Repair : HP 3245A precision DC/AC source  - Page 1
Forum section: electronics / repair

author: TiN
author_rank: Super Contributor
timestamp: October 30, 2015, 11:14:57 am
content: I feeling not truly exited about outcome of last HP gear repair, so I decided there is more to it.Let's the community work this one out, will see how good our Hewlett-packard EEVBlog fanboys know their T&M lineup.I have new piece of gear in-transit at this moment, and while I'm waiting for it, let's take a guess, what is it?Almost sure that I'm hinting too much, but anyway, here's piece of photo of it:Give me your ideas! Person who guess correctly will win a prize, mention in creditsP.S. Ones who know may remain silent.

author: deadlylover
author_rank: Frequent Contributor
timestamp: October 30, 2015, 11:17:59 am
content: 3245A universal source?I *think* it shared the same chassis as 3458A.

author: TiN
author_rank: Super Contributor
timestamp: October 30, 2015, 11:18:43 am
content: Man, why you kill all the suspense?

author: crispy_tofu
author_rank: Super Contributor
timestamp: October 30, 2015, 11:24:40 am
content: wOw, that was fast

author: deadlylover
author_rank: Frequent Contributor
timestamp: October 30, 2015, 11:28:09 am
content: I only recognised it because I was previously 'tricked' by it when I was browsing 3458A listings on Taobao (Chinese Ebay).

author: lukier
author_rank: Unknown
timestamp: October 30, 2015, 11:35:37 am
content: Awesome TiN!I was looking for 3245A on eBay for a while, but they go for pretty penny.There is very little info on these devices online. Service Manual is not very detailed, but I think CLIP can be bought (paper?) from equipment manual vendors.I'm extremely curious how they pulled off 6.5 digit precise DC voltage output. Nowadays one would just buy AD5791B and Bob's your uncle. Jim Williams AN86 20 bit DAC would be probably too slow to settle both DACs and correct with ADC readings.Another option is PWM. AFAIR this is the way DAC is implemented in some Fluke calibrators. It still surprises me that Fluke made PWM DAC precise, need to figure out how they did it at some point.

author: TiN
author_rank: Super Contributor
timestamp: October 30, 2015, 11:35:43 am
content: Quote from: crispy_tofu on October 30, 2015, 11:24:40 amYah, too fast... Moooods! Remove this guyOk.One I boughtis sick and broken (surprised?), so it will be a full teardown and worklog on it too. Should be here somewhen next week, I hope. I could not resist to win it at $344 (+175 for shipping, yeah, it's big and heavy 15KG).

author: Vgkid
author_rank: Super Contributor
timestamp: October 30, 2015, 03:47:07 pm
content: Looking forward to it.

author: TiN
author_rank: Super Contributor
timestamp: November 03, 2015, 04:27:58 am
content: Box is here.Should I make teardown tuesday video?

author: Vgkid
author_rank: Super Contributor
timestamp: November 03, 2015, 04:34:37 am
content: twiddling my thumbs.

author: TiN
author_rank: Super Contributor
timestamp: November 03, 2015, 04:36:49 am
content: I can even try livestreaming, if one know good online streaming engine, since Youtube borked theirs.

author: tec5c
author_rank: Frequent Contributor
timestamp: November 03, 2015, 05:07:07 am
content: http://www.yawcam.com/??

author: TheSteve
author_rank: Unknown
timestamp: November 03, 2015, 06:13:43 am
content: Yes please to a video tear down.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: November 03, 2015, 09:32:57 am
content: I'm going to guess error 82 and has the high voltage option in it.I was bidding on it, but good to see it go to a good home (even though it isn't on my bench)

author: dom0
author_rank: Super Contributor
timestamp: November 03, 2015, 09:57:27 am
content: Quote from: lukier on October 30, 2015, 11:35:37 amPWM filtered by integrators is extremely linear. It is basically the counterpart to timing/integrating ADCs.

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 03, 2015, 10:05:12 am
content: Twitch.tv maybe? Looking forward to it!

author: TiN
author_rank: Super Contributor
timestamp: November 03, 2015, 11:15:16 am
content: Twitch needed to install 3rd party garbageware (which not even working right on my Win2008).Ustream it is.I'll do proper video with camera as well, so don't expect much from cheapie webcam.

author: TiN
author_rank: Super Contributor
timestamp: November 03, 2015, 10:17:19 pm
content: I'll post details later (6am here, not slept yet!), but in two words : It was easiest repair in the world, did not even need to heat up soldering iron.Here are some internal goodies:Cleaning front panel:Vishay hermetic foils on HV board (4pcs 40K000 and one 4K4):

author: lukier
author_rank: Unknown
timestamp: November 03, 2015, 10:47:21 pm
content: Quote from: TiN on November 03, 2015, 10:17:19 pmGreat job!Get some sleep and let us know what was the issue. I remember the eBay listing (even asked the seller for the shipping cost but in the end it was too much) and it showed some errors.Thanks for sharing the CLIP - PWM DAC indeed! (and 12 bit high speed DAC in low resolution mode). Interesting to see so many switching power supplies in a precision instrument (even for the inguard section).Nice to see mostly off the shelf parts, except few hybrid resistor networks in the analog section and gate arrays (PWM DAC controller etc).I see you added a bit of foam around LM399 to keep it nicely warm and cozyStrangely enough, in the CLIP LM399 zener current is sourced from 5V. Heater uses GND and +18V. I remember other Agilent gear using +-15V for the heater and there was some discussion that this is a more stable arrangement

author: lowimpedance
author_rank: Super Contributor
timestamp: November 03, 2015, 11:00:59 pm
content: Nice score , whats the bet it was a dirty or loose connector/socket.A welcome change from the prior HP experience Im sure.

author: TheSteve
author_rank: Unknown
timestamp: November 03, 2015, 11:20:59 pm
content: Front panel connector loose? This rivals my last ebay score - HP network analyzer that was sold as dead, was a dirty 110/220 VAC switch.

author: Vgkid
author_rank: Super Contributor
timestamp: November 04, 2015, 03:40:14 am
content: Thanks for the teardown. I assumed that it would bear some resemblance to the 34401A, but nope.

author: TiN
author_rank: Super Contributor
timestamp: November 04, 2015, 04:12:46 am
content: Why 34401? This beast does not even have ADCArticle with more photos and detailsAs you can get hints from article, I plan to do some modifications and tweaks, such as replacing voltage reference with LTZ1000 module and adding lower gain output boards, so I could generate accurate low-noise millivolts/microvolts. There are two open BNC openings in front panel face, so I can install triax connectors for extra outputs.

author: Vgkid
author_rank: Super Contributor
timestamp: November 04, 2015, 05:08:37 am
content: Prices(1988 catalog pg 430) $4200 base, 2500 2nd channel, 400 waveform software option, option 002 is not in this edition.

