Agilent 66332A Dynamic DC Source 20V/5A Repair and mods - Page 1
Forum section: electronics / testgear

author: Berni
author_rank: Super Contributor
timestamp: May 28, 2016, 10:54:03 am
content: So i got my hands on a Agilent 66332A. While it looks like a run of the mill rack mount power supply it is actually a SMU. This means that apart from being a power supply it also has reasonably accurate readout (Not a terribly impressive 4 1/2 digits here) and has the capability to sink current to act as a electronic load. However it is limited to positive voltages only. It is possible to get true 4 quadrant operation if you have option 760, this adds a relay to the output that allows it to swap its output terminals around so its not the most elegant way or doing it. But these things can be found on ebay for under 200 bucks!Mine however is a 120V unit so it had to be a case of "Don't turn it on, take it apaaaart" in order to swap some internal connections to turn it in to a 230V unit. And since i am taking the lid off i might as well take some photos.The transformer has quite a complicated rats nest of wires on it with no indication of what is what so you do need to consult the service manual on how to wire it up for 230V or vice versa.

author: Berni
author_rank: Super Contributor
timestamp: May 28, 2016, 11:18:01 am
content: Now you may have noticed the word "Repair" in the title. This is because the unit was being sold as not working and indeed when i powered it up all you get is a transformer buzz. After a bit of looking around i quickly noticed that a tantalum cap was looking rather toasty on the digital board. As you can see its pretty much black and since tantalum caps tend to blow in to a short circuit this would be a pretty good reason why the unit doesn't want to turn on.After a quick pray to the electronics gods i desoldered the capacitor in hopes that that it didn't blow due to the supply rail being too high. Put everything back together, powered it on and HEYO it boots up fine with no errors. Checked its output with a multimeter and it was working perfectly! That was a pretty straightforward fix.While it does work without any capacitor there its still better to replace it. None of the same footprint tantalum caps in my parts collection had a 35V voltage rating so i instead put in a 10uF 63V electrolytic cap with the leads bent for SMD mounting.I also found another issue with the unit in that the knob on the front was really lose and wiggly, but it seamed to still work. For that i pulled off the front panel and once the board was out the problem was pretty obvious on visual inspection. Looks like someone gave the knob a really good knock in order to rip the top part of the encoder off. This looks worse than it actually is. I was able to bend the tabs back in to place and i also added a drop of super glue to each one to hopefully hold it a bit better. After that the knob felt as good as new and worked perfectly.

author: Berni
author_rank: Super Contributor
timestamp: May 28, 2016, 11:34:07 am
content: At this point the unit was in fully working condition, but before i close the lid there is one more thing on the list. I want to use it as a bench unit so front pannel terminals are a very useful thing. Luckily there is a option for this so there already are prepared cutouts in the front panel for the connectors. All we have to do it punch a hole in the front panel sticker and mount a pair of binding posts on there. For wiring them in there is a connector at the back where i ran a nice thick 2,5mm2 wire.Once i had the unit all back together i gave it a calibration. It was very good on voltage out of the box but the current was off by a little bit. Its a pretty easy process where you just punch in some numbers in to the front panel. Here is the final result. The only problem with this unit is that setting currents under 2mA becomes inaccurate, but this is normal.

author: Macbeth
author_rank: Super Contributor
timestamp: May 28, 2016, 04:02:21 pm
content: It's essentially the same as my HP 6632B, but with some extra commands in the firmware to turn it from a SYSTEM DC POWER SUPPLY to a DYNAMIC MEASUREMENT DC SOURCE.

author: TheSteve
author_rank: Unknown
timestamp: May 29, 2016, 12:10:40 am
content: I have a 6632B as well, from the pics they do look the same, likely just a firmware change. I also added front mounted binding posts.I got mine for 25 bucks as it displayed "bad int" when powered up. Of course it was wired for 220 VAC and the seller tested it on 110 VAC. I re-jumpered the transformer and it has been great ever since.

author: BFX
author_rank: Frequent Contributor
timestamp: May 29, 2016, 12:34:03 pm
content: I also use wires for sensing and different terminals configurationI have also this wiggly knob on my second unit, waiting for repair in near futureThanks for hint

author: gslick
author_rank: Frequent Contributor
timestamp: May 30, 2016, 03:08:15 am
content: Quote from: TheSteve on May 29, 2016, 12:10:40 amMy Agilent 66332A serial number MY4300xxxx has firmware version A.01.03 in an M27C202-70K6 OTP EPROM (2-Mbit, 128Kx16) with the part number 5080-2513 etched on it.Attached is a binary dump of my 66332A firmware version A.01.03 if you are curious enough to try loading it on your 6632B. I also have a couple of 6632B and haven't gotten around to trying that myself yet.

