefer to purchase one of your spares if i can. I sent a previous message to you, but did not hear back. i don't know if you received it.Thanks for your consideration.Mike

author: Luthor2k
author_rank: Newbie
timestamp: June 18, 2020, 07:35:04 pm
content: I am shipping a pcb out today, still have three up for grabs though no more trim pots on hand.

author: Luthor2k
author_rank: Newbie
timestamp: June 19, 2020, 12:45:38 am
content: A second PCB is going out tomorrow. There are two remaining and parts minus the trim pot.

author: Luthor2k
author_rank: Newbie
timestamp: June 19, 2020, 10:19:45 pm
content: Only two boards remaining now!

author: Luthor2k
author_rank: Newbie
timestamp: June 22, 2020, 02:21:33 am
content: I received a questing from someone about the TCXO board install in my counter and thought I'd repost here for all:"I have a question about mounting and using the OXCO board in the HP 5316B. Many of the users of the board were using them in a 5316A. There are significant differences in that earlier model. I know you have a "B" model too, and your posted photo is in that unit. Apparently the "A" model had an external factory oscillator, so it was a matter of removing that board, and plugging in the replacement. In my unit, (and I assume yours) there is a crystal oscillator soldered on to the main board that supplies the 10MHZ reference sinewave. I don't know if the replacement board will mount over that factory crystal, or if I need to desolder it from the main board prior to installing the new board in the socket. I'm not sure if the firmware detects the oscillator and switches to it, ignoring the on board oscillator?My on board crystal actually has a zip tie holding it down tightly to the main board , in addition to the fact it is soldered to the PC board. Did you desolder your factory crystal prior to installing the OXCO board, or is yours mounted over the on board crystal?"My answer to this is; nope, nothing desoldered! I did however remove an oscillator board from my counter. A photo of the board I removed is attached. During the process I also replaced the two large electrolytic power supply caps. Nothing else was changed.

author: pinpassion
author_rank: Contributor
timestamp: June 22, 2020, 02:30:52 pm
content: Hi Gang,There is something I wanted to clarify on my particular HP 5316B counter. I think I may have a later unit then some or all of the posters so far wishing to add a OCXO oscillator board to their unit for added accuracy and stability. My "B" model does not have a daughter board as a factory internal oscillator. It has an on-board crystal soldered and secured to the main board with a zip tie. To the best of my knowledge, this is a factory installed crystal, and my unit never had an oscillator as an external board to the main unit. I am including pictures of this crystal on the main unit in both top and bottom photos. Seeing is believing..My unit serial number is 3005A07XXX.I am wondering if I need to desolder this crystal to remove the 10MHZ signal, or if the firmware will recognize the external board plugged into the 6 pin connector and switch to it's signal for calibration? The crystal is mounted directly over one of the mounting holes for the daughter board, but i could use an alternate mounting arrangement if needed for the replacement OCXO. I will remove the crystal if i have to, but would prefer to leave it there if I can.Also, if anyone has the feet that were mounted to the cabinet bottom and are willing to part with them, please let me know. My unit was rack mounted, so they are missing. I especially would like the front feet that had the swing down bail for elevating the front off the bench.Thanks,Mike

author: Luthor2k
author_rank: Newbie
timestamp: June 24, 2020, 05:25:45 am
content: Hey Pinpassion, attached is a photo of my counter, no 10mhz crystal to be found. Perhaps chase the trace? Those 4-pin XOs have low Z outputs IIRC...

author: amc184
author_rank: Regular Contributor
timestamp: June 24, 2020, 10:59:45 am
content: Hi Mike,That's interesting, it seems your unit is different to the others. Looking at Luthor's unit, it looks like the large DIP packaged crystal oscillator might be socketed using individual pin receptacles. This would also explain why it is zip tied down. It should be easy to remove (no desoldering needed), which is good because I think you'll need to.I've attached this section of the circuit below. J2 at the left is the connector that you'll plug the OCXO board into. Pin 2 is the output of that board. Y1 is the crystal oscillator installed in your mainboard, and after the buffer this joins into the same net used by the OCXO output (which I've highlighted yellow). You wouldn't want both clock sources driving the same net, so Y1 must go.Besides that, I think you need to use the hole right underneath Y1 to mount the OCXO board, right?