author: lukier
author_rank: Unknown
timestamp: November 04, 2015, 03:37:15 pm
content: Hi TiN,if in the future you'll be playing more with 3245A internals, would you mind probing XMSP/XMSN and XSLP/XLSN signals? I'm curious what is the scheme employed there, PWM or pulse density, what PWM frequencies (as we have 200 Hz and 194 Hz low pass filters), center aligned and complementary PWMs or what.I'm analyzing their PWM DAC circuit and it is a bit cryptic due to the sheer number of analog switches involved in all the modes (and probably selftests). In HiRes scenario LSB PWM is connected with the MSB via RP100A resistors ?, then through low pass filter, but the LSB has its own path and LPF as well and both of them can be switched to the common DAC output. In these scenario the HS DAC seems to provide DC offset. In high speed scenario the LSB+MSB DAC seems to provide DC offset (called vernier)?Very interesting device indeed. Maybe with HV option and LTZ1000 it could as well replace these bulky EDC voltage/current standards.What INL can one expect from such PWM DAC? Linearity is not specified in the 3245A datasheet AFAIR, but if they say it is 6.5 digit I would assume 1 ppm.

author: sdk.61
author_rank: Contributor
timestamp: November 05, 2015, 09:14:43 pm
content: Hp 3457A mult?meter ?

author: Vgkid
author_rank: Super Contributor
timestamp: November 06, 2015, 05:06:26 am
content: Quote from: TiN on November 04, 2015, 04:12:46 ammeant 3457, wrong decade.

author: TiN
author_rank: Super Contributor
timestamp: November 06, 2015, 03:20:53 pm
content: Fun with ARB function :

author: PTR_1275
author_rank: Frequent Contributor
timestamp: November 06, 2015, 03:29:31 pm
content: That is really awesome.

author: dom0
author_rank: Super Contributor
timestamp: November 06, 2015, 03:35:36 pm
content: Now that's just arbitrary.

author: Vgkid
author_rank: Super Contributor
timestamp: November 07, 2015, 12:27:24 am
content: Impressive.

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 07, 2015, 12:38:10 am
content: +1, fantastic!

author: TiN
author_rank: Super Contributor
timestamp: November 09, 2015, 05:25:56 pm
content: Both brothers assembled and ready for testing and initial DIY calibration

author: babysitter
author_rank: Frequent Contributor
timestamp: November 10, 2015, 05:46:54 am
content: Gee your 3458A has that nasty display bug showing gibberish at the last digits! See! Those Frankennumbers.I will gladfully do the waste disposal for you.

author: deadlylover
author_rank: Frequent Contributor
timestamp: November 10, 2015, 07:12:06 am
content: Grats mate, I don't dare to ask how much damage the 3458A repair did to your wallet.Next time you have a fiddle around, can you please check what the residual reading is with inputs shorted for the ACV range on the 3458A? 10mV/100mV range on analog mode, just ballpark readings will do, cheers.

author: TiN
author_rank: Super Contributor
timestamp: November 10, 2015, 10:24:53 am
content: ACV.. Hmm, that's interesting, I'll run noise script modified for ACV, just like we did on DCV before.What AC mode should I use? Not familiar with them yet.

author: TiN
author_rank: Super Contributor
timestamp: November 13, 2015, 09:27:39 pm
content: I think better late than never. Here's repair video and some testing. Hope you will not be bored.Also took a closer look on source board... Guess what, DAC was replaced before. Somebody did not bother cleaning fluxLittle lumped inductor made me smile:Don't you love it?Voltage reference upgradeGood bye, good old HP-marked LM399...Added pair of coax wires instead. What was heater power now becomes LTZ module power. What was zener diode, now is Kelvin-connected LTZ1000ACH output (different module used, not the exact one from photo). Took photo with older module since it's the only one without insulation wrap around..Removed resistors R400 and R401, as these not needed anymore. Unit is powered and hooked to DMM to log output. It's out of cal ofcourse, but no big deal, as we recalibration is easy with just 3458A.Here's warmup graph, 40 minutes span. It's slow and ramping...

author: Vgkid
author_rank: Super Contributor
timestamp: November 13, 2015, 09:57:21 pm
content: Impressive

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: November 13, 2015, 10:05:48 pm
content: Wait until you see the next project. Fluke 87V with LTZ1000!Don't ask about battery life.

author: TheSteve
author_rank: Unknown
timestamp: November 13, 2015, 10:19:51 pm
content: Quote from: ManateeMafia on November 13, 2015, 10:05:48 pmThe best 4.5 digits of your life!

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 13, 2015, 11:49:50 pm
content: Can't wait!!

author: nidlaX
author_rank: Frequent Contributor
timestamp: November 14, 2015, 12:12:04 am
content: Quote from: TheSteve on November 13, 2015, 10:19:51 pmDon't give Fluke the wrong idea. We don't need voltage standard wars between multimeter manufacturers like they did resolution wars for digital camera sensors.

author: TiN
author_rank: Super Contributor
timestamp: November 14, 2015, 07:00:26 am
content: Hmm, no good.Perhaps I should hook more DMMs to log LTZ itself (7.1V) and +11.6V output REF, to see if it's output stage drifting, or issue with reference circuitry.Also I'll separate heater drive power, as I suspect that one..

author: TiN
author_rank: Super Contributor
timestamp: November 14, 2015, 09:36:59 am
content: Aha.Separated heater supply from opamp supply, now it's playing nice. Trap for young players, pay attention of proper signal and power current paths on your precision designs, or it can easily cause utter failure like in post above.Also rigged some measurement, source running open cover with ref module hanging on side.LTZ itself stays ~0.4ppm window over last hour (measured via 2002)3245A output set to 10V on DMM (actual output setting is +9.71203V) stays within 0.35ppm (meas with 3458A) in last hour.Ambient temps +28.3°C (no AC in room, to prevent pesky airflow).For those who still feeling dizzy grasping all these PPM scales, here's same 1ppm division graph:Day and night, eh?Now time to pack unit back in with covers, run it few hours to get thermal equilibrium and perform calibration.I tried calram backup tools from 3458A to capture 3245A calibration data, but both linux and windows verisons failed. Seems 3245A using different address for CAL data. Not big deal anyway.P.S. horisontal time frame of latter graphs - ~1 hour.

author: Dr. Frank
author_rank: Super Contributor
timestamp: November 14, 2015, 10:51:21 am
content: Quote from: TiN on November 14, 2015, 09:36:59 amAs the control PCB is exactly the same as in the 3458A, all memory chips must be on the same physical location!If you look onto the 3245A board, it does not have the 2kx8 nvRAM, its socket is empty !It only contains the two 32kx8 nvRAMs (and also the four 32kx8 SRAMs).Therefore, the calibration data probably will also be inside these, but without this elaborate access-lock.Another question is, if the 3245A firmware also contains the hidden MREAD command.Frank

author: TiN
author_rank: Super Contributor
timestamp: November 14, 2015, 11:26:58 am
content: No, it's not empty, there is ribbon cable running to source board. And X2816BP U18 ROM + few RAM and logic on inguard section chips (not battery backed) there as well.It's not socketed, and only DMM needed to do full calibration, so I did not bother socketing RAM.I'll take few more photos with everything in place, to clarify this.

