hybridfree/eevblog-posts huggingface dataset:
HP 53131A - dead power supply - Page 1
Forum section: electronics / repair

author: fchk
author_rank: Frequent Contributor
timestamp: June 07, 2020, 09:56:36 am
content: Hi,I've got an HP 53131A Universal Counter with a dead power supply. Does anybody has schematics for the power supply? The service Manual only has schematics for the mainboard. Are there common failures known?There are two fuses, but both are ok. Capacitors look ok at first glance, but a a whole re-cap would be my first guess.Can I run the power supply without load?Any recommendations?fchk

author: George Edmonds
author_rank: Frequent Contributor
timestamp: June 07, 2020, 11:48:11 am
content: HiThe power supply is a third party item and there are no power supply schematics in the CLIP.Be very careful as it is always on to power the OCXO with a soft power switch for the counter itself.It is of the "flyback" type and will readily self destruct, it may need a small minimum load.George G6HIG

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: June 07, 2020, 01:22:38 pm
content: Someone from the forum reverse engineered the ps here:https://www.eevblog.com/forum/repair/agilent-53132a-repair-(and-possible-upgrade)/msg841547/#msg841547

author: DeepLink
author_rank: Regular Contributor
timestamp: June 07, 2020, 07:55:54 pm
content: Use some resistors as load ~10% of rated load is sufficient to have proper regulationLook at the start up resistor R2, can be openAnd do exchange all the caps (mine was leaking badly - even though the PSU was working)Use proper SMPS caps - low esr, high ripple currentAs the PSU is always on (and the fan is always running), it is possible to make a mod that shut down the PSU/FanThe fan can be upgrade to a low noise, as the original is quite loud

author: Decee1
author_rank: Regular Contributor
timestamp: March 04, 2022, 04:36:11 pm
content: Hello,I've just finished repairing my power supply and i thought i would leave some information about the fault.Fault description:No voltage on secoundary side, cannot measure any pulses on IC1 pin 6(out) but IC1 pin 4(RT/CT) is available and running with sawtooth wave.Fault conclusion:Q22 is acting like a short but is still fully functional. In my case it measured 1V on collector and emitter and 0.5V on base.Measurements:if pulses is not on IC1's output, RT/CT is active and there are no voltage on comp pin IC1 does as expected and therefor Q24 pulls IC1 pin 1 (comp) down to GND, then measure base of Q23 or R20, then it is measuring around 0.7V or above which turns on Q23, If Q22 measures the same voltage across it, the Q22 is faulty and should be replacedFault explained:Q23 is 'on' which causes Q24 to 'turn on', pulls down the internal current source of IC1 pin 1(comp) and therefore 0V on IC1 pin 1(COMP) pin and no switching pulses on IC1 pin 6(out)Hope my debugging can be useful for somebody else.
HP 53131A has dissolved rubber on board, How to clean? - Page 1
Forum section: electronics / repair

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: February 06, 2024, 11:11:03 pm
content: Hi, I just got a parts unit 53131A that was missing the power supply. I have a spare supply so I hoped I could get it working.However the main board is covered in goop around the area that the rubber spacer of the power supply sat above.Also on the bottom the area around where another spacer sat is covered with residue.Looks like both spacers liquified and spread over the board!I stuck probes onto the black goo on the top and it has a resistance of around 5 giga-Ohm. (1/8" spacing banana jacks)Wondered if I could try powering it up as is or would I be safer to somehow clean off the goop!Any suggestions on how to safely get it off without damaging anything???Cheers,Corby

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 07, 2024, 12:25:22 am
content: That's looking rather...interestingon the top there.... I had the same with the rubber pad on the bottom. Isopropyl alcohol will clean it right up.The melted rubber won't cause any short circuit etc, but best not to leave it there.Also, if you have the means for recalibration, and a firmware earlier than version 3944, you can upgrade it,firmware images here.If you have a firmware other than 3643 or 3944 and a chip programmer, please do share!

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: February 07, 2024, 11:19:43 pm
content: Well I reassembled it without cleaning the board and installed the new power supply.It comes up just fine and is working great!I'll just say it's conformal coating!How do I tell what firmware it has?Cheers,Corby

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 08, 2024, 01:29:14 am
content: The firmware version can be displayed by holding down the 'recall' button and turning the unit on, also you can check the stickers on the 4 ROM chips.It might be worth updating if you can, there were known bugs in the earlier firmwares.If you are lucky, you'll have EEPROM chips (My 53132A did) so you can just flash the new firmware onto them, if you have one time programmable EPROM chips (like my 53181A had) you'll need to get new chips to program the new firmware into.For reference, the EEPROM chips in my 53132A are 28F010 and the OTP EPROM's in the 53181A are 27C010, both in PLCC 32 packages. Any equivalent with -150 or lower number for the speed rating should work fine.Be careful leaving the goop there, it may or may not end up corrosive...
HP 53131a repair help - Page 1
Forum section: electronics / repair