author: pinpassion
author_rank: Contributor
timestamp: June 24, 2020, 12:01:14 pm
content: Hi Luthor2K,Thanks for removing your board and taking a picture. Very interesting! You have the circuitry for the on-board crystal (Y1) but not the crystal! It's place on the mainboard can be seen, so the pads are there, and the same holes that are on my board where the zip tie is holding it down. You even have the oscillator adjust trimpot. What I think may explain this is when they introduced the "B" counter model, HP wanted to exhaust the supply of the external boards that were used on the "A" model, and when that was done, they soldered the crystal to the main board to replace the daughter board entirely. This must have been the plan when the PC board was manufactured and that explains the pads and circuitry.I downloaded a service manual scan online for the 5316B, and had a look at the schematic. The on-board crystal is shown. Examining the schematic, it looks like I will have to desolder my crystal to take advantage of the OCXO board before I install it in J2 on the mainboard. If I didn't, both 10MHZ signals would be injected. There are ways around doing it, like lifting pin 2 from the OXCO board and running that into the external input and keeping the rear panel switch in the external position, but I think I will just bite the bullet and remove the crystal. If I did wire the OCXO into the external input, the one interesting benefit is i would be able to switch back and forth to the on-board crystal and the OCXO board easily to compare both references..Nah...I know the OCXO board is going to be a lot better.Thanks for taking the picture. It helped me to understand the whole external oscillator issue.Mike

author: pinpassion
author_rank: Contributor
timestamp: June 24, 2020, 12:16:46 pm
content: Hi AMC184,Wow..Our posts crossed!! You came to the same conclusions as me! I was hoping the crystal was socketed on the mainboard, but as you can see in the board bottom photo, it is soldered...OR, is that the pins to the socket that are soldered...? I don't know!! I am hoping it is a socket!! We will see after I remove the zip tie. Unfortunately, there is an explanation as to why HP may have used the zip tie outside of securing it to a socket. From what I understand, crystals are mechanically vulnerable, and can even be influenced by their relative position. The zip tie could have been used to stabilize it on the cheap. I hope it is your assumption that prevails! Then I could just pop it out.Any yes, the crystal does get in the way of one of the daughter board mounting holes. Removing it would solve the mounting problem as well!Thanks again for your help!!! I have a board and some components on the way from Luthor2K. The MV85 I have coming from Ebay. Once I have the board ready, I will cut the zip tie, and the soldered or socketed question will be answered. I will let you know!Mike

author: amc184
author_rank: Regular Contributor
timestamp: July 04, 2020, 08:40:06 am
content: Mike has asked me for a better bill of materials for the PCB, and I thought I'd post it here so anyone building this PCB in the future can see it.C101 and C105: 330µF 35V Ø10mm THT low impedance electrolytic capacitorNippon Chemicon EKZE350ELL331MJ16SElement14,Mouser,DigikeyC102, C104 and C106: 100nF 100V THT 5mm pitch metalised PET capacitorWima MKS2D031001A00KSSD or MKS2D031001A00MSSDElement14,Mouser,DigikeyC103: 10µF 63V Ø5mm THT general purpose electrolytic capacitorNippon Chemicon EKMG630ELL100ME11DElement14,Mouser,DigikeyC107: 1nF 400V THT 5mm pitch metalised PET capacitorWima FKS2G011001A00KSSD or FKS2D011001A00MSSDElement14,Mouser,DigikeyJ101: 2.54mm pitch THT pin header, 10.8mm total length, 6 wayAmphenol 68000-204HLFElement14,Mouser,DigikeyR101 and R105: 100R DIN0204 size THT metal film resistorWelwyn MFR3-100RFC or Vishay MBA02040C1000FCT00Element14,Mouser,DigikeyR102: 680R DIN0204 size THT metal film resistorWelwyn MFR3-680RFC or Vishay MBA02040C6800FCT00Element14,Mouser,DigikeyR103: 560R DIN0204 size THT metal film resistorWelwyn MFR3-560RFC or Vishay MBA02040C5600FCT00Element14,Mouser,DigikeyR104: 20kR 25 turn THT potentiometer with staggered leads and side adjustment screwBourns 3296Z-1-203LFElement14,Mouser,DigikeyU101: LM1084, LM1085 or LM1086 type TO220 adjustable linear voltage regulatorST Micro LD1086BVElement14,Mouser,DigikeyX101: Morion MV85A C20F-5V-SINI bought mine on eBay, at the time these were a compact, cheap and power efficient option with the right output type and level.Other things you'll need:Two UNC6-32 threaded spacers, male to female type with a 7/16" body length to mount the board. You'll also need a couple of 6-32UNC machine screws.An M3x10mm machine screw and two M3 nuts.A TO-220 heatsink, such as a Wakefield 274-2ABElement14,Mouser,Digikey.When mounting the heatsink the M3 machine screw should go through from the underside of the board, then have the following stack; PCB, M3 nut, heatsink, TO-220 voltage regulator, M3 nut. The first nut is important, it spaces the heatsink off the PCB. Make sure the head of the screw isn't so large that it's bigger than the diameter of the area clear of groundplane on the PCB. You don't need to use insulating hardware to isolate the voltage regulator from the heatsink unless it's touching something conductive, which it shouldn't be.