author: TheSteve
author_rank: Unknown
timestamp: May 30, 2016, 04:05:56 am
content: Awesome, I'll likely try it at some point.btw, my 6632B info: HEWLETT-PACKARD,6632B,0,A.01.04Comparing the boards they certainly look to be the same with the same components installed. I just took a picture of my 6632B mainboard specific details.

author: KJDS
author_rank: Super Contributor
timestamp: May 30, 2016, 07:22:23 am
content: I've repairs dozens of wiggly knobs on 6632B supplies.It takes very little force to do displace the top part of the encoder, it's one of the few design issues with them.

author: Berni
author_rank: Super Contributor
timestamp: May 30, 2016, 08:22:24 pm
content: That is interesting. I would have expected there to be extra circuitry in there to provide the current sinking functionality. Or do 6632B supplies also sink current if you ask them to?I forgot to take a photo from that corner of the board and the unit is already put together and on a shelf.Oh and on a side note i just got a HP 6624A 4 channel system PSU. But due to my stupidity i bought one that fails self test.Turns out channel 1 is dead. It looks like its a complex internal circuitry fault that Dave would love to do a repair video on. I haven't got any further in my limited time due to how unnecessarily complicated the guts of the thing are, but if there is interest i could document the repair process a bit.

author: TheSteve
author_rank: Unknown
timestamp: May 30, 2016, 08:27:04 pm
content: Yes, the 6632B does sink current very nicely. You can even set the max current unlike some other Agilent supplies.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 30, 2016, 08:54:49 pm
content: Indeed, they're really excellent pieces of kit if you're in the habit of designing products that use rechargeable batteries. Try to 'charge' a standard bench PSU and you'll be in a world of hurt. On a 663xB, you just get to see your charging current and terminal voltage displayed on screen

author: Berni
author_rank: Super Contributor
timestamp: May 30, 2016, 08:58:27 pm
content: Quote from: TheSteve on May 30, 2016, 08:27:04 pmI looked trough the manuals a bit and they indeed say they can sink. Only difference i can find to the 66332A is that this so called Dynamic source can play back 2048 points at up to 64KHz sample rate. That's easily something that might as well just be a software thing.I am surprised they don't put something special in the name to tell you its a supply with sink capability. As far as i know such functionality is quite unusual to see in a regular PSU.Oh and i also noticed that the heatsink gets very warm when you leave the output just turned on but without any load. So they must be using a pretty high bias AB output stage on it.

author: nctnico
author_rank: Super Contributor
timestamp: May 30, 2016, 09:58:22 pm
content: Quote from: AndyC_772 on May 30, 2016, 08:54:49 pmIndeed. I have the 66332A little brother 66311B and it occured to me it is perfect to simulate a battery in an upcoming project.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 31, 2016, 06:26:29 am
content: Quote from: Berni on May 30, 2016, 08:58:27 pmThey put something special in the price!

author: Berni
author_rank: Super Contributor
timestamp: May 31, 2016, 08:06:40 am
content: Quote from: AndyC_772 on May 31, 2016, 06:26:29 amHence why i tend to get things that say HP or Agilent on it from Ebay.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 31, 2016, 09:06:06 am
content: Sure, me too! 3x6632B, 1x6633B and 1x6634B at last count...

author: PTR_1275
author_rank: Frequent Contributor
timestamp: August 18, 2016, 10:07:50 am
content: I just got my 66332a delivered and took it out of the box. It wasn't packaged the best and the knob has taken a bit of a hit. I took the unit apart to change the transformer taps for 240VAC, took the front panel apart and forced the knob clips back together. It is holding, but not the best and I would prefer to replace it.Looking through the service manual it is saying the front PCA has no user replaceable parts on it. Do any of you have a part number for the rotary encoders you have used as replacements?The power supply also seems to be a bit on the noisy side (hum wise, not electrical noise wise) and it seems to be coming from the big filter caps right beside the transformer. I will investigate a bit more and see if anything needs replacing. It has date codes from late 99 / early 00, so it is 16 years old.Out of curiosity, has anyone flawed a 6632B power supply with the 66332A firmware and seen if it works?