author: TiN
author_rank: Super Contributor
timestamp: November 14, 2015, 07:29:44 pm
content: Few more photos, as promisedTop side:Bottom side:Modification on source PCB:Remove R400, R401, LM399 reference.Solder coax wire in place of LM399's diode location. This connected to Kelvin output (direct connection at LTZ's zener pins).Solder coax wire to +15V and GND to power LTZ's opamps and control circuitrySolder coax wire to +18.5V and power GND to provide separate current path for LTZ's heater, so it would not upset reference output.Now, find a best spot for module location. I think it's best on bottom side, between front panel and HV Opt.002 board. It's far from mains transformer, far from pesky fan.To have it isolated from airflow I added big piece of airlocked foam used in packing electronics.It tied to metal chassis via dual-sided 3M tape, for better contact.Now soldered piece of copper foil for sake of it. It's soldered to ground on power coax wire in single point. Idea to have it for even temperature distribution and bit of shielding. It's likely doing nothing at all, like audiophoolery, but hey, it's shiny and I had it without use anyway. Why not?Piece of 4mm rubber pad is holding everything in place securely, screwed down to existing two metal stubs on chassis. Coax wires not touching anything and running at least 1cm from output wires/front panel.Now, let's calibrate it.Password is standard, but calibration have to be done by GPIB.Temperature in room around +26°C. After entering calibration mode, it's just showing "Calibrating..." and output have voltage or current, which need to be measured by DMM and written back by command "CAL VALUE x.xxxxxxxx". After running all values from cal manual, it automatically saves CALRAM. Optionally you can leave a string with CALSTR "TEXT" later.3458A was ACAL'd and initial calibration was just quick sanity check, to make sure I can get output 10.000V. I did not have too much effort on it to do.It worked well, so I calibrated again, keeping temperature within 1°C span and measuring all at NPLC200Result after calibrationNow I'll leave it overnight without AC, to see how good is tempco.I checked 3458A+EDC MV106 earlier today, outputting 10VDC. That setup had+1.23 ppm/°Ctempco. I hope 3245A with LTZ + 3458A can be better.

author: Dr. Frank
author_rank: Super Contributor
timestamp: November 14, 2015, 08:02:04 pm
content: Hi TiN,on the main controller PCB, the address space for the original DALLAS 2kx8 nvRAM is used for the steering of the analogue board.That's what I meant, that the CALRAM is not installed..Therefore the CAL dump program for the 3458A cannot work.On the analogue board, I found the XICOR X2816, as you already described.This is an EEPROM, 2kx8, therefore should not loose its content.Congrats to the final repair and to this new, nice instrumentFrank

author: Zucca
author_rank: Unknown
timestamp: November 17, 2015, 08:41:10 am
content: CongratsTiN,one day with my (was yours) LTZ module I will do something similar!Quote from: TiN on November 14, 2015, 07:29:44 pmMmm why not place there some silica packs?https://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/msg181096/#msg181096Just because you mentioned audiophoolery....well sometime if it costs nothing I am a proud audiophool!Take Care!Z

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 02, 2015, 06:03:18 pm
content: OK I'll just add onto this thread if it's OK with you TiN...Received my 3245A - end '92 vintage, same 2843 firmware, only ever one factory cal. This is the one with 2 x 10V output. Everything seemed OK for an hour and I was doing some basic cal checks when snap, crackle, pop ... thunder and lightning etc ... it smoked, smelt and flashed a bit and then flipped the mains RCD - despite me turning it off pretty sharpish. I assumed it was the transformer but actually it turned out to be thexxs£$%ss:{@~}@xx^&*xxSchaffner mains filter. Since the filter is outboard of the fuse etc, it has no protection and it smokes 'til it goes pop and relies on a trip somewhere else to protect it - so it's a bit criminal to have a fault like this on it. This was even more galling as I already had a new filter and fan sitting on my desk waiting to be installed. A mess like used sticky engine oil - gory pictures for your amusement. Several hours later, IPA clean up / drilling out the damned rivets and it's operational again. Thinking about it, the switch to 220V from its previous many gears of running at 110V was probably the last straw. Now I'm a bit concerned what else of my HP gear has the same dodgy inlet.BTW TiN - did you write some 3245 / 3458 cal software?Alan

author: deadlylover
author_rank: Frequent Contributor
timestamp: December 02, 2015, 06:38:18 pm
content: The same thing happened to my 3457A, same mains filter too, those Schaffner made in Switzerland ones are cursed. After a cosy life of 100V mains, mine only took 5 seconds to blow when exposed to the full wrath of 240V.Your lab is going to be smelly for weeks.

author: free_electron
author_rank: Super Contributor
timestamp: December 02, 2015, 08:08:30 pm
content: awww , maaaaaan. that 'paffner' puked its guts all over that pretty gpib interface.THe problem in those paffner things is they used those amber colored foil RIFA caps that are notorious to go kaboom...

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 02, 2015, 08:14:13 pm
content: Q'n is what other eqpt has those dodgy parts inside?

author: TiN
author_rank: Super Contributor
timestamp: December 03, 2015, 04:17:15 am
content: Whoa.. I got Delta EMI filter already, but was thinking to replace it later. Now I hear you, and will swap it tonight.No I did not have cal program ready yet, as got carried away with more issues in 3458a insteadCan you post few more photos of your analog side boards, I wonder if any difference there as well.

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 03, 2015, 12:00:56 pm
content: >>> Can you post few more photos of your analog side boardsOK here goes, will put up the highres versions on my website. Bit of a mech design bodge getting the B channel out as you need to move the metal deck due to interference between the support posts and the backplane connectors, duh. Also, it's mounted so you can't get at the component side without taking it out. I can see why, but I think they could have come up with a better solution. Have not compared it detail yet, but both channels look identical ... including a 2nd vref. As they we're clearly borrowing a lot of parts from the 3458A already, I wonder why they didn't use just one 3458A vref for both channels? Noticed one bodge wire on the digital btw. C900 looks tricky to source as it's got a screen connection - not sure how important that is. Plan to write a 3245 / 3458 cal program presently.Alan

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 03, 2015, 12:02:17 pm
content: A side...

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 03, 2015, 12:03:56 pm
content: B side...

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 03, 2015, 12:25:43 pm
content: Spot the difference...

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 03, 2015, 01:32:56 pm
content: Large images fyi:http://anagram.net/nuts/3245A/images/BTW I notice there's no internal shields on the 3245.A.

author: TiN
author_rank: Super Contributor
timestamp: December 03, 2015, 02:34:17 pm
content: Thanks.As of reference, I think they saved the effort of characterizing and sorting LTZ's for one more instrument, and it's requirements for "only" 6.5 digit generator is not required. If you really interested, we can do comparisons in drift/stability/noise whatever with yours 3245A and mine LTZ-modded. You have two analog outputs to compareBut i think i need get 3458a stable first...P.S. That D7000 of yours screams for more attention, it can produce much better images...I downloaded all, and had a dejavu moment on few photos. Open EXIF, hm, D800, good camera there.. Then realized it's mine photo

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 03, 2015, 04:40:04 pm
content: >>> P.S. That D7000 of yours screams for more attention, it can produce much better images...Yes agree, v. lame images - I noticed that I had some better images on my phone - and, no excuses, as I have a nice macro lens that I couldn't be bothered to get out...Ho ho, about including some of your images, apologies - I just copied over what I though was interesting from my \3245a\images folder - didn't notice that some of the backgrounds were different.>>> we can do comparisons in drift/stability/noiseGood idea, I'm going to get a measurement set-up sorted out soonish ... atm I can't get ezgpib to talk to anything from win 7 64, so might revert to writing some code myself.A.

author: TiN
author_rank: Super Contributor
timestamp: December 03, 2015, 05:01:56 pm
content: I'd suggest getting RPI so we can bodge some python GPIB sorcery. It's better to have standalone setup to do long-term measurements, so whatever you do on your PC would not upset ppm-level stuffP.s. I use Win2008R2 64bit (it's based on 7 x64) with EZGPIB, it works here okay (with NI GPIB USB pod though, not Agilent you have).P.s. no problems about pic, you can take them surely.