author: 705jas
author_rank: Contributor
timestamp: January 21, 2025, 01:59:08 am
content: Hi AllI had intermittent FR FAIL errors on startup. Ch2 & Ch3 seem fine. Only Ch1 does not work. I thought I had tracked it to the K7 relay as a tap on top of it resolved the issue temporarily. I ordered some new G5Y-1-DC5 relays (the closest I could get) and installed one. Still the same issue. No triggering on Ch1 at all unless I short Pins 1&7 on the K7 and then it triggers but gives random readings. The new relay has continuity from Pin 1 to 4 but not one to 7 if no power on 7. If power is on with 5v on 7 you get continuity from 7 to one which I think is how it should be. That is testing the K7 out of the unit.When I put it in the unit and power it I get continuity between 1 and 4 still but nothing between 1 and 7. I do seem to have around 4.6v on pin 7 all the time though. Any help is appreciated.cheers...Allan

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 21, 2025, 07:52:41 am
content: Is the relay actuating when in the 53131A? If not, or if not actuating reliably, I'd be looking at the relay drive circuitry. IIRC there is a buffer or some such thing driving the relays?
HP 5315A wont count - Page 1
Forum section: electronics / repair

author: Daxxin
author_rank: Regular Contributor
timestamp: April 25, 2017, 12:02:14 pm
content: Power on test looks fine exit with all 3 zeros but from that status wont give any sign of lifeeven apply input channel signal.following the signal 10Mhz from sine generator looks like comparator chip is faulty if someone can confirmchip 1826-0426 AM68TADL (cannot find any datasheet ...equivalent?)

author: Dr. Frank
author_rank: Super Contributor
timestamp: April 25, 2017, 12:32:44 pm
content: What about the trigger level on pin 8?Is it possible to change this?Maybe the voltage on this pin is way off, due to another defect, i.e. constantly @ +5V or -5.2V.Are the supply pins 6, 11 correctly fed?Are all supply voltages present? I see some tantalum caps, which also could have failed.What about channel B, is it functional, instead?Frank

author: Daxxin
author_rank: Regular Contributor
timestamp: April 25, 2017, 12:51:43 pm
content: Quote from: Dr. Frank on April 25, 2017, 12:32:44 pmfeeds is correct , common button trigger/sensivity , in trigger mode turning the knob i get from -2.54v to +2.54vin sensivity mode from -0.041v to +0.066vexpecting square waveform on comparator output ..im right?

author: Dr. Frank
author_rank: Super Contributor
timestamp: April 25, 2017, 01:22:19 pm
content: Yes, I'd expect complementary square waves on both outputs (180°).Anyhow, if you apply the signal to channel B, you should see either this correct output (square wave), or also noise, like on channel A.This would indicate, if the whole IC is dead, or the upper OpAmp only.As a replacement, you'll need a double fast comparator.This one might be an ECL line driver, which might not be available anymore, as of today.Frank

author: Daxxin
author_rank: Regular Contributor
timestamp: April 25, 2017, 01:26:03 pm
content: Quote from: Dr. Frank on April 25, 2017, 01:22:19 pmOK thanks for helping Dr.Frank both sides dead i m checking MAX912 datasheet as replacement it looks very fine

author: Dr. Frank
author_rank: Super Contributor
timestamp: April 25, 2017, 02:00:33 pm
content: This MAX912 has a TTL output, which will probably not work.My guess was correct, see page 8-9, or 83/106 in the manual- the comparators have ECL outputs, which usually means negative output signals.PS: maxim still offers ECL comparators, like the max9693.I checked pinning, this type is more suitable, and it's also fast enough for > 100MHz.Frank

author: lowimpedance
author_rank: Super Contributor
timestamp: April 26, 2017, 06:56:09 am
content: Quote from: Daxxin on April 25, 2017, 12:02:14 pmThe part number is AM687ADL no Tdatasheet herehttp://www.datasheets360.com/part/detail/am687adl/961240802637534603/?alternatePartManufacturerId=0And the MAX9693 that Dr. Frank found looks like an excellent replacement.

author: andymok
author_rank: Contributor
timestamp: August 08, 2021, 03:30:19 pm
content: Hello From Hong Kong.I have a HP 5315A and I’m experiencing exactly the same thing as you described. How was your unit? Did you find the fix?Much appreciated!
HP 5316B channel C issue - Page 1
Forum section: electronics / repair

author: gossamer
author_rank: Contributor
timestamp: October 05, 2021, 04:09:35 pm
content: Channel C on my unit doesnt work. So I started through the troubleshooting part of the service manual.point 8-118 is fine, all voltages are present and correct.8-119 is where it shows something is not right. So, Ive set the signal gen, 100Mhz, 280mVpp, 50Ohm output.C1 measures 240mVpp and 100Mhz, at 0V offset. C2 measures the same. C3 signal is offset by 2.3v and measures the 100Mhz and 240mVpp. Now the manual shows (blurry scanned service manual, so hard to say), but signal looks the same as C1 and C2.C4 I cant see anything apart from some high freq noise.What I dont know now is whether U1 output is correct or not?
HP-5323A - Page 1
Forum section: electronics / repair

author: W3SLK
author_rank: Contributor
timestamp: September 28, 2025, 05:10:23 pm
content: Along with a 8660C that I have since repaired the RPG in it and a 3586C with a bad 03586-66580 pcb, (but thanks to Bob Weiss,N2IXK for selling me a 're-manufactured' pcb), I also got a very clean 5323A frequency counter that uses the nixie tubes. In fact it is so clean it is missing A16, the 05323-60022 power supply pcb. Looking on the internet, finding a spare seems to be like looking for 'hen's teeth'! Did this board have a common failure associated with it? There doesn't look to be too much other than 2 regulating systems for +175VDC and +5.1VDC. If I can't find anything this unit will become a 'hanger-bay queen' for the masses.