author: amc184
author_rank: Regular Contributor
timestamp: July 17, 2020, 11:22:27 pm
content: In the bill of material I previously posted I used an adjustable voltage regulator, but it's possible to use a fixed one as well.In the original design an adjustable LM1086 is used, which needs a resistive divider to set its output voltage. R101 and the parallel combination of R102 and R103 form this divider - I used 560 and 680R in parallel to make a divider for 5V without having to use anything other than standard E12 series resistors. C103 is optional, improving ripple rejection. The ability to add C103 is one of the advantages of an adjustable regulator - most fixed regulators do not give access to the feedback node to add this capacitor (though some do).When using a fixed voltage regulator R101, R102, R103 and C103 are not needed. Pin 1 of U101 should also be connected to ground, the neatest way to do that is to fit a zero ohm jumper to the R102 pattern. So the changes to the bill of materials would be:C103: do not fit.R101 and R103: do not fit.R102: DIN0204 size jumperVishay MBA02040Z0000ZCT00Element14,Mouser,DigikeyOr use a piece of wire, but the jumper will look neater.U101: LM1084, LM1085 or LM1086 type TO220 fixed 5V linear voltage regulatorTexas Instruments LM1086CT-5.0Element14,Mouser,DigikeyA couple of things to note about voltage regulator choice in this circuit:Both the fixed and adjustable versions of LM1084 / LM1085 / LM1086 regulators use the same pinout; 1: adjust or ground, 2: output, 3: input. This is the same pinout as many adjustable resistors (such as the LM317), but is not the same pinout as most fixed regulators. For example, the LM7805 uses 1: input, 2: ground, 3: output.Most linear voltage regulators are damaged if the voltage at the output becomes higher than the input voltage. In this circuit this may happen if something was shorted on the input rail, taking it down to 0V while C105 is still charged. An LM1084 / LM1085 / LM1086 regulator builds a protection diode in to avoid this situation, but many regulators do not. When using an LM317 or similar these need to be provided externally. This board does not include reverse bias diodes, so for this reason I would avoid using the LM317 or similar here.

author: pizzigri
author_rank: Regular Contributor
timestamp: September 09, 2020, 07:56:01 am
content: Hello to everyone in the thread! And what a great thread this is. There’s a 5316A coming my way, and I just was looking around for a tear down to see what to expect and maybe some repair advice and bam! The OCXO mod....So I’m hooked, is anyone willing to part with a spare board? I’m located in Italy....

author: reddish75
author_rank: Regular Contributor
timestamp: January 13, 2021, 06:48:20 pm
content: I have a 5316A which hopefully works properly but have a question, how do you display the frequency inputted on channel B?

author: David Hess
author_rank: Super Contributor
timestamp: January 17, 2021, 06:48:11 pm
content: Quote from: reddish75 on January 13, 2021, 06:48:20 pmI do not think you can. The A input can be routed to both the A and B channels using the "SEP/COM A" button.

author: W8RLC
author_rank: Newbie
timestamp: November 18, 2021, 02:48:35 pm
content: I know you specifically built this TXCO for use with the HP5316A. I have an HP5314A and was wondering if this replacement could be adapted for use with it.