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 06, 2015, 05:10:38 pm
content: OK FYI these are the results I'm getting:3245A setting (V) 0 0.01 0.1 1 10sd (ppm of 10V range) 0.083 0.069 0.18 0.13 0.339sd (ppm of reading) 69 18 1.3 0.339This is with a 3458A at NPLC=1 on the 10V range, no auto zero. I measured the 3458A with a short at 0.053ppm of range.A.

author: TiN
author_rank: Super Contributor
timestamp: December 06, 2015, 05:17:54 pm
content: Paffnerr is out of the way now...Also replaced all electrolytic caps on A6 PCBA, and while doing so, spotted a bit of QC control issue:Little guy's lead was not formed properly.

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 06, 2015, 08:40:42 pm
content: Nice, btw I'm assuming the block of foam you show on the original ref came with the machine? - there was none on mine.

author: TiN
author_rank: Super Contributor
timestamp: December 07, 2015, 12:40:01 am
content: I added that

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 07, 2015, 11:17:05 am
content: Any stats guys here who understand accuracy of noise calculation i.e. how many samples you need to get a given confidence level on the noise figure?I see e.g. this:http://web.eecs.umich.edu/~fessler/papers/files/tr/stderr.pdf...and it looks like it converges fairly quickly.Alan

author: TiN
author_rank: Super Contributor
timestamp: December 08, 2015, 02:10:12 pm
content: 50 samples would be enough, based on results I saw so far.Likely will be best to take 60 samples, and disregard first 10 (as some instruments may have some initial offset from range switch operation).

author: 3roomlab
author_rank: Frequent Contributor
timestamp: December 08, 2015, 03:53:16 pm
content: Quote from: TiN on December 08, 2015, 02:10:12 pmah ok, i get what the sterr.pdf meaning now you said 50. that plot on page 2 fig.1

author: dom0
author_rank: Super Contributor
timestamp: December 09, 2015, 02:29:23 pm
content: Quote from: deadlylover on December 02, 2015, 06:38:18 pmTo be fair it only affects the older ones with the RIFA MP2? caps. New Schaffner filters are as good quality as it gets.

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 09, 2015, 03:26:43 pm
content: Quote from: dom0 on December 09, 2015, 02:29:23 pmDo you, or anybody else know, from which datecode on these Schaffner filters have been improved?Frank

author: VK5RC
author_rank: Unknown
timestamp: December 10, 2015, 02:31:46 am
content: Re Schaffners, some other blogg postees have commented that it seems to be a problem of-old equipment (old IEC filter)- humid environment- infrequent use (build up moisture in cap)- then switch on failure- quite quicklyOccurrence in NOS treated in a similar manner.Looking for a replacement for some older HP gear, Schaffner seems to be one of the better brands. I plan to think of them like electrolytics, need an eye and not infrequent replacement.

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 11, 2015, 10:36:25 pm
content: Ah FYI the DCV cal sequence attached from page 4-6 of the cal manual. Answers on a postcard...

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 11, 2015, 10:55:20 pm
content: Errr...it doesn't want to play - try this...

author: TiN
author_rank: Super Contributor
timestamp: December 12, 2015, 04:31:33 am
content: This is what I had (run manually):

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 12, 2015, 10:11:00 am
content: Any thoughts on what's going on with this algorithm? Why this sequence? Is it exactly fixed or adaptive? There are obviously some checks around the extremities of the ranges - but does anyone have any thoughts on why this sequence in particular? What might the cal data do - some kind of parameterised function applied to the raw reading?

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 12, 2015, 11:16:53 am
content: Ah this is also fairly curious in the cal routine:"Reading number 45 should be taken on the HP 3458A 100V DC range. Autorange should be used for all other readings."And reading 45 is shown as ... 0.100220V.Errr...They wanted the resolution truncated? There's an interaction between the 3458 cal and the 3245 cal? A tech's idea of a joke?A.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 12, 2015, 11:43:03 am
content: For reading no. 45 it is possibly that they need it as a difference to anouther reading that uses the 100 V range. So to avoid extra errors it might be better to use the 100 V range for this low voltage too. The 3458 still has a good resolution in the 100 V range.

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 12, 2015, 12:45:26 pm
content: Hi,FYI I just did an analysis of the commands in the firmware compared to those in the docs (seehttp://anagram.net/nuts/3245a/3245A commands analysis.xlsx). These ones are apparently undocumented and may be interesting:BUSYTIMECALLIMITCALREADCALWRITEFREADFWRITEPICKACHANRIGGLESREADSWRITEWIGGLEThese are there too - similar to the 3458A:JSRMADDRMREADMWRITEA.

author: TiN
author_rank: Super Contributor
timestamp: December 12, 2015, 01:06:02 pm
content: I thought sequence is rather usual, near full scale pos/neg on specific range, near half scale and near zero. Specific points likely chosen for AC performance cal points, by some internal math derivatives.

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 12, 2015, 05:04:59 pm
content: Here's an analysis of the pre-calibration error on my unit. It looks like the 1V and 10V ranges can be compensated fairly easily internally with some linear adjustments. Frankly, I'm surprised that it's so linear.The data is here FYI:http://anagram.net/nuts/3245a/Channel%20A%20vs%20B%20pre-calibration.xlsxAlan

author: TiN
author_rank: Super Contributor
timestamp: December 12, 2015, 06:36:43 pm
content: Nice. Can you share program code, I can try on mine.Can toss in Kei2400 as well for comparison.

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 12, 2015, 07:03:00 pm
content: >>> Nice. Can you share program code, I can try on mine.Hi Tin,Sure, I'll just tidy it up a bit so you don't think I'm a complete hackerHaving decided there was nothing of value in the existing cal - here's the post-cal results. Error is ~5-10uV on the 1V range, +-20uV on the 10V range. I ran the cal a second time and there was no improvement. Allow for minus ~1-2uV error on the 3458A (measured with a short) even though I did autocal the DCV beforehand. Only 0.1C variation over the <1h it took to do these runs.data is here:http://anagram.net/nuts/3245a/3245A post-calibration A vs B.xlsxAlan

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 15, 2015, 09:53:19 am
content: >>> Nice. Can you share program code, I can try on mine.Hey TiN,OK alpha-quality app here:http://anagram.net/nuts/3245A/calibration/- together with example output. It does the performance check as in the cal manual, the calibration sequence, and another pre/post cal check working from +-1uV to +-10V. For DCV only right now - it will be easy to add DCI.It comes up with a calibration 'headroom' number i.e. how far away on average the tests are from the specified error e.g. if the spec says max 30uV error and the actual error is 6uV then the 'headroom' is 80%. As you'll see from the example output, ~80% is actually the kind of number I'm getting.Let me know if you find any quirks/bugs. I would be interested in seeing the output of your runs.Alan