author: factory
author_rank: Super Contributor
timestamp: September 28, 2025, 07:14:39 pm
content: The board is also used in the 5325 and at least one other thing here (total of 5 that all work fine), shouldn't be too hard to have a new board made, it's not that hard.David

author: W3SLK
author_rank: Contributor
timestamp: September 28, 2025, 11:30:19 pm
content: David said:QuoteYes, but having no access to board stock that kind of makes it a little more difficult. At least with your photo I know what I am looking for to stuff in there. Searching the internet, doesn't come up with much though.

author: factory
author_rank: Super Contributor
timestamp: October 04, 2025, 01:01:38 pm
content: Here is some more info, the parts list, circuit diagram & board layout for the 05323-60022*, the -12V supply from the other board is used by the +5.1V regulator. I'm not able to scan the whole manual, don't have enough time, nor do I want to ruin the binding.*note there is an earlier version of this board 05325-60039, used in earlier revisions of the 5323/5325Parts for the 175V supply;CR11 is 1902-3429 Zener 100V 2%,CR12 is 1902-3394 Zener 75V 2%,Q2 is 1854-0232 NPN (aka 2N3440, 2N3440A, this is a RCA 40327 on one of mine).Q3 is 1854-0071 NPN (can be 2N3704, note odd ECB pinout with leads formed to EBC layout for some original parts. Or use 2N3904 which has EBC pinout)An for the 5.1V supply:CR10 is 1902-3094 Zener 5.11V 2%,Q1 is 1853-0020 PNP (can be 2N3702, again note ECB pinout & formed to EBC layout. Or use 2N3906 EBC pinout).P.S. There is a thread running in parallel over on antique radios, might be helpful to add a link to the info here, I really should join that forum;https://antiqueradios.com/forums/viewtopic.php?t=451405David

author: W3SLK
author_rank: Contributor
timestamp: October 06, 2025, 11:16:10 pm
content: factory said:QuoteYes, I started that thread. I got a lot of help from over there but sometimes I like to use as many resources as available.I downloaded those sheets and have now made them a part of my manual. Mucho gracias!
HP 5335A GPIB commands - Page 1
Forum section: electronics / repair

author: grendle373
author_rank: Contributor
timestamp: April 14, 2025, 05:22:41 pm
content: Hi, I have a hp 5335A, Im trying to verify the fast gate and Ratio a-b commands over Gpib. Can anyone help with some simple commands to try? I have NI software as well as HT Basic but I'm not savvy on the programming / Gpib end. Any help would be great! Thanks in advance!

author: pqass
author_rank: Super Contributor
timestamp: April 14, 2025, 06:31:10 pm
content: See the5335A manualpage 3-36 for the full list of commands.Try sending "FN5" to switch function to RATIO A/B, "RE" to RESET, or "DR1, DI12345" to display 12345 on the display.I can't help you with what NI software you'd use to interactively send these commands or whether you need to make a program to do so.The way I interact with my 5334A is via serial terminal program (GTKTerm) to myAR488 controller.

author: grendle373
author_rank: Contributor
timestamp: April 14, 2025, 07:42:46 pm
content: Thanks! Going from the manual, The unit responds to the reset RE command, but the display just goes blank with the DR1 DI 12345 command, as well as FN1, FN5. thinking it has to be an issue in the gpib interface board. No issues with the unit manually from the front panel.

author: grendle373
author_rank: Contributor
timestamp: April 16, 2025, 06:39:37 pm
content: Thanks! got it fixed. Bad caps on the gpib board. GM1 sets fast mode, although I need to follow up with a RE command. The unit then resets for the new measurement with fast mode enabled, IN resets to defaults.
HP 5342A ERROR MESSAGE #2 ( A14 U4 Fail ) - Page 1
Forum section: electronics / repair

author: HAF_RIO
author_rank: Newbie
timestamp: January 03, 2022, 02:54:18 pm
content: Hi,I have the HP 5342A with error message #2, and the service manual is informing A14 U4 fail.So, the instrument is in inoperative condition!I checked this mask rom is type 8316.I would like to ask if someone could inform the best way to replace it.I have the U4 binary file, for the old CPU board, as mine.I saw some article on the web about use some type of replacement more easy to find, but I have to many doubts.Thanks in advance,Helcio
HP 5347A Fails HP-IB Test - Page 1
Forum section: electronics / repair