author: Berni
author_rank: Super Contributor
timestamp: August 18, 2016, 11:18:26 am
content: Mine has a lot of audible transformer hum too and yes the fan is loud.I have not been able to fix any of that. The hum is likely coming from the transformer being such a flat design, giving it a lot of leaking magnetic field around it and that then vibrates the top and bottom case covers. As for the fan i found that it can't be run slower than it already does. When the output is enabled with no load at all the heatsink still gets pretty hot due to the bias current of the output stage.As for the encoder i have no idea what the part number is, but from a glance it does look like a standard part. Try measuring the distance between the pins and the height of the shaft and comparing it to the similar looking parts on Digikey.

author: Micke
author_rank: Regular Contributor
timestamp: August 18, 2016, 11:35:20 am
content: I bought encoders at good price from Ebay, a seller in Germany.This encoder is common in a lot of other HP/Agilent gear, so getting 10pcs is nicehttp://www.ebay.com/itm/10x-Inkremental-Encoder-12fach-ALPS-EC16-ohne-Rastung-/302025367910?hash=item46521d6166:g:3KIAAOSwrx5UYhWb

author: artag
author_rank: Super Contributor
timestamp: January 27, 2017, 11:49:13 pm
content: Quote from: gslick on May 30, 2016, 03:08:15 amThat firmware contains this list of power supplies. Presumably it supports them all, though I don't know how it decides which one to be. Maybe a factory calibration option, or a link.HP6611C HP66312J9 HP66312J8 HP66311J1 HP66311B HP66308AHP66332A HP66312A HP66311AI have only the 6632B. It has EPROM AM27C2048 5080-2573 A.01.04There are 2 other programmable devices that might be customised though - a xilinx config rom 1736e marked 5080-2527 and a PAL 126V8 marked 5080-2528. Are the same parts fitted to the 66332A ?

author: AndyC_772
author_rank: Super Contributor
timestamp: January 28, 2017, 07:48:49 am
content: It's all in the service manual:Quote

author: Berni
author_rank: Super Contributor
timestamp: January 28, 2017, 08:39:59 am
content: Quote from: AndyC_772 on January 28, 2017, 07:48:49 amOh neat, so the service manual tells you how to hack it in to a higher up model.

author: BFX
author_rank: Frequent Contributor
timestamp: January 28, 2017, 05:34:37 pm
content: Front terminals changed to much nicer oneshttp://www.tme.eu/en/katalog/#search=BS-244MN&cleanParameters=1Old one here:)https://www.eevblog.com/forum/testgear/agilent-66332a-dynamic-dc-source-20v5a-repair-and-mods/msg951238/#msg951238

author: Berni
author_rank: Super Contributor
timestamp: January 28, 2017, 08:40:04 pm
content: Quote from: BFX on January 28, 2017, 05:34:37 pmThose do look rather nice, very close to the stock ones that originally come on HP gear.I did want to add sense terminals to the front panel of mine....i should buy some.

author: Macbeth
author_rank: Super Contributor
timestamp: February 03, 2017, 11:30:14 pm
content: Quote from: TheSteve on May 30, 2016, 08:27:04 pmIt's a 2 quadrant supply, but isn't there a simple board upgrade that is documented in the schematics using relays to turn it into a sorta 4 quadrant? Like a super cheap SMU?

author: TheSteve
author_rank: Unknown
timestamp: February 03, 2017, 11:51:00 pm
content: There is option 760 which is a polarity reversal relay.

author: artag
author_rank: Super Contributor
timestamp: February 04, 2017, 12:35:40 am
content: There's also app note 5990-3949http://www.keysight.com/main/redirector.jspx?action=ref&cname=EDITORIAL&ckey=1703016&lc=eng&cc=GB&nfr=-35712.384349.00which describes using two power supplies for 4-quadrant operation. It's a bit crude : it just uses them like an H-bridge, so to get full range you have to ensure the supplies are set to opposing voltages. But it does cross zero without a relay glitch.

author: Berni
author_rank: Super Contributor
timestamp: February 04, 2017, 08:33:59 pm
content: Yeah there is a connector inside where a little board with a relay fits that simply swaps the terminals around. I thought about DIYing it to upgrade mine but never bothered.Quote from: artag on February 04, 2017, 12:35:40 amNow that's a nice trick i didn't know about. Dang it i only have one unit tho!

author: dxl
author_rank: Regular Contributor
timestamp: February 08, 2017, 08:47:29 pm
content: Did anyone ever tried to upgrade the Firmware from 6632B to 66332A?

author: AndyC_772
author_rank: Super Contributor
timestamp: February 08, 2017, 09:53:39 pm
content: I don't think it's actually a firmware upgrade as such, just a configuration setting.Isn't there an extra board in the 66332A that does the dynamic signal capture?