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 21, 2015, 05:58:24 pm
content: OK more cal data - this time DCI:This suggests to me that my box was never calibrated during its life as it was so far out, and it seems easy to pull it way into spec. Cal headroom on DCI is into the 90% i.e. on average it is coming in more than 10x better than the official spec.Data is here if anyone cares:http://anagram.net/nuts/3245A/calibration/3245A post-calibration A vs B.xlsxAlan

author: TiN
author_rank: Super Contributor
timestamp: December 22, 2015, 12:55:58 am
content: I care.Perhaps using logarithmic scales would be more easier to read for DCI? Worth a try, but would need bit of inversion/sign fiddling for negative side...

author: alanambrose
author_rank: Frequent Contributor
timestamp: December 22, 2015, 12:58:49 pm
content: Oh yeah I forgot, it was you who got me into this in the first placeMax DCI error is 5nA < 1mA (5ppm) and ~1nA < 0.1mA (10ppm). I've updated the DCV graphs also. There seems to be a ~+5-10uV offset on my unit on the lower ranges.

author: TiN
author_rank: Super Contributor
timestamp: January 19, 2016, 04:15:45 pm
content: Quote from: alanambrose on December 15, 2015, 09:53:19 amHm, seems you removed app from folder?I got around finally getting VISA back on my Win PC, so wanted to give it a whirl, but no exe anymore.Can you upload it once again ?

author: TiN
author_rank: Super Contributor
timestamp: January 19, 2016, 04:40:17 pm
content: I found it, running now.Seem there is little bug, if frequency a bit higher than 60Hz, program throws error:Code:00:35:27 DMM LOCK OFF sent00:35:27 DMM LOCAL sent00:35:27 *** Connection closed ****** Exception - invalid line frequency '60.0056348' ***I have to rerun it 5-10 times to catch that 59.9x Hz dip to start.Here's data I got:Smoke check logFirst performance verification testPrecal testCalibration logPostcal logPost cal perf test logI'd be happy to test current too, if you have version with it.Also another idea, perhaps results will be bit better if measurements at 3458A would be done with multiple samples, let's say 10-20 samples each step, and ignore first and last 3 samples. Just to make sure it all settle nice and tidy. Maybe run average for remaining samples too. I rerun perfcheck few times, and results were bit different each time.

author: alanambrose
author_rank: Frequent Contributor
timestamp: January 19, 2016, 11:17:53 pm
content: Well v. nice accuracy - do you think this is the result of your LTZ mod? Did you figure out how the LTZ translates to better cal accuracy - not sure I get that yet?Will fix the 60Hz thing and supply the DCI version shortly.Alan

author: alanambrose
author_rank: Frequent Contributor
timestamp: January 20, 2016, 12:00:59 am
content: OK still alpha standard code but V0.2 here:http://anagram.net/Nuts/3245A/calibration/app/V0.2/As you know you can't do DCI cal without DCV so it'll beep at you when it wants the leads changed over on the meter.A.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 20, 2016, 04:32:59 pm
content: Using more smaples at a single point is a good idea - though I would expect the 3458 to give a good reading rather fast. I would still look at the first samples too - they may point to possible settling time after a step in settling. Especially after a large step the voltage can take some time - possibly even more than 10 s to reach it's final value. The most obvieous case would be coming from a high voltage to a a rather small value (e.g. 1 V). Possible source for this could be thermal effects in dividers and dielectric absorbtion.There is absolutely no need to ignore the alst 3 measurements - if you would do that, no need to take that data.

author: alanambrose
author_rank: Frequent Contributor
timestamp: January 24, 2016, 11:28:52 am
content: Hi Kleinstein,Could you explain what you are referring to? The cal executable I provided has a 'SETTLETIMEINMS' parameter (which defaults to 1,000 ms) and a meter 'NPLC' parameter which defaults to 100 - so there's an adjustable wait time to allow the 3245A to settle and an adjustable amount of meter averaging - so the user can (a) experiment and (b) decide for themselves. The official cal procedure is written as though the cal is done by hand (and doesn't suggest a set amount of wait time, but I think, leaves it up to the user to judge) and specifies on page 4-5 'RESET, ACAL, and NPLC 100 on the HP 3458A'.>>> There is absolutely no need to ignore the alst 3 measurements - if you would do that, no need to take that data.Sorry I don't see where the 'last 3 measurements are ignored' - are we looking at the same thing?Alan

author: TiN
author_rank: Super Contributor
timestamp: January 24, 2016, 03:43:12 pm
content: Alan, he was referring to my post with that suggestion.What I meant is to use average of few readings already after settle time elapsed, with few first readings disregarded. I often see that voltages measured are not accurate to last bits if just first reading is taken, even NPLC 100. Sounds fishy, but it could play a bit at very last digits of accuracy.Even after 2 recals using 1s of settling time, I still cannot get 10.00000 reading from 3458A, while gen set to 10.00000. Have to set it 10.00002 or so, to get exact 10V. It's nitpicking, but hey, we doing this for fun here, right?Also I don't think LTZ have anything to do with better calibration accuracy, but I can't prove it, since I never tried it with original LM399 in came condition test.

author: TiN
author_rank: Super Contributor
timestamp: January 24, 2016, 05:26:14 pm
content: CSV data with version 0.2:Perf checkPre-cal checkCalibrationPost-cal check

author: alanambrose
author_rank: Frequent Contributor
timestamp: January 24, 2016, 09:50:47 pm
content: >>> Alan, he was referring to my post with that suggestion. What I meant is to use average of few readings already after settle time elapsed, with few first readings disregarded. I often see that voltages measured are not accurate to last bits if just first reading is taken, even NPLC 100. Sounds fishy, but it could play a bit at very last digits of accuracy.Ahhhhh - I didn't see that text underneath the graph, now I understand.OK will add a count of readings to ignore at the beginning and also a count of readings to average.93% headroom - very nice - will try a recal on mine.Alan

author: klaus11
author_rank: Unknown
timestamp: January 25, 2016, 10:58:50 am
content: TiN, it would be feasible and safe to make a board of Amplification (option 002). For units without 002

author: alanambrose
author_rank: Frequent Contributor
timestamp: January 25, 2016, 11:12:36 am
content: >>> TiN, it would be feasible and safe to make a board of Amplification (option 002). For units without 002That's interesting - mine doesn't have the 002 channel. Care to explain further?>>> I still cannot get 10.00000 reading from 3458AWell a bit ambitious given the specs of the 3245A - but 'nuts' is in our name rightA.

author: TiN
author_rank: Super Contributor
timestamp: January 25, 2016, 11:55:11 am
content: Alan, I'm sure your read my article, aren't you?I cover this right in the intro.You have 3245-001 (option 001, which is two identical +/-10V 0.1A channels), while I have 3245-002 (option 002, on which instead of board B there is x10 power amplifier board, to boost +/-10V to +/-100V, purely analog).