author: mbielman
author_rank: Contributor
timestamp: February 07, 2020, 09:37:34 pm
content: Hello. I repaired an HP 5347A (20GHz freq counter) and this unit did not have the HP-IB interface option. I found one, installed it, and it fails the HP-IB power on self test. Installed a known good interface card and still fails. Continuity from the motherboard is good and the 5V supplies are fine. There are no option jumpers anywhere that I can find and the manuals make no mention of this... just install the card and that's it.Wondering if I have a firmware rev issue or some such thing.Anyone have experience with this?Appreciate the help.Thanks.Mark B

author: jfphp
author_rank: Regular Contributor
timestamp: February 08, 2020, 10:35:30 am
content: You have probably to enable the option in the configuration EEPROM on the CPU or, if no EEPROM, to change the firmware in the EPROMs

author: mbielman
author_rank: Contributor
timestamp: February 08, 2020, 04:00:02 pm
content: There is no EEPROM and no config menu or settings to alter. This is what I do know:The EPROM on the CPU board has the proper HP part# and the service manual has no comments regarding versions so suspect it is the right code.The unit has a "IB SENSE" line that gets pulled low when the card is installed so the system knows if it has HP-IB or not.Power supplies, RESET signal and interconnect continuity are all good, and it is a known-good interface card.The data and control lines are connected directly to the CPU (6803).A bit stumped.Mark

author: mbielman
author_rank: Contributor
timestamp: February 08, 2020, 07:18:31 pm
content: FIXED IT! Someone had replaced one of the connectors on the MB to the CPU board and apparently destroyed two of the connections that control the HP-IB interface. (!)Added two jumper wires and it works. Another unit saved!!!Mark

author: Tony_G
author_rank: Super Contributor
timestamp: February 08, 2020, 10:49:49 pm
content: Nice - Congrats.TonyG
HP 5350B 10MHz output strange waveform shape - Page 1
Forum section: electronics / repair

author: matthuszagh
author_rank: Frequent Contributor
timestamp: December 30, 2020, 06:16:11 pm
content: I connected the 10MHz output of my HP 5350B microwave frequency counter to the input of my oscilloscope via a BNC cable and I was surprised by the waveform shape. I've attached an image showing this (the yellow trace is the HP 5350B 10MHz output and the green trace is a 10MHz standard from a GPSDO). Is this normal? I would have expected a sine wave. The 5350B is equipped with a high-stability oven timebase (option 010). I did some quick tests of the 5350 and it seems to work as well as I'd expect for a used Ebay item. I hooked it up to my HP 8341B (this is not calibrated, so the frequency is probably a bit off) and it read out close to the correct frequencies to the signals I gave it (it was always about 500Hz high, IIRC). The inside of the device appears to be in good shape. I also checked the 1MHz output which appears as a square wave with a fair amount of ringing on the edges. I can post an image of this if it's useful. Because I used a BNC cable directly I don't think this should be the result of the way I'm probing the signal (e.g., because of a long ground lead causing inductance).

author: jfphp
author_rank: Regular Contributor
timestamp: December 30, 2020, 06:45:31 pm
content: Did you put a 50 Ohms feedthrough before the scope input ?

author: matthuszagh
author_rank: Frequent Contributor
timestamp: December 30, 2020, 06:52:36 pm
content: Quote from: jfphp on December 30, 2020, 06:45:31 pmWell, I feel stupid. Changing my scope input impedance to 50ohm yields a waveform that looks much better.

author: jfphp
author_rank: Regular Contributor
timestamp: January 02, 2021, 11:52:43 am
content: What is the high stab reference ? HP 10811X ? Does your mesurement take place directly at the oscillateur output or is there a circuitry between. In the last case make direct connection to the oscillator output.Apparently there is something wrong : shape and offset.

author: matthuszagh
author_rank: Frequent Contributor
timestamp: January 04, 2021, 12:32:54 am
content: Quote from: jfphp on January 02, 2021, 11:52:43 amYes, it's a 10811. I've connected the BNC cable assembly to the back panel 10MHz BNC connector. Is this not the correct way to do it?

author: jfphp
author_rank: Regular Contributor
timestamp: January 04, 2021, 11:13:58 am
content: 10811A floating through rubber O rings and connected by soldered wires and coax or plugged into a connector soldered on the mother board ?

author: jfphp
author_rank: Regular Contributor
timestamp: January 04, 2021, 11:40:03 am
content: We are vasting our time : take the op and srvce manual (05350-90021) : you will see p 8.43 block diagram that the 10 Mhz out comes not direcly from the 10811A but from the time base buffer part of A1 throogh line drivers and compare your waveform(s) with those displayed on the various sheets . 10 Mhz comes from U9C pin 10 and cannot be a sinusoidal waveform !
HP 5351A failure HPIB - Page 1
Forum section: electronics / repair

author: hnjmkl
author_rank: Regular Contributor
timestamp: April 23, 2020, 07:04:24 pm
content: My 5351A from HPIB failure, mounts a Mostek MK38P70 with EPROM 2532 on it, I ask which way to go to try a solution, I have no problems reading and writing EPROM.
HP 5381A service manual sought. - Page 1
Forum section: electronics / repair

author: Paceguy
author_rank: Regular Contributor
timestamp: November 10, 2024, 02:27:19 pm
content: I'm looking for a copy (pdf) of the service manual for my hp 5381A frequency counter. Someone changed the caps in the power supply and I'm not sure that they used the right values. Thanks in advance!