author: eliocor
author_rank: Unknown
timestamp: February 08, 2017, 10:30:15 pm
content: What firmware memory chip (EPROM) is mounted on 66332A?I can try to replace the one mounted on my 6632B with a new one with the 66332A firmware but I'd like to know what exact chip is used.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: February 09, 2017, 06:54:12 am
content: I have a 66332a with option 760 (polarity reversal relay) and a 6632b. The 6632b arrived with a smashed screen that I've bought the parts to repair but in between changing jobs and moving house that's not been anywhere near a priority.When I get some time I'll get the screen fixed and see if changing the option in the menu unlocks it to a 66332a. I'll out of curiosity also check if the 66332a reduces functionality if I set it as a 6632b.I don't recall seeing any extra boards or component types for the dynamic measurements.

author: ElektroQuark
author_rank: Unknown
timestamp: February 09, 2017, 08:54:38 am
content: I have a 6611C, what is it missing from the rest of the family?

author: Narmaraktuk
author_rank: Contributor
timestamp: April 16, 2017, 08:15:20 pm
content: Many thanks for taking the time to put this up Berni. My 6632B also had a shorted tantalum on the control board, mine was only nearer to the board edge (so say one up in your picture). Seeing someone else with similar issues made for a short repair

author: dxl
author_rank: Regular Contributor
timestamp: April 18, 2017, 07:17:53 pm
content: Checked with my HP 6632B but i'm not able to select the HP 66332A type with the calibration setting. Maybe i find some time during the next day to see what firmware it has.

author: gslick
author_rank: Frequent Contributor
timestamp: April 18, 2017, 11:26:48 pm
content: I have dumped firmware version A.01.03 from my 66332A.I'll have to check and see what firmware version I have in my 6632B.I have't tried putting the 66332A firmware in the 6632B yet.

author: mtdoc
author_rank: Super Contributor
timestamp: April 19, 2017, 01:17:22 am
content: Quote from: Narmaraktuk on April 16, 2017, 08:15:20 pmYou might want to have a look at Dr. Frank's discovery re: a small design/manufacturing goof on these supplies as spelled out inthis thread.I recently picked up a 6632b but have not gotten around to the fix yet. I also have a 6632a. They're excellent PSUs. The current sinking feature is a bonus!

author: mark03
author_rank: Frequent Contributor
timestamp: August 16, 2017, 05:10:53 pm
content: I recently acquired six (!) of these supplies (and one 6632B) at auction. All but one were wired for 240V. After I figured this out and changed the transformer connections per the service manual, they are mostly working. A couple have broken displays, and a few have wobbly knobs. My first PCB inspections did not reveal any failed capacitors. I haven't performed Dr. Frank's fix yet.Here's the strange thing: Measured on a scope, all of the supplies have ~ 3 Vp-p ripple at 115 to 125 kHz on the output. Every single one!! This screams "operator error" to me, but I cannot figure out what could be causing it. Any ideas?

author: carl_lab
author_rank: Frequent Contributor
timestamp: August 17, 2017, 11:38:19 am
content: Quote from: mark03 on August 16, 2017, 05:10:53 pmOpen sense connections?Dead output electrolytic caps?

author: mark03
author_rank: Frequent Contributor
timestamp: August 24, 2017, 04:12:19 am
content: Quote from: carl_lab on August 17, 2017, 11:38:19 amSense connections are in place. All of the rail and bias voltages in Table 3-3 check out. There are a bunch of signal voltages on J307 (between the A2 digital and A1 power boards) that I still need to verify, once I can figure out how to probe them safely.I think the problem is somewhere in the CV control loop. When the supply enters CC mode the oscillation vanishes and the output looks good.I still can't understand how all six of these supplies would have the exact same [previously unreported here] failure, unless they were all abused in precisely the same way. These came from the Megown T&M auction a few months back.

author: Berni
author_rank: Super Contributor
timestamp: August 24, 2017, 05:25:52 am
content: Perhaps show us some scope screenshots and describe how you measured it.Oh and does the fast/slow switch on the back do anything? Its supposed to be used to keep it stable with long cables on slow.