author: amc184
author_rank: Regular Contributor
timestamp: November 22, 2021, 09:16:01 pm
content: I don't think this board will work well with an HP 5314A. Unlike the 5416A, 5416B and 5415A it does not include the same plug in position for a frequency standard. I do see a position for a TCXO option on the rear PCB of the 5314A, so it looks like there may be a way to upgrade it, but not using the same PCB as the others.You could look at making an option for the 5314A, but it might be easier just to get a 5416A instead. They regularly sell for less than USD40, and have a better feature set anyway.

author: beastor
author_rank: Newbie
timestamp: March 21, 2022, 12:20:08 am
content: Picked up a 5316A with the 1GHz C input from eBay. Checked it against my Louis Scully GPSDO and it was out by 23Hz, but the adjustment screw was already at the maximum, so I decided to use the board from amc - it works a treat!Even though mine didn't have the 'Option 4' marked on the rear, it looks like it had that retrofitted afterwards? Semi-officially?Picture included below of the board I replaced.Thanks again amc!

author: alitronix
author_rank: Contributor
timestamp: May 14, 2022, 12:35:19 pm
content: Hello , I have the HP 5315 A model unit with fried transformer ,can anybody tell me the transformer deliver 2x8 or 2x7 AC V? (on 5315A model)I can't find it on manual (sorry in case if is there the value and i miss it) .If I put 2x9V or 2 x10V it is ok? (this what I have ).Thanks in advance.

author: bdunham7
author_rank: Super Contributor
timestamp: May 14, 2022, 01:46:01 pm
content: Quote from: alitronix on May 14, 2022, 12:35:19 pmThe unregulated DC supplies are +/- 7.5V and they have the 4-way line input selection (100/120/220/240) which sort of indicates to me that they anticipate that unregulated supply will be within 10% or so of nominal. Increasing the transformer voltage would add heat stress to the regulators and I don't know how much they can tolerate.I measured the transformer output on my 5316B for you to compare to (it should be the same circuit) and with the unit off but plugged in--which means the unregulated DC bus is powered and on mine, the OCXO is warm--I get 15.4VAC. With the unit powered on I get 14.6VAC. So I'm guessing that an appropriate transformer would be 7.2V nominal and about 8.0V no-load on each winding if you were using a 2-winding transformer in a CT configuration. 9 or 10VAC would probably work at first, but may burn something up in short order.

author: alitronix
author_rank: Contributor
timestamp: May 14, 2022, 02:16:18 pm
content: Thank you for support ,It is impossible to find here in Europe a 2X7 VAC transformer at a reasonable price...I just find on eBay a 2x8 VAC ,is not the same old stile format but I will be able to put in with no hardware changes ,I believe will be OK for the moment and meantime I will search for a original one or something very similar.I powered it up with external AC variable power supply just for test and seems to work fine.Thank you for help, much more clear now.

author: hvontres
author_rank: Contributor
timestamp: December 30, 2022, 12:46:36 am
content: Hi, I was wondering if anybody had any spare PCB's for the OCXO option? I will be getting a 5316A soon and would like to install one. if not, I'll go and get some made at PCB way.

author: softfoot
author_rank: Contributor
timestamp: January 09, 2023, 10:33:20 pm
content: A very interesting thread - I wonder if anyone in the UK has a spare OCXO board for the 5316A ??Please contact me offline if so.Many thanks,Dave

author: hvontres
author_rank: Contributor
timestamp: January 20, 2023, 05:52:44 am
content: Quote from: hvontres on December 30, 2022, 12:46:36 amI have three extra PCB's in the US if anyone is interested.

author: hvontres
author_rank: Contributor
timestamp: February 14, 2023, 10:03:27 am
content: Finally got my board working and installed. Turns out a lot of cheap LM317 Voltage regs use the LM317-L die internally, so even though they look like a full fleged 1.5A regulator, they crap out at 200ma. I almost returned my two OCXOs since they really don't run well on 2.5V instead of 5V. Once I put in a nice vintage LM317-T, the board has been working great.