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 10, 2024, 02:31:31 pm
content: Artek Manuals has it:http://artekmanuals.com/manuals/hp-manuals/

author: Gertjan
author_rank: Frequent Contributor
timestamp: November 10, 2024, 04:22:33 pm
content: When I Google "hp 5381a manual", I get multiple hits in the first 10 answers.....
HP 5384A (5385A) Crow-Bar SCR Help - Page 1
Forum section: electronics / repair

author: MitSenf
author_rank: Newbie
timestamp: November 02, 2019, 11:22:15 pm
content: Hi,While installing an OCXO in my HP 5484A, I got a little too handsy and shorted the 5V rail to chassis. This let out the ghosts on SCR CR9 (See attached Schem), the 5V Reg, and possibly the PNP Q10 - no shorts detected, however, hFE measured zero.The service manual list the SCR Mfg P/N as SCR1153K (no google hits) and the part looks to be some custom Motorola job - Markings are (top) R002, (mid) 8, (Bottom) 4-0221. No luck tracking any of these numbers down either.I replaced the SCR with a 2N6507G I had in the parts bucket, as well as the BJT with a MJE2955T (service manual P/N = X45H28I; Modern Equiv. -> D45H5). This appears to have fixed the problem, or at least it allows me turn the thing on without blowing any fuses. Nevertheless, I'm not overly familiar with SCRs/Crowbar Circuits, and replacing them.Will I be okay with this sub on the SCR? Or if not, does anyone have an idea on a proper sub?Also, the PNP BJT I replaced had a gain approximately double that of the 2955T @4A, yet the 5V switch-mode seems to be operating fine. If this is adding more strain than I'm thinking to the switching circuit, then I'd be okay ordering a D45H5.Thanks very much for your help, and I certainly appreciate any input.

author: thinkfat
author_rank: Unknown
timestamp: November 02, 2019, 11:59:07 pm
content: The SCR is likely not so tightly spec'd, just make sure it's able to blow the fuse when it fires. The series resistor will take some of the heat. The one you've chosen looks a bit heavy to me, with its 25A current rating. Gate current also seems rather high, you need to make sure something can deliver that current.CR10 is a zener diode that sets the trip point of the crowbar circuit, plus the gate trigger voltage of the SCR.If you're worried about the BJT, maybe use a TIP42C-Y as replacement.
HP 5386A 3 GHz Frequency Counter - Page 1
Forum section: electronics / repair

author: mojoe
author_rank: Frequent Contributor
timestamp: January 13, 2024, 08:23:06 am
content: I bought this counter used about 15 years ago. When I got it, it didn't power on. I found the DC fuse blown (it also has an AC fuse). I replaced the fuse and it worked just fine.Over the years, I've used the counter infrequently. Once, long ago, the DC fuse blew again, but I was busy with other things, so replaced the fuse and continued using it. I thought that perhaps there was a power surge, or the caps were getting old.Fast forward to yesterday, and I needed the counter again. Now it was blowing the DC fuse often (sometimes on power up, sometimes after hours of use). Time to download the service manual. Don't you love old HP service manuals?I checked all the voltages, and they were well within spec. I even let it run all day while the DMM was logging. Again, well within spec. Next, I checked the obvious, like caps, diodes and the SCR in the crowbar circuit. Eveything looked good. Digging a little further, I was checking voltages in various parts of the board - all looked good. I then checked U15, the 2.5 V reference chip. The 5 V input and 2.5 V output looked fine, but while probing, the DC fuse blew again. Hmmm, curious.Taking a closer look, I found what you see in the picture. It has been like this since manufacture. The entire top side of the board is a ground plane, so it took some heat to solder that ground pin.I'm letting it cook for a while, to make sure, but I think I fixed it. Next, I'll have to adjust the internal TCXO. It's 1.37 Hz highI usually don't use the internal reference, but my GPSDO.
HP 5308A  + 5300B Repair  - Page 1
Forum section: electronics / repair

author: GianniPastorino
author_rank: Newbie
timestamp: February 06, 2023, 10:11:26 pm
content: Hi, I have an HP 5308A frequency meter, which I repaired in part. Fault on the power supply part. Replaced a 2n3906. Now it starts to work, but we have a problem on the B channel.The integrated (IC) U2, part HP 1820-1565 is faulty. Unfortunately, I cannot find this part or even an equivalent.I ask you if you have any news about it.

author: Kim Christensen
author_rank: Super Contributor
timestamp: February 07, 2023, 01:44:35 am
content: It might be a ECL comparator. Maybe a MC10E1651 or equiv... Pinout seems to match.