author: alanambrose
author_rank: Frequent Contributor
timestamp: January 25, 2016, 12:21:59 pm
content: Ah yes, I know you have 100V option and I have 2x10V.I was interested in what Klaus had in mind re a non-HP 002 option. It would need to go in a separate box for me as there's little room once you have 2x10V boards installed. Easy enough (well maybe) to build the option from the schematic, but maybe it can be improved / extended.On another subject ... we have a sense of the 3458A and 3245A tempcos now. Well, in both cases, the fan is a simple always-on low-tech thing. So one easy way to reduce drift would be to run the fan from a PID controller. I think to do this well, we might characterise the main components responsible for the tempco a little and then site the sensor(s) near those. What do you think?A.

author: TiN
author_rank: Super Contributor
timestamp: January 25, 2016, 02:01:35 pm
content: Well, making precision +/-100V 4-quadrant amplifier is a task, half a step before actual SMU. Sorta what I have in mind doing for PA stage of my neverending project. That's also one of reasons why I got 3245A in first place, as reference to some extent.Fan control...I'm not ready to open that pandora box yet. As this is looking onto weeks and weeks of careful testing and retesting to make sure those ppm-level values are correct. But I'd love to be corrected.Obvious weak points of 3458A from fan would be tempco of current sense and current source range resistors and networks, perhaps front end input amplifier. Also we don't know if there is any firmware-implemented tempco correction in this aspect, assuming constant fan airflow, as in ADC...

author: alanambrose
author_rank: Frequent Contributor
timestamp: January 26, 2016, 08:21:15 pm
content: >>> OK will add a count of readings to ignore at the beginning and also a count of readings to average.B...x this dumb forum software lost my post....here's the abbreviated version. DCV only, AZERO on, 1s dwell between changing source and making first reading.# ignored # averaged nplc cal headroom %0 1 100 851 1 100 851 5 100 741 10 100 741 10 10 891 30 10 851 100 10 831 1 1000 71(actually I'll post this and add the other results as they arrive)Headroom of 90% means device is 10x better than spec, 100% means perfect device, 0% means on spec (on average over tests). This is with the averaging being done in software rather than in the device.So, with this data at least, the benefit is marginal except for 10 samples of 10 nplc (rather than 1 of 100 nplc as in the cal manual). Looking at the detail, the barrier to a much tighter spec seems to be the low voltage offset - sometimes 10uV which throws off the low voltage sourcing. As the cal algorithm is a black box (e.g. it doesn't seem easy for the user to just adjust the low voltage offset) I'm not sure where to go from here.I guess you could wrap an optimisation algorithm around it and let it run for days but....My simple test set-up (below) - no low emf stuff. Will release this version as soon as I have tested it. This is suggesting to me TiN that your LTZ mod is having a good effect - I see the LM399 has ~15x noise of LTZ1000 so maybe that's it.>>> we don't know if there is any firmware-implemented tempco correctionWell it doesn't seem to work too well if there is

author: TiN
author_rank: Super Contributor
timestamp: January 27, 2016, 02:29:03 am
content: Hm, interesting.Probably does not matter, but I have 3245 and 3458 in different racks, not on top of each other. Also I did not use any fancy cables either, regular 45cm BNC -> BNC-BNC male-male -> 45cm self-made BNC to Copper gold-plated spadelug coax cable.

author: PartialDischarge
author_rank: Super Contributor
timestamp: September 09, 2017, 07:47:30 am
content: So how many are we with the nice 3458 3245 combo? 3?Good news is that mines have no hardware errors. They need a good sanitization, new nvrams, new line filters, maybe new caps and a fresh cal.Started with the first.Feet are missing, will look for 3D models for the printer....

author: TiN
author_rank: Super Contributor
timestamp: September 09, 2017, 08:03:19 am
content: Why bother with printer?There are plenty on evil bay.CalMachineabout to join party too, he just missing 3458.

author: TheSteve
author_rank: Unknown
timestamp: September 09, 2017, 07:13:30 pm
content: I have a 3458A for CalMachine

author: rastro
author_rank: Frequent Contributor
timestamp: September 09, 2017, 07:44:22 pm
content: Quote from: MasterTech on September 09, 2017, 07:47:30 amYou can pick feet up 8 for $8.00.http://www.ebay.com/itm/HP-Agilent-Keysight-5041-8801-Cobb-Grey-Replacement-Feet-Set-Of-Eight-/401400063912?epid=15002971843&hash=item5d754ee7a8:g:VFYAAOSwuLZY2tCA

author: CalMachine
author_rank: Frequent Contributor
timestamp: September 09, 2017, 08:06:35 pm
content: Quote from: TheSteve on September 09, 2017, 07:13:30 pmQuote from: TiN on September 09, 2017, 08:03:19 amFirst, I need to get the 3245A in working order! It's coming with some failures and errors. I also need to work on one of the Datron 1082s I got... the display was acting wonky and going in and out. I think it might have been due to static or something, as display would change and react to my hand being close to it.

author: PartialDischarge
author_rank: Super Contributor
timestamp: September 09, 2017, 08:57:13 pm
content: CalMachine, if you need comparative measures in the boards of the 3245 for repair, let me know while mines are still open and uncalibrated. 15 days most

author: CalMachine
author_rank: Frequent Contributor
timestamp: September 09, 2017, 09:03:12 pm
content: Quote from: MasterTech on September 09, 2017, 08:57:13 pmWill doThank you much! The 3245 won't be in my possession until Tuesday, though.

author: PartialDischarge
author_rank: Super Contributor
timestamp: September 13, 2017, 04:49:45 pm
content: Just cleaned all dust inside, installed the nvrams in sockets and changed filters for new ones with surge protection, a bit longer than the originals but there's still room. These units are pretty nice except for the display that has gone down in luminosity albeit still perfectly visible.

author: Zucca
author_rank: Unknown
timestamp: October 17, 2017, 02:06:11 pm
content: Boom!One more in the club!I just got a HP 3245A with High Voltage OPT for 866,49 EUR delivered. TEA TEA TEA. List price was 1200€eBay auction: #192335067589Oh well, so crazy!Now I have to get a HP3458A....

author: nikonoid
author_rank: Regular Contributor
timestamp: October 17, 2017, 02:33:49 pm
content: Nice! Congrats! I also got 3245a with high voltage option. It got mechanical damage in shipping, so it was only $140. I will put repair photos here, when I get to do the repair.Any recommendations for replacement EMI filter brand/type for 3245a and 3458a? Does it make any difference? Thanks.Sent from my iPhone using Tapatalk

author: Zucca
author_rank: Unknown
timestamp: October 17, 2017, 02:39:11 pm
content: Very well!Well I hope the transport damage didn't compromise the circuity inside.What $140? It was a XMAS present to you?And of course everybody will now post they got a 3245A for almost nothing...Let´s keep in touch! Well I need to finish some more project before to restore this puppy.

author: nikonoid
author_rank: Regular Contributor
timestamp: October 19, 2017, 03:12:10 am
content: I guess I just got "lucky" with damage. I reseated a cable and got it to work. It is a bit out of spec but otherwise. If I was to get all damaged mechanical parts from keysight it will be about $400-$500, making it a bit less of a good deal.I am fairly handy and have right tools. I am planning to do some sheet metal work and attempt to glue plastic before paying money to Keysight.I am also planning to change emi filter, fan, and electrolytics.In a same boat with you, I also need to finish few things before starting this one. Let's definitely start at in touch.Sent from my iPhone using Tapatalk

author: PartialDischarge
author_rank: Super Contributor
timestamp: October 19, 2017, 05:58:02 am
content: Quote from: nikonoid on October 17, 2017, 02:33:49 pmAnyone you like, I hope schaffner has learned from the past by now, I used this one from mouser FN9222UZ-3-06 with surge protection, cause I live in a thunderstorm-prone area.