author: Kjo
author_rank: Regular Contributor
timestamp: March 05, 2023, 02:05:44 am
content: I have collected maybe 6 versions of the 5315A/B 5316A/B over the years. The earliest 15A is series 1928A (1978-78), but there are 4-5 series even older. None of these had an option 004 OCXO as far as I can determine. Up through the 1928A at least, the basic 10Mhz osc was on main A1 PCB. And the 6pin jack was used for a TCXO.The series 2xxxA look to have eliminated the A1 osc for a basic, TCXO, OCXO plugin oscillator. I think this is important because pin 6 of J2 is used differently in various 5315A/B as well as in the 5316 series.Unfortunately, only the 5315 series 1824 service manual in the wild has complete schematics. (Although I have an OEM manual for the 1928A series.) The bottom line I am getting at is that the amc184 PCB gerbers tie pin 1 & 6 together and this could be a problem for some 5315 PCBs. It is best, I think, to not include a pin 6 when working with a 5315.Feedback desired.

author: Kjo
author_rank: Regular Contributor
timestamp: March 05, 2023, 04:25:26 pm
content: Another thing that bugs me about equipment manuals on the internet is the abundance of incomplete pdf files. There are dozens of HP5315 manuals missing section 8 and all the schematics. There also seems to be a level of ignorance in that the series prefix releases in this type of equipment. Manuals that match the series one has in hand are indispensable.Unfortunately, keysight only published a very early 1978 complete manual. There were more than a dozen series after that. I would like to see schematics from a 21xxA series.

author: Kjo
author_rank: Regular Contributor
timestamp: March 06, 2023, 09:38:28 pm
content: I finally got out all 3 of the HP5315A units I have and measured the behavior of the pins on J2. I have a 1928A, 1948A & 2536A. I only have schematics for the 1928A. There are certainly many revisions to the schematics over the many series. Some of the changes have to do with the battery pack I think. Nobody should plan on using an OCXO with a battery pack!Here is how pin 1 & 6 behave across the three series I have.1928A/1948Apin 6 - always 10+VDC if plugged inpin 1 - 9+ VDC if plugged in and standby/On in ON AND ONLY IN FREQ/PERIOD mode.2536Apin 6 - always 10+VDC if plugged inpin 1 - 9+ VDC if plugged in and standby/On in ON but unaffected by FREQ/PERIOD switch.I havent yet figured out why HP used the FREQ/PERIOd switch this way in the early series yet.This tells me that pin 1 & pin 6 are not common across the series and that for the 5315A meter the pin1 of the 004 clone should not be used.Using pin 6 only will power the OCXO as long as the meter is plugged in.The 5316A/B may be different. I have 2 of these to check next.

author: aeg
author_rank: Regular Contributor
timestamp: March 07, 2023, 07:32:08 am
content: Another gotcha with the service manuals is that the 1812A through 2032A prefixed instruments have a slide switch inside to select between the optional oscillator and the oscillator on the A1 board. The manuals for those prefixes say to flip the switch when installing a TCXO or oven option. Since prefix 2120A and above don't have this switch, the 2120A and later manuals removed this step from the installation procedure. There is no mention of the change in the backdating section of the newer manuals! The previous owner of my 5315A had field installed the TCXO option and evidently had used the new procedure on an old instrument. It was still set to use the standard oscillator, and the TCXO board was sitting uselessly inside doing nothing. I discovered this a few years after purchasing the instrument when I opened it up to calibrate it. It also had a sticker from the previous owner's in-house cal lab...Also no mention in the manual's backdating section about the supply voltage change from 3.0V to 2.85V.

author: Kjo
author_rank: Regular Contributor
timestamp: March 09, 2023, 11:25:28 pm
content: Yea, I have 2 5315As with that switch and an integrated crap oscillator.After looking at my 4 5315As & 3 5316As I can say, for the series I have, DONT use pin 1 with a 5315A.It likely doesn't matter with the 5316A/B an pin 8 is apparently unconnected. You MUST use pin 1 to getun-switched DC power.Another thing is that some 5315As have threaded rivets in the A1 PCB for mounting the external OSCand others just have a gold plated #6 hole requiring removal of A1 to access the retaining nut. Not a big deal,but a surprise none the less.What and where are you referring to a supply voltage change from 3 to 2.85?