author: bdunham7
author_rank: Super Contributor
timestamp: February 07, 2023, 01:54:44 am
content: I believe that will be an MC1651L, check the datasheet to see if that seems right. They're available from Rochester if you'd like 23 of them. Or try your luck on eBay, Google, etc--they appear to at least exist out there.https://www.datasheets.com/en/part-details/mc1651l-onsemi-37795823#datasheet

author: GianniPastorino
author_rank: Newbie
timestamp: February 07, 2023, 05:11:00 pm
content: Thank you very much, very happy.

author: factory
author_rank: Super Contributor
timestamp: February 07, 2023, 09:45:19 pm
content: The military part database (NSN) gives it as MC1651L too.https://www.parttarget.com/5962-01-064-9563_5962010649563_MC1651L.htmlDavid
HP 54502A CRT to LCD convertion - Page 1
Forum section: electronics / repair

author: JullRay
author_rank: Newbie
timestamp: January 21, 2024, 06:17:31 pm
content: Hello,I would like to ask if HP 54502A display can be upgraded to LCD display.Thank you for help/advice.Regards.

author: tom66
author_rank: Super Contributor
timestamp: January 22, 2024, 02:26:58 pm
content: I had a 54501A a long time ago, gave it to a friend. When I took it apart, it looked like the internal monitor was a Japanese-sourced unit (possibly Panasonic from memory). It is very likely the signals to this monitor are just something like VGA, so it is probably possible to do so, but you would need to find an LCD panel that fit, some way to get the right supply voltage to it, and fit it into the case.

author: Greybeard
author_rank: Frequent Contributor
timestamp: January 22, 2024, 03:03:20 pm
content: Maybe this helps you:https://hackaday.com/2017/06/01/fpga-rescues-scope-from-the-dumpster/
hp 54503a scope psu recap - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: December 08, 2021, 10:22:34 am
content: Hi all,i have just recapped my scope psu,the service manual states to adjust the 5.2v supplies,if i remember it should be done using a 2 ohm load resistor on the 5.2v rail,i didnt do that with mine,i just reconnected the psu as is,at the time the 2x 1 ohm 25 watt resistors were on order,they have now arrived,although the scope seems to be working fine and calibrated ok and passes all self tests,the question is,how critical is the 5.2v rail setting,and should i go and check/adjust it as the scope seems fine,also what outputs should i see at the rear bnc calibrator outputs,thanks in advance,m3vuv

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 08, 2021, 01:49:33 pm
content: Sounds like everything is fine. The 5 V on many HP units is used to power boards with TTL circuits. I have seen PS in HP units that have over power protection, so that the PS shuts down if there is a fault in one of the boards (usually a failed filter cap). TTL voltages are not horribly critical. However the voltage may be used to trigger an overload.Perhaps the use of the low ohm load on the 5 V supply enables you to see if the PS does not shut off with a proper load, besides adjusting the volts,I did not read the schematic and am just offering an opinion.If this is the case that there is an over power circuit, it is not triggering and everything is fine.I would think the outputs are probably TTL voltages so about 5 volts.

author: m3vuv
author_rank: Super Contributor
timestamp: December 08, 2021, 02:19:09 pm
content: cheers for that,my only remaing issue is it seems the calibrator pigtails are crossed over ie the socket fron the r/h side of the mainboard connects too the l/h rear panel bnc,not sure tho as im not the first person inside this thing,have asked on io groups hp site but no answers,its like they are inverted!,also to do the cals had to invert the bnc cable,ie stuff it in the ac bnc rear bnc and not the dc one.

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: December 08, 2021, 02:57:18 pm
content: No crossing over for the calibration coax. Each cable goes out straight from the board to the back panel.

author: m3vuv
author_rank: Super Contributor
timestamp: December 08, 2021, 07:51:37 pm
content: that makes sense as it wont self calibrate unless i invert the cables.looks like someone has been in this before and swapped the pigtails.
HP 54504 A - Gain Chan 1 Calibration error - Page 1
Forum section: electronics / repair

author: Disciple
author_rank: Newbie
timestamp: January 25, 2021, 10:01:37 am
content: Greetings Gentlemen,I have an issue with my HP54504A. When I do the self calibration operation for channel 1 I get the error : Failed Gain Cal Chan 1 0000 0000 0010 0000. All other calibration test are passed with success. The calibration is passed with sucess for channel 2.When I go to the service menu, I have for Chan 1 gain the 0020H error code.I search a clue on the service manual but I found nothing. Do you have any idea where I can start to search ?Thank a lot for your help,Disciple

author: Runco990
author_rank: Frequent Contributor
timestamp: January 25, 2021, 07:45:24 pm
content: The input attenuator may be damaged or just dirty. Try cleaning it or swap around to see if the problem moves. You DON'T want it to be a custom IC. There is some talk about the input attenuators, in particular the 50ohm switch. Swap them first, PITA I know.