author: View[+]Finder
author_rank: Unknown
timestamp: November 24, 2017, 11:14:00 pm
content: Based on the excellent writeup and video by TiN xdevs, I found a used HP3245A on eBay (where else?) for about the same $$ as was mentioned in the post. It arrived in better physical condition than expected, but was way out of calibration. Having to calibrate the old way with a DMM and manual input of voltage makes one appreciate the value-added in the 3458A calibration method. After my usual internal inspection and dust removal (no IPA this time) the 3245 was ready for warm-up and calibration.The end result is that my 3245A has passed all the 'tests' and is in line with all the performance measures. One troublsome spot--perhaps due to the state of earlier cals (there had been 14)--there was a glitch related to Step 45. My first time the 'voltage' indicated -.004 so that's what I entered, but after that Step 46 and 47 were out of line with the example in the book and the calibration was not accepted. (What a PITA: I can go for coffee while the 3458 chugs along on the volts cal)Without wasting too much time on precision, I started another cal and used the 'book value' for Step 45. It worked, but not as well as possible. My next cal was done with care on volts only and I recorded the entries on paper. I used .0001 for the Step 45 in lieu of the slightly negative 'suggestion' from the 3245, just wanting to see if that would give better results. It did; much better.The final was a full cal and all voltages were fed to the 3458 (NPLC 200) and to my 34465 DMM set up to collect a histogram of readings at 1 PLC. Both meters were reading the same voltage from the 3245 and the 34465 was set on 'High Z' so as not to load things down. Each run of the histograms captured over 1000 obs and sometime several times that. By observation, each histogram was checked for skewness, kurtosis and bi-modality and restarted if needed. With a stable and reliable histogram, the consistency of mean and standard deviation were used to indicate the end of the run. The mean value of voltage was used as the input to the 'CAL VALUE' on the 3245. This was usually close to the value displayed on the 3458, but when different, the 34465 'mean' was used. Current calibration was done with the 34465 alone using the same process as above.The 'histogram' method improved a bit on the 'straight from 3458' as suggested in the 3245 cal manual. Performance results that were near the edge of the range were now close to the center in all cases.

author: View[+]Finder
author_rank: Unknown
timestamp: November 26, 2017, 11:35:56 pm
content: Has anyone done any investigation /experimentation around the 3245's frequency generator? There doesn't seem to be any way to calibrate, so I assume there is a crystal oscillator running the show. For example at 300kHz dialed in on the 3245 and measured on a HP5316B counter (with 10kHz Rh reference) it shows 300.0035E3. The 3458A shows the same. On the o'scope there seems to be an occasional glitch maybe from a higher frequency.Not a big deal, but if anyone has more info . . ..Probably well within the specs for an instrument of that age.Thanks

author: Samogon
author_rank: Frequent Contributor
timestamp: April 20, 2018, 02:53:20 pm
content: Are you accepting new members?I have got 3245A with startup error "92 Bus Source issue"Measured all voltages on A6 (PSU) all voltages are good except 15V at J15 shows 21V. Measured P2 connector pins 1 and 2 give 17VAC as i understand transformer output too high. In order to have 15VDC after bridge rectifier and filter capacitor we need to have 10VAC input.Line set to 120VAC. And what i suppose to think? Transformer? This unregulated 21V goes to backplane A2 and there distributed to source A1. I thinking to place voltage regulator between A6 (PSU J15) and A2(Back plane).What do you think?BTW i have supplied 15V to A2 from lab supply and it did not fix an error. So i assume A1 is damaged.

author: TiN
author_rank: Super Contributor
timestamp: April 21, 2018, 03:54:10 am
content: Isolated voltages on A1 generated by separate switching supply, so higher input voltage does not matter much I think.Check BP error signal generation circuitry on backplane.IMG

author: Samogon
author_rank: Frequent Contributor
timestamp: April 22, 2018, 03:38:27 am
content: Ok removed both source cards and here we are BBQInstalled only CH1 card and we are alive, no errors, selftest passed.So at least i have one good card and one toasted, this is much easier to repair since they are identical, so i even can do offline component comparison.Not bad outcome.

author: TiN
author_rank: Super Contributor
timestamp: April 22, 2018, 03:50:26 am
content: Sweet, now pimp it with LTZ!

author: nikonoid
author_rank: Regular Contributor
timestamp: April 22, 2018, 04:15:59 am
content: Samogon, congrats on having one channel working. Second should be fairly easy.I have the 3245a version with 10x output (100V).Even without LTZ mine is fairly good at 10V (give or take few ppm). Now 10x output is off by quite a bit +28ppm. I cannot find a way to adjust that. The zero for 10x output is adjustable with a cal pot on a side.Would anyone know if there a good way to adjust magnitude of 10x output?

author: Samogon
author_rank: Frequent Contributor
timestamp: April 22, 2018, 05:49:46 am
content: I have Fluke 732A on the way, so i dont see reasons except curiosity for LTZ. I rather would like to get x10 card. If i get x10 i would get rid of Tek TM506 with TG506 sinse i need 50V square wave 1kHz

author: Samogon
author_rank: Frequent Contributor
timestamp: April 22, 2018, 06:45:10 am
content: So far i have found K3 relay is stuck in open not latched, and mosfet Q901 short as i expected due to our burnt friend C900.Something catastrophic happened.

author: Samogon
author_rank: Frequent Contributor
timestamp: April 28, 2018, 05:24:57 am
content: OK, it has been fixed.1. As i said Q901 was dead short, replaced both Q900 and Q901 (BUZ71A) as they make pair so to be sure that i have close parameters i used IRFZ20PBF2. Blown linear regulator U906 (LM7915) replaced with same3. Charred C900 470uF 25V changed4. And fuse which blown after all components listed above went kaboom. Well at least it prevented more catastrophic consequences.So need to order to replace Puffner filter and calibrate this nice peace of equipment.But 10V is too low i will be locking for unit with option #2 or amplifier board itself. If some one has a lead i would appreciate.

author: Samogon
author_rank: Frequent Contributor
timestamp: May 02, 2018, 04:58:31 pm
content: About K3 relay, stupid me, it did stuck in wrong position, but what i have expected from latching relay. Once power rails were restored, firmware run initialization sequence and it K3 into proper position. Well, now i have spare relay for $20

author: rastro
author_rank: Frequent Contributor
timestamp: September 28, 2019, 12:01:55 am
content: Has anyone found a replacement source/part for C900 on the source boards. This is the 470uF/25V radial electrolytic with an additional ground lead (screen?) at the top?