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 24, 2017, 06:09:23 am
content: Quote from: mark03 on August 24, 2017, 04:12:19 amAs they probably come from the same batch or company, they might all have been set up or specially modified for that '332 dynamic thingy stuff.Maybe you search through all their settings first. As far as I remember, the 6632B has some capacitors parallel to the output, which might be removed in the 332A (just speculating).. what about applying an external cap?Or do they have jacks on the front?Btw.: this tantalum cap error is present in the 6632B only, afaik.Frank

author: mark03
author_rank: Frequent Contributor
timestamp: August 26, 2017, 05:48:35 am
content: Quote from: Berni on August 24, 2017, 05:25:52 amSure (see attachment). This was measured with an ordinary 10x scope probe between positive and negative outputs. Note that the average voltage is exactly correct (4.0V), open circuit or under a modest load (50 ohms). But if the current limit is tripped, the oscillation goes away and the output is perfect.QuoteFunny you should mention that! On all six of my units, there is no switch, only a hole in the chassis covered with a silver sticker, and wire jumpers to fix the unit in the "normal" (slow) position. The stickers are colored and sized perfectly; it appears to be a professional job, or perhaps manufactured that way? In any case, per the user manual p. 27 ("Fast/Normal Operation"), this setting should have no effect for open circuit or resistive loads. The only issue would be if capacitance were added in the "fast" mode.I checked the voltages on J307 (connector between the analog and digital boards), and thought I'd found a smoking gun when OV_SCR, the crowbar control, was 0.64V instead of the stipulated 5.0V. A check of the schematic, however, reveals that OV_SCR can never be higher than a diode drop above ground. I keep finding these small mistakes in the HP documentation, which unfortunately has the effect of making me doubt all of my earlier findingsFWIW, here's a photo of my analog PCB. There are definitely some variances with the service-manual schematic. For instance, U313 (in the current monitor amp) is an AD712 instead of an LM358 as shown; its gain is 2 instead of 1 as shown, due to R427 being a 10k resistor instead of a jumper; and the connection to R427 is made with a bodge wire. And these observations are just from one small area, since the wire caught my attention. Perhaps I have an early revision of the PCB?Quote from: Dr. Frank on August 24, 2017, 06:09:23 amActually, on my 66332A the error is still there. I haven't changed anything yet because the bias voltages are all within spec, but if I did, what type of capacitor would you recommend? The SiBaTit ones you used are no longer available.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 26, 2017, 07:04:51 am
content: Instead of SiBaTit caps one can use normal MLCCs, just keep in mind the capacitance reduction with applied high DC bias for some types. The SiBaTit caps were just an early brand name of relatively high capacitance ceramic caps. Now they go as as X5R and similar.The AC signal looks a lot like oscillation. A bad output capacitor (could be just too much ESR) could be a cause. So adding another low ESR cap to the output is definitely worth a try. Even if it does not stop the oscillation it would be interesting so see if the frequency is changing.Changing the current monitor should not change much in CV mode.The missing fast/slow switch might indicate the compensation is not as normal - the capacitor (and maybe resistor) values determine if it is slow, fast or something prone to oscillation.

author: nctnico
author_rank: Super Contributor
timestamp: August 26, 2017, 08:31:19 am
content: Perhaps these are special order units tuned for a very specific load. I'd try a large capacitor at the output to see if the oscillation stops.

author: AndyC_772
author_rank: Super Contributor
timestamp: August 26, 2017, 08:38:17 am
content: I might also suggest taking a look at the voltage control feedback loop, and comparing the values of the parts actually fitted against the schematic. Perhaps also remove the main board, take a look at the solder side, and check to see if any parts have obviously been replaced since the board came off the production line.If the units were a special order, there's a 99% chance that they started out life as tested, working, standard products, which were then changed by hand.If the fast/slow switches are missing, then your units have definitely been intentionally modified. Also, that modification specifically relates to the transient response in some way, which points a smoking gun at the control loop, IMHO.

author: mark03
author_rank: Frequent Contributor
timestamp: August 27, 2017, 11:16:38 pm
content: Thanks for the suggestions. I had time to look at this again today, and indeed, a 470 uF capacitor across the output stops the oscillation. Not being an analog guy, I am hazy on loop compensation. Could someone explain why adding capacitance would push the output into stability? For voltage feedback, I thought capacitive loads generally reduced stability.AndyC's suggestion to look at the PCB solder side was a good one. I was able to catalog all of the modifications, and it's quite a list, although more components were deleted than anything else. I picked a good unit to examine, too, because comparing the A1 board from another of my supplies with this first one, there were a couple of differences: First, the other board looked newer (same PCB rev A3 however), and second, the deleted components were not snipped off like on the first unit; they were never soldered in to begin with. Definitely a factory modification.At this point I should probably skip ahead to what I think is the answer. I should have noticed the white "J02" stickers on the back of my supplies. This appears to denote a custom option. I could find no mention of it for the 66332A, but Helmut-Singer has an old document on their web site for the 66312A (a very similar supply):http://helmut-singer.de/pdf/hp66312a.pdfSee pages 6-10. The listed component changes don't seem to bear any relation with what I found through reverse engineering, but perhaps the reference designators are different between these supplies? Here are some choice quotes:QuoteQuote(why an inductive series resistor, and why so hefty?)QuoteI was intending to add front binding posts and use a couple of these as bench power supplies. It sounds like I could just add Ccomp and Rcomp internally and be OK, although the supported range of load impedances is considerably narrower than the standard unit.