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: January 27, 2021, 07:29:52 pm
content: Set Chan 1 50 ohm input impedance to ON. then, measure the input resistance. If higher than 50 ohms, likely the relays are problematic, possibly a damaged or open 50 ohm resistor... Sometimes switching them from 1meg to 50 ohms repeatedly may temporarily clear a relay problem. Then try a reCal to see what happens.

author: Runco990
author_rank: Frequent Contributor
timestamp: January 28, 2021, 12:36:00 am
content: Quote from: SoundTech-LG on January 27, 2021, 07:29:52 pmThat's good advice. And simple. The relays don't get switched much. A Tektronix tech told me they take the problem attenuators and "buzz" them for an hour to self clean the contacts.However, they had a special setup for that.On the HP scope... yep... try manually switching it if possible. Otherwise you have to pull the attenuators and manually clean them.

author: Disciple
author_rank: Newbie
timestamp: July 06, 2021, 10:14:52 am
content: Thank you all for your help. I was offline during few month due to a lot of work. I will try during my holiday to finish the repair.Thank a lot again !
HP 54522A oscilloscope bat and A/D problems - Page 1
Forum section: electronics / repair

author: HYCstudio
author_rank: Newbie
timestamp: July 13, 2025, 02:15:54 am
content: I got an hp 54522a oscilloscope recently，and it has the following problems.1.Cal. factor check run error(no more information,such as with cal ram error),then the cal. switch has been moved to umprotect,then the osc. seems run normally.(I set all the cal factor to defalt)2.The lithium bat,one capitor and one triode broken.3.Some times the Analog and A/D self test failed.I'try to fix it，But I have afew questions.Could any one help?1.I plan to change all the EC on the main borads.They are all NCC KME 105℃ 63v 100μf capitors，but the KME series seems halt production.Are those capitor in the digital circuit?I think so,Then I'll try to replace them with other series of EC.2.The lithium bat have 2v remaining,I'll change it.Did it needs to replace with out power interruption?3.The broken triode,on the boards possitionQ602could not be identified with the marks,the triode on the possitionQ601has the number 1855-0540.Is the Q602 the same model?If so,could I replace it with an normal2N5115triode without pairing?[ Specified attachment is not available ]I'm new in ee raparing,thanks for your help and comprehend.

author: Haenk
author_rank: Super Contributor
timestamp: July 14, 2025, 05:13:44 am
content: The battery leaked and I assume it even leaked into the PCB layers (which is bad).At least remove+clean or (better) replace the components around the battery; that quartz seems awfully corroded.

author: HYCstudio
author_rank: Newbie
timestamp: July 14, 2025, 11:05:51 am
content: Quote from: Haenk on July 14, 2025, 05:13:44 amIt's pretty strange that there are few ICs are corroded on the PCB,and they are in different possitions.Such as the triode is on the right corner,while a transceiver on the left corner.I think they're might corroded by the humid or something,not the leak from the batt.The other ICs and Capacitance around the bat are fine,I'll change a new quartz as well as a batt.Thanks for your suggest,but I still have no idea about should I change the batt with out try to not outage the power witch supply by the batt.

author: HYCstudio
author_rank: Newbie
timestamp: July 15, 2025, 04:59:43 am
content: oh then I think I can just remove it,It's no needs to keep the power up when replace

author: HYCstudio
author_rank: Newbie
timestamp: July 16, 2025, 02:22:31 pm
content: Update:ALL the ECs are replaced with rubycon YXJ 63v 100μf 105℃，the batt，quartz and the triode are removed,The new bat and quartz are in the transitI still have no idea about what the triode is,any one could help?thanks very much
HP 54540C Oscilloscope, SOFTWARE ERROR - PLEASE RECORD THESE NUMBERS - Page 1
Forum section: electronics / repair

author: Wayne916
author_rank: Newbie
timestamp: March 31, 2021, 02:17:00 pm
content: HP 54540C Oscilloscope, up to a week ago the scope was working and calibration completed with no errors, while testing an input signal i pressed the "Auto-Scale button" after a few clicks the scope locked up, and now will only show the below Error code, I have tried googling the error code unfortunately i could not find any reference."SOFTWARE ERROR - PLEASE RECORD THESE NUMBERS 9A8E 00102008 00FF"Following the service manual, I have checked the power supply module voltages both in circuit and with a 2 ohm load. All voltages found to be correct.I have replaced the bios 3.0v battery and installed the ROM and SYSTEM files from a 1.44 MByte floppy disk. Tried the two versions available, Unreleased software rev T2.26 and Released software rev 2.00.Both installed OK, but i still get the above Software error code.The mother board is 98% surface mount components, i have checked the caps for leakage and can see no signs of burnt tracks, removed and cleaned the ADC hybrid modules.HP54540C serial number US35480103internal psu = 0950-2369Any help would be appreciated.
HP 54542C problem - Page 1
Forum section: electronics / repair

author: stfjohn
author_rank: Regular Contributor
timestamp: August 02, 2019, 12:32:10 pm
content: Hello,My HP 54542C shows a channel crash probably due to excessive internal heat: in fact, removing the case, the problem no longer occurs! The fan works: what can the phenomenon be due to? Thanks to anyone who kindly wants to give me an answer.
HP 54600A Repair - Page 1
Forum section: electronics / repair

author: hiltz1
author_rank: Newbie
timestamp: November 07, 2024, 06:02:36 pm
content: Hello,I am attempting I fix a HP54600A I received broken.When I turned it on the screen displayed a solid thick line across the centre and it started to smell like the magic smoke...After dismantling, the sniff test narrowed in on two detonated tantalum capacitors on the motherboard.The two capacitors in the CRT driver that are common issues with this scope look visibly ok.Is there anything else I should check or that might also be damaged or do I have a good chance of repairing it by replacing those detonated caps?Thanks for any assistance!