author: JesseLackey
author_rank: Newbie
timestamp: March 12, 2020, 12:09:46 am
content: If you're going to dig in, why not do 3?(see attached pic... not sure it shows up inline in the post, I'm a newbie here)Been scouring this thread and the excellent writeup at <https://xdevs.com/fix/hp3245a/>Hopefully somebody out there is still interested in these beasts, I'd enjoy any commentary and help. For sure I'll need to replace the NVRAMs.I don't have an HP 3458A, but I do have a calibrated Advantest R6581T for DC V/I. And USB->GPIB coming soon.Cheers all!J

author: JesseLackey
author_rank: Newbie
timestamp: March 12, 2020, 06:29:32 pm
content: ...and first questions, if anyone has some general tips...1. the Schaffner is riveted (?) to the frame, at two points. I don't need to rivet in the Delta 06geeg3e replacement (or maybe just a new Schaffner), but ... how should I remove it? Is this a drill-out-the-rivet job? I've never had to deal with this before.2. opening up the 1st of the three, everything looks really pretty good, a little dust is all. The only date codes I can find are on the EPROMs, 8849 and 8850, meaning the 49th and 50th week of 1988, one assumes. Is there a date code anywhere else? I wonder if the date code is not necessarily when the EPROM was programmed but the revision of the firmware. Seems unlikely tho. Thoughts?3. The electrolytics all look just fine. I'm going to spot check ESR on 2-3 largest ones, if the ESR looks ok, should I replace anyway? Opinions?From the date code, and somebody's post here about list price in 1988, the one I'm working on (it has option 1, two channel output) cost nearly $7000, which is nearly half the tuition for my sophomore year at Cornell!Thanks all!J

author: Samogon
author_rank: Frequent Contributor
timestamp: March 12, 2020, 06:47:50 pm
content: I have drilled out rivets with drill bit bigger than rivet heads diameter. Punch pivoting hole in the center of the rivet head.First if all make complete self test, get service manual and CLIPSo that is fir the start

author: rastro
author_rank: Frequent Contributor
timestamp: March 12, 2020, 09:24:52 pm
content: Quote from: MasterTech on March 12, 2020, 08:31:19 pmThe unit with the "ERR 92" most likely has the C900 bad on one of the driver PCB's.

author: JesseLackey
author_rank: Newbie
timestamp: March 13, 2020, 07:52:13 pm
content: Hi all, thanks for the tips, I'm going to replace C900 and all the other electrolytics besides. I'm making the shopping list now.I have all the docs for the 3245A, including the very useful CLIP.I have a dumb newbie problem. I can't pull the pcb shown below from the backplane, I've removed all 7 screws and it moves a few mm but then it seems like it is latched in place or something like that.I've used a fair amount of force. I want to make sure I'm not missing something before I pull harder.Image below.Any thoughts greatly appreciated.J

author: PartialDischarge
author_rank: Super Contributor
timestamp: March 13, 2020, 11:28:06 pm
content: There is a screw on the side that relases the metal plate over which both boards are mounted.Also buy some green through hole fuses that that board has near the connector, cause they may be blown

author: rastro
author_rank: Frequent Contributor
timestamp: March 14, 2020, 03:01:41 pm
content: The PCB's are a pain to remove - lot of jiggle and sliding. There should be a procedure in the manuals as I recall. Check for PDF's on line.I had the C900 go bad. You definitely need to order the solder in fuses - most likely blown.

author: PartialDischarge
author_rank: Super Contributor
timestamp: March 14, 2020, 05:28:42 pm
content: Quote from: rastro on March 14, 2020, 03:01:41 pmThey are pretty easy actually, the trick is to remove the lateral screws that hold the metal plate. Then this metal plates shifts both upper and lower boards out of the connector

author: JesseLackey
author_rank: Newbie
timestamp: March 14, 2020, 09:53:57 pm
content: So nice to have your help rastro and mastertech! I was able to remove the boards, I'm not sure removing the metal plate was actually necessary but it allowed everything to be more jiggle-able and it was then easy.I'm taking apart the working unit of the 3 so all fuses are fine (I continuity checked just to be sure), but that is a great tip, I'll get some for the other two units.Any thoughts on the DS1235YW-150? I'm going to need 6; octopart.com comes up with only 2 places with the full part number.Is there a recommended (by eevblog people, not Maxim, where you can't even get the datasheet it looks like) replacement?<https://www.maximintegrated.com/en/design/technical-documents/app-notes/2/202.html> has some good info I'm looking at.also: <https://www.avsforum.com/forum/16-crt-projectors/246228-what-replace-dallas-ds1235yw-150-a.html>I'm about to buy a power duster too, the "metrovac datavac" was recommended in a post on eevblog, but the "Compucleaner 2.0" is substantially cheaper and has good amazon reviews. My air in a can is now just an empty can and I decided no more cans.Tx all!JUpdate: from the maxim appnote referenced above:"What's a DS1235?A number of years ago, Dallas Semiconductor® had a 256kb NV SRAM product called the DS1235. It was functionally and physically identical to the DS1230, with the exception that the DS1235 had a five-year data-retention expectation instead of 10 years. An alternative is the DS1230 with the same power-supply tolerance, and with a performance rating equal to or faster than the original DS1235 product (for example, the DS1235Y-150 should be replaced by a DS1230Y-70+)."So there we have it!J

author: JesseLackey
author_rank: Newbie
timestamp: May 08, 2020, 10:40:40 pm
content: Hi Alan, firstly thank you so much for all your info regarding the HP 3245A. It gave me confidence to buy & work on rebuilding/repairing no less than 3 of them (simultaneously!)I just today got GPIB going with a new NI USB<->GPIB converter, and your calibration app (V0.2) was able to see the HP 3245A. A great first step.I'm about to order a GPIB "splitter" so that I can talk to the HP 3245A and a HP 34401A simultaneously. I don't have a HP 3478 but the 34401A can emulate it, apparently nearly completely.(I do have an Avantest R6581T w/NIST cal, but it is DC V/I only, no AC).2 questions for you ...Is there a more recent version of your app? The 0.2 was the latest on your site.Are you willing to share source code? Being able to tweak it could be very helpful; I have visual studio and long experience with C/C++ and a little with python. I assume this is C. Modifying it to use my R6581T for the DCV/DCI portion would be pretty fun... and having code like this is a great starting point for further GPIB adventures.Many thanks in advance!J

author: Omicron
author_rank: Regular Contributor
timestamp: December 23, 2021, 07:01:57 pm
content: Quote from: rastro on September 28, 2019, 12:01:55 amDid anyone find a good replacement for this cap? Is the 3rd lead just there as a mechanical support or is it indeed used for a screen?

author: Samogon
author_rank: Frequent Contributor
timestamp: December 23, 2021, 07:08:01 pm
content: I just used regular radial capacitor, bent connector and glued to PCB with 704 silicon rubber glue.

author: Omicron
author_rank: Regular Contributor
timestamp: December 24, 2021, 08:25:48 am
content: It seems the original capacitor is from this series from Vishay:https://www.vishay.com/docs/42054/672d.pdfAccording to this the third terminal is not connected (see page 2). It seems it has a rating of 2.35A ripple from 20KHz to 100KHz and an ESR of 0.22 to 0.08 ohms. So I wouldn't replace it with just any generic 470uF capacitor. I think I will be using this one:https://www.digikey.be/en/products/detail/panasonic-electronic-components/EEU-FR1H561B/3072260I'm taking a higher value because the original is specced at -10% to +100% and the replacement is +-20%.

author: drhex
author_rank: Regular Contributor
timestamp: December 12, 2024, 10:34:24 am
content: 3245A incoming, does anybody have a BOM for recapping?