author: Berni
author_rank: Super Contributor
timestamp: August 28, 2017, 05:28:04 am
content: Well loop stability can become a complex topic when there are lots of components involved. One case where slowing down the output with a capacitor can help when the control loop has some delay added up trough it while the output reacts very quickly. This causes the control loop to ask the output to rise and because it doesn't see it rising yet it keeps asking it to go up, by the time the control loop notices its rising the output has already went significantly above the desired value and once that comes around to the control loop it asks it to go down sharply. So slowing it down gives more time for the slow control loop to react to its changes.But yeah usually capacitance is what causes instability, but perhaps the control loop here was tuned to expect a certain amount of capacitance. I wouldn't take those load specs in the datasheet too seriously since clearly the modification messed with the control loop tuning, perhaps it can now handle far beyond 400uF.

author: mark03
author_rank: Frequent Contributor
timestamp: August 28, 2017, 03:35:18 pm
content: Quote from: Berni on August 28, 2017, 05:28:04 amNo, those specs are for the J02 option. A stock 66332A allows for a much wider range of load impedances, at least tens of thousands of uF in normal mode, or significant inductive loads in fast mode. I'm just hoping that mine can tolerate flying leads of reasonable length, with the compensation components installed inside the unit.I'm also trying to figure out why an electrolytic cap with ESR ~ 250 mohm (matching the spec in the J02 document) wouldn't be just as suitable as the film capacitor / ww resistor series combo.

author: nctnico
author_rank: Super Contributor
timestamp: August 28, 2017, 03:38:16 pm
content: As written in the text above a electrolytic capacitor has too much leakage so the current readback won't be accurate down to the uA level.

author: OP27
author_rank: Newbie
timestamp: November 13, 2017, 05:43:18 pm
content: Hi all,I am currently repair the device HP66332A.The my device has a broken front cover. (transparent display cover, VFD it is OK)Where i can buy parts? I need the whole front cover.I found the part number (service manual agilent): "5063-3426" Front Panel Assy, Std unit.Nowhere can not find this partThe part can also be used. Thank you for any help.

author: little.tesla
author_rank: Regular Contributor
timestamp: December 09, 2018, 10:05:10 pm
content: Hello,I know this is an old topic but I'm trying to get a copy of the original file which was located athttp://helmut-singer.de/pdf/hp66312a.pdfUnfortunately the company switched off their website and removed all files. I'm interested in particular regarding the custom mod J02 and I think there should be actually more mods described.Can anybody help out?Thanks in advance.Best regards,Dimce

author: Berni
author_rank: Super Contributor
timestamp: December 10, 2018, 06:19:02 am
content: What is the PDF supposed to contain?

author: little.tesla
author_rank: Regular Contributor
timestamp: December 10, 2018, 07:01:59 am
content: mark03 with its "Reply #47" posted a text snippet describing the custom option "J02" of the 66312A. I'm hoping the other options (like J03 J04) are described in this document as well. I'm unable to find any information on the internet regarding this options. The newer manuals from Agilent don't mention them at all.

author: korlatos
author_rank: Regular Contributor
timestamp: December 10, 2018, 04:25:43 pm
content: I have the PDF file but couldn't upload it due to size limitations (>1MB). So I created a split ZIP file - part 1 is attached.

author: korlatos
author_rank: Regular Contributor
timestamp: December 10, 2018, 04:29:49 pm
content: Part 2 of the ZIP file. Please rename it to file.z01 before you attempt to combine them (eevblog doesn't allow upload of a file with a z01 extension).

author: little.tesla
author_rank: Regular Contributor
timestamp: December 10, 2018, 07:40:52 pm
content: Thank you very much for the file. I really appreciate it!

author: Dwaine
author_rank: Frequent Contributor
timestamp: December 11, 2018, 01:46:00 am
content: I just bought a Agilent 66332A and looking forward to the suggestions of putting front connectors with sensor wires.