author: Kjo
author_rank: Regular Contributor
timestamp: March 09, 2023, 11:44:23 pm
content: Many thanks to AMC184 back in 2014 for the original design of this circuit. It had survived many revisions and hashelped many owners to greatly improve an otherwise mediocre counter. I revised the gerbers from AMC184 recentlyto allow fitment in all HP5315A/B and HP5316A/B series that I know of.I have built 5 of these using the Morion MV85 and they work perfectly. Not willing to let a good thing pass,I operate a small business and I decided to assemble some part kits with everything needed to repeat this by anyone with basic soldering skills.I have 2 kits, one with and one without the MV85. (the MV85 is readily available from China on eBay or Aliexpress if you want towait 30-40 days!)Everything is through-hole and assembly can be completed in 15-20 minutes.At this time I have the kits on my website @:https://www.hollywoodcontrols.com/phpHP/HP004OK.phpWhen time permits I may add them to my eBay store for those who love eBay.

author: aeg
author_rank: Regular Contributor
timestamp: March 10, 2023, 10:49:53 am
content: Quote from: Kjo on March 09, 2023, 11:25:28 pm5315A prefix 1832A through 2032A have A1R12 factory adjusted for 3.0+-0.01V at TP+3, prefix 2120A+ changes the trimmer reference designator to A1R11 and it is set for 2.85V+-0.01V at TP+3. What difference it makes to operation, I don't know.

author: Kjo
author_rank: Regular Contributor
timestamp: March 10, 2023, 08:59:52 pm
content: QuoteInteresting, as that is the termination/reference bias source for the MRC high speed signals from the channel input conditioners.My 1928A service manual has A1R12 (287 ohm) in the collector of Q2 Colpitts onboard crystal oscillator. R15 is the adjustment pot for the 3VDCsupply. I think the onboard oscillator went away with the switch in series 2XXX+.I wonder if the part numbers for the MRC are different. I have only ever seen one part number.

author: aeg
author_rank: Regular Contributor
timestamp: March 10, 2023, 10:20:56 pm
content: Oh, there's an inconsistency in the 1832A manual. The reference designators shown in the adjustments section don't jive with those in the schematic. There are no reference designators printed on the PCB itself.The MRC is 1820-2139 in the 1832A parts list, but it changes to 1820-2312 in the 2120A parts list.

author: Kjo
author_rank: Regular Contributor
timestamp: March 11, 2023, 02:14:40 pm
content: Interesting,,,I've only ever seen MRC 1820-2312 labeled parts. My earliest meter is a 1928A series.In the late 1970 this MRC may have been a challenge for HP to mfgr with yield. It was a bipolarchip with everything from ECL to IIL inside.My paper manual 1928A (1979) has those grey-over photos with part reference designators printed overcertain parts.Double check your parts list though. My list says 1820-2312 for HP part number (col 2) but 1820-2139 for Mfgr part number (Col last).It lists HP (28480) as Mfgr. Dont know why HP would use 2 different numbers for same part, but # on packagehas seemed always 1820-2312.

author: aeg
author_rank: Regular Contributor
timestamp: March 11, 2023, 10:44:01 pm
content: 1832A and 2120A series parts lists have matching "HP" and "manufacturer" part numbers. I guess for 1928A they decided to compromise. 1820-2139 labeled parts do exist in the wild:https://www.flickr.com/photos/anachrocomputer/43289590070(not my photo). 2120A manual also has modification notes for substituting 1820-2312 for 1820-2139 in early units - see one of the 05315-90021 scans, p. 117 or p. 118 depending which scan you have.

author: Kjo
author_rank: Regular Contributor
timestamp: March 13, 2023, 03:08:49 pm
content: @aegThanks for that confirmation photo!

author: Kjo
author_rank: Regular Contributor
timestamp: August 31, 2023, 12:14:30 am
content: I have assembled three different kits for this OCXO design which is compatiblewith both the HP5315A and HP5316A.Everything is through-hole and assembly can be completed in 15-20 minutes.At this time I have the kits on my website @:https://www.hollywoodcontrols.com/phpHP/HP004OK.phpWhere you can get the kit with or without the MV85 oven oscillatoror just the single PCB.If you prefer eBay you can get the same thing at:https://www.ebay.com/itm/155741314023But eBay takes about 25-30% of sellers price which includes listing price, shipping and sales tax.So the prices are higher.