author: Berni
author_rank: Super Contributor
timestamp: December 11, 2018, 06:26:12 am
content: I might also need to get a broken one of these because it appears to use the same front panel as another instrument i'm working on (N3300A Load mainframe).The problem is that a lot of the time something that is sold broken for parts is often easily fixable and then i feel bad stripping it for parts and am motivated to try and get a more broken parts unit.

author: Dwaine
author_rank: Frequent Contributor
timestamp: December 30, 2018, 07:18:39 am
content: Quote from: gslick on May 30, 2016, 03:08:15 amMy device has firmware A.00.08.... Looks like it was used once. Just after it was unboxed from its initial purchase.

author: beanflying
author_rank: Super Contributor
timestamp: December 30, 2018, 07:29:22 am
content: Quote from: Dwaine on December 11, 2018, 01:46:00 amShould be much the same as what I did on my 6632B as per the photo below. I should have used some more upmarket Jacks I guess I used what I had at the time. The Gold plated link bars are modified audio ones.

author: Dwaine
author_rank: Frequent Contributor
timestamp: December 30, 2018, 07:38:34 am
content: Quote from: beanflying on December 30, 2018, 07:29:22 amI think they look great. I really like the link bars!

author: beanflying
author_rank: Super Contributor
timestamp: December 30, 2018, 07:44:59 am
content: The Bars came from these guys.https://meniscusaudio.com/product/gold-shorting-barspr/There online site doesn't love overseas transactions but you may do better at least being in the area.Standard 19mm 3/4" spacings between the sockets as I sometimes use dual Pamona style jacks.

author: matches
author_rank: Contributor
timestamp: January 01, 2019, 12:52:46 pm
content: Hi and a happy new year.I'm new to this forum. Recently I picked up a 66332A and found usefull intel here. Immediatley I installed a third bodge (2 were already there) with the two ta caps not beeing ground referenced as Dr. Frank found and reported.Thank you very much. The caps on mine seemed fine so I left them in. I think it does not have seen a lot of usage.So I'd like to share some intel and quirks with you.Attached you find foto of the inside. If you look really closely, you may spot two bodges on the interface board.As some stated, the fan is a littla on the noisy side. On mine it had dust accumulated unevenly which leads to more vibration (see the dusty picture).Papst has added a very small weight to balance it out, so I think this dust is noticable. After a clean it is better but still too noisy for my taste.It's a Type 612 with rated 40 dBA with 24 cfm of max. airflow. Found a data sheet on dogo key (https://media.digikey.com/pdf/Data%20Sheets/ebm-papst%20Industries%20PDFs/600.pdf)When switched on, it is run at approx. 8 V, so it is regulated. In the schematics there is a HS_Therm signal wired to pin 14 going to the interface board.Yet I cannot find any sensor at the heat sink.

author: matches
author_rank: Contributor
timestamp: January 01, 2019, 01:00:18 pm
content: So here is detailed view of the interface board.On the back it says HP, the label on the front says Agilent, but looks like slaped on.And, despite the very good condition, the knob was a little loose as well.

author: Berni
author_rank: Super Contributor
timestamp: January 01, 2019, 01:17:41 pm
content: Yeah depending on the period its from you can get mixed HP and Agilent branding at times. The dark gray plate you got peeling off is actually one of the standard "nameplate" formats that are also used on other gear they make, so its possible the older ones that say HP are also glued on. For some gear all they do is swap the tiny silver HP bade with the Agilent star logo without it actually saying Agilent anywhere on the front.At least they put more effort into it back then. If you get gear from just the right at the Keysight transition period you can get a scope where they simply put a little Keysight sticker on top of the exiting nameplate where the Agilent logo is. Naturally that sticker quickly found its way into the trash can. Tho upon updating the software there was suddenly Keysight logos in every possible place (On windows based scopes they even change the Win 7 login screen background and the desktop background to a giant full screen logo). By now i got a bit more used to the Keysight branding, but when they announced it i found it being the stupidest name ever.As for the fan. Well if you put some engineering effort into it you could fit a blower cage style fan in here that could provide the same airflow with much less noise. You probably just need a 3d printed adapter to be able to mount it on. But then again even without the fan, then the transformer hum in this thing would then start to becoming the noisy part. Im guessing there is so much audible hum due to the strangely very flat E core transformer leaking a lot of field and vibrating the top and bottom covers panels.I found a higher power alternative to my Agilent 66332A in the form of a Agilent 6050A (DC Electronic load mainframe), but you should hear the fans in that thing! There are two 120mm all metal casting fans running from 110V AC and use 20W each. Luckily the thing is so heavy that it doesn't end up flying off the bench when the fans turn on. I seen these huge 110V AC fans in other gear too so i plan on making a 110V speed controller board for them.