author: AMR Labs
author_rank: Frequent Contributor
timestamp: January 05, 2024, 01:30:51 pm
content: Anybody know if the HP5316A/B uses reciprocal counting for the lower frequencies? so measurements are fast and accurate even in the low Hz range. If not, is there a similar HP model that does use reciprocal counting? Thank you.

author: bdunham7
author_rank: Super Contributor
timestamp: January 05, 2024, 03:18:51 pm
content: Quote from: AMR Labs on January 05, 2024, 01:30:51 pmYes, it is a reciprocal counter and will give you an accurate reading in one gate cycle.

author: pqass
author_rank: Super Contributor
timestamp: January 05, 2024, 03:23:08 pm
content: Quote from: AMR Labs on January 05, 2024, 01:30:51 pmAccording to3-4 of the 5316A operating manual: "To maximize resolution, the 5316A uses a reciprocal counting technique for frequencies below 10 MHz, automatically switching to conventional frequency counting for frequencies above 10 MHz."

author: AMR Labs
author_rank: Frequent Contributor
timestamp: January 05, 2024, 04:21:54 pm
content: Quote from: pqass on January 05, 2024, 03:23:08 pmThanks guys, then indeed I was looking at the correct model. Its a pain having to wait 10 seconds before getting a low Hz reading with my current counter, specially when trying to make fine adjustments to a 60Hz oscillator.

author: hvontres
author_rank: Contributor
timestamp: January 05, 2024, 05:11:31 pm
content: A few things to keep in mind:1) If you don't need GPIB, a 5315B will have the same features. In fact, the main microcontroller used is the same mask from part. The oscilator mod works on both.2) The OXCO mod is well worth it if you can't find one with the factory option3) If possible, I would look for a unit that has the third channel installed. That will allow you to go up to about 1.2 Ghz or so.

author: AMR Labs
author_rank: Frequent Contributor
timestamp: January 05, 2024, 06:29:01 pm
content: Quote from: hvontres on January 05, 2024, 05:11:31 pmYes, ideally looking for installed options 003 and 004, although I have other counter for higher frequencies so C-Channel would be nice to get but not indispensable. My main goal is having something that will count low Hz frequencies without the typical 10 second gate time. And that OCXO board shown earlier in this thread seems easy enough to build if missing.5315 and 5316 model form factor is very similar to 3468 and 3478 DMMs. BTW still looking for a handle for my 3468A.

author: bdunham7
author_rank: Super Contributor
timestamp: January 05, 2024, 06:47:08 pm
content: Quote from: AMR Labs on January 05, 2024, 04:21:54 pmWhat is your current counter? If it is not reciprocal, then even with a 10-second gate you will only have 1 decimal point, 60.0Hz?

author: AMR Labs
author_rank: Frequent Contributor
timestamp: January 05, 2024, 08:05:51 pm
content: Quote from: bdunham7 on January 05, 2024, 06:47:08 pmExactly, I just get one decimal. That is why I would like a reciprocal counter.I still can get 5 decimal places like 60.00000Hz with the build-in CTT option of my 2465B, but for this application I would rather need a dedicated separate counter like the HP5315/16.As a GP counter I use the Optoelectronics 8010a up to 1.1Ghz that came with the OCXO option. Also have an Audio Frequency Meter build into the COM-120B with the lowest range being 0-200Hz but it also defaults to only 60.0 with just one decimal as at the lower end is rather meant to mostly count low frequency signaling tones like CTCSS, so one decimal resolution is more than enough for its intended application.

author: Freddy36
author_rank: Newbie
timestamp: May 05, 2025, 01:49:34 pm
content: It seems the older HP 5315A have a negative Voltage on Pin 1 (about 9 Volts -) Counter is from 1980 and has Orange Digits.I seems there are a lot of differences in the 6 Pin Timebase Header, an clearly differences between 5315 and 5316.At the begin of the threat shown Timebase PCB wit the Morion Mv 85 are pin 1 and 6 together. At the 5315 this is a Short between Vcc+ anf Vcc- and the Mainfuse will blow directly. So for my HP 5315A i have to cut Pin 1 to get OCXO Pcb working.On my HP 5316 are no Problems.just for information...