author: matches
author_rank: Contributor
timestamp: January 01, 2019, 01:23:51 pm
content: As for the front terminals. In the servica manual it is stated to cut some jumper resistors (R456 to R459).If all of the 4 pins of the connector for the FP option is used, the current flows to the front and back to the rear if the load is connected there.If the load is connected at the front, two of the 4 wires carry the voltage back to the rear, so the sense terminals at the back can be used and they read the voltage at the front terminals.One interesting thing: the service manual also has a schematic of the board for the front terminals.They have included some caps a 4700 pF, 250 V and a 220 pF, 1 kV in parallel from each terminal to mains earth.I wonder why that is. Some compensation for the additional cunductor and its inductance? Just capacitive coupling to earth?If I were to add them should I use ceramics like X7R or NPO, or should I rather use foil caps?As for the binding pist and the shorting links.Pomona has the nice binding posts Model 3760https://www.pomonaelectronics.com/products/hardware/binding-post-tin-platedThey have also the shorting links Model 4115https://www.pomonaelectronics.com/products/hardware/shorting-link-binding-postsThe posts are available gold plated as well as Model 3750. They even have a low thermal EMF version, Model 3770. But I think thats not needed here.Although in the metal case there is only a small cutout, the binding posts shhould fit. There is enough clearance.Especially when using a mounting base. Which I'd prefer because of the pre cut front panel. I think it then gives more stability.The base:https://www.pomonaelectronics.com/products/hardware/mounting-base-double-binding-post

author: matches
author_rank: Contributor
timestamp: January 01, 2019, 02:13:00 pm
content: Haha I can imagine the meeting where they decided to change the name."Hey we haven't changed our name in a while. Lets change it to Keysight.""Ouh yes, good Idea! "Haha.. but as long as the performance and quality is there.Funny, I've never seen a sticker as a label. They could have sold it as Agilent anyways.I have checked with some older Pomona binding posts. They do fit. No interference with the metal casing.There is like 1/4" clearance.

author: Berni
author_rank: Super Contributor
timestamp: January 01, 2019, 04:32:15 pm
content: Here is what the stickers look like (Photo found on google).Well in this case they didn't put it over the Agilent logo. But they put this sticker on when the instrument was sent in for a calibration.

author: beanflying
author_rank: Super Contributor
timestamp: January 02, 2019, 12:12:13 am
content: Quote from: matches on January 01, 2019, 01:23:51 pmI did see that on the schematic too but as I am as from the bush I just hacked into the back of the rear terminals and used 16AWG wire for the sense lines to minimize any voltage drop. The Caps to Earth might be worth adding to mine so I will load it up and have a proper look for any stray signals on the output. Since I did that I also now have some plated copper shield I should put around the run with an outer of heatshrink as it passes close to the AC end.Also need to look at doing the Mods as per Dr Franks thread that I hadn't seen beforehttps://www.eevblog.com/forum/repair/agilent-6632b-fault-repair-and-several-design-flaws/msg1018796/#msg1018796Death to the TantyPhoto of my butchery

author: Berni
author_rank: Super Contributor
timestamp: January 02, 2019, 12:35:59 am
content: Ah them darn tantalums again. Much like my repair of a blown tantalum on the digital board.Then again at least they tend to be a easy fix. A shorted power rail is easy to notice and usually the caps catch fire so its easy to spot the black charred mess on the board so that you know exactly what capacitor to replace.If they all look fine then just Ohm it out, or my method where i get annoyed and i just hook up a high current power supply to the shorted rail and let it push a ton of current in. At some point something gets hot, or catches fire to point me where the problem is.

author: Ussovak
author_rank: Contributor
timestamp: January 04, 2019, 02:54:44 pm
content: The User manual clearly explains the difference between using the front posts and rear terminals.See attached.

author: tuanpq
author_rank: Newbie
timestamp: September 24, 2025, 01:17:21 pm
content: Does anyone have the full schematic diagram?

author: Andy Watson
author_rank: Super Contributor
timestamp: September 24, 2025, 01:38:07 pm
content: Quote from: tuanpq on September 24, 2025, 01:17:21 pmI have not yet found the full diagram. The 66332A appear to be identical to the 6632B but with different software. The service manual for the 6632 provides the schematic for most of the analogue stuff but not the A2 interface board.

author: tuanpq
author_rank: Newbie
timestamp: September 25, 2025, 04:20:25 pm
content: i think even the A1 drawing in the document has something wrong. for example the voltage gain stage, when the current is negative.