author: coromonadalix
author_rank: Super Contributor
timestamp: November 07, 2024, 06:14:44 pm
content: for sure check voltages lines, if the tants have been changed, i dont know theses models, if sv manuals exists for themi dont know if somewhere you have a video signal you could check on a monitor ....your deflection seems reduced, and maybe we see faint characters ?? rolled up ?

author: hiltz1
author_rank: Newbie
timestamp: November 07, 2024, 06:23:24 pm
content: Once I have new caps I will check the voltages,I have found some manuals but no full circuit diagram.I think the faint characters visible are burn-in / image retention on the CRT as they are still there when fully powered off.

author: hiltz1
author_rank: Newbie
timestamp: November 07, 2024, 10:12:41 pm
content: I've replaced the caps as well as the two on the CRT driver responsible for vertical deflection.The display is now the correct size and showing a waveform although all of the text along with some of the other UI elements are missing.
HP 54600B - Page 1
Forum section: electronics / repair

author: Lokian666
author_rank: Newbie
timestamp: August 06, 2019, 06:16:38 pm
content: I recently picked up an HP 54600B. It seems to have a couple of problems. The auto-scale push button does not work. I need to press and hold the auto-scale button for a few seconds in order for auto-scale to work . Sometime, it takes a long time to output a waveform. Any fixes? Thanks
HP 54601A Noisy? - Page 1
Forum section: electronics / repair

author: mike4t5
author_rank: Newbie
timestamp: March 12, 2022, 06:17:42 pm
content: Hi there all,I'm new to this forum and electronics in general. I recently got a HP 54601A as my first scope for a decent price on ebay. First of all love the CRT on it, makes me want more CRT stuff now! I have been messing about with it and found the it seems really noisy. i don't know if its meant to be like this or if there's something wrong with it? I believe that there's an issue with it. i have an image of what i'm seeing. i don't really know where to start. hope someone can help me out please.

author: Vovk_Z
author_rank: Super Contributor
timestamp: March 13, 2022, 07:15:15 am
content: I don't see if "20 MHz" mode is turned on. Without it - it can be noisy.

author: mike4t5
author_rank: Newbie
timestamp: March 13, 2022, 09:25:53 am
content: Ah okay, I honestly have no idea if its on. Do you know how to see if its on? I don't see that as an option.

author: oPossum
author_rank: Super Contributor
timestamp: March 13, 2022, 12:19:22 pm
content: What does the cal output look like? Noise should be about +/- 1 LSB.Bandwidth limit (20 MHz) in in the channel menu.
HP 54601B Channels 2 & 4 "No Active Signal" - Page 1
Forum section: electronics / repair

author: bradyhylla
author_rank: Newbie
timestamp: July 01, 2019, 01:51:00 pm
content: Good morning folks, I have an HP 54601B 100MHz 4 Channel scope that wont display a trace on channels 2 and 4. Both channels will turn on but any function pertaining to the channels such as " Autoscale" yield a dialog "Scope cant find active Signal, Please check connections."I've tried different probes but get the same results. At first I thought it was an operator error but after reading the user/service manual sveral times and trying every setting i can find im still getting the same results. Google and youtube searches have all lead to dead ends. The troubleshooting section of the user/service manual suggested checking voltages at a few spots on the board and they were all fairly close to spec. none of the components on any of the boards looked damaged. I removed the front pannel and the BNC jacks are all firmly secured. No burnt plastic smells anywhere. i hear relays clicking when I hit auto scale for those channels but there no different from when i autoscale the working channels.Im still not 100% convinced its not and operator error. Could there be a setting that I overlooked? I'm still quite a newb with scopes and troubleshooting. Any suggestions are greatly appreciated. I've been scanning the forum for a while now and looking for answers all over the web but i keep coming to dead ends and beggining to pull hair.The picture Ive included is with all 4 Channels turned on. Channels 1 & 2 are both connected to the squarewave gen on the scope, 3 & 4 dont even have probes connected but you can still see that channel 3 will show still shows a trace but chanels 2 & 4 wont, despite being turned on.
HP 54616B PSU repair - Page 1
Forum section: electronics / repair

author: axemaster
author_rank: Contributor
timestamp: July 04, 2022, 08:34:21 pm
content: I've been using a HP 54616B oscilloscope for a few years, and recently the power supply seems to have died. I've opened up the scope and pulled out the power supply. Based on my examination of the PCB, the PSU architecture appears to be the following (in order):AC input, fuse, mechanical power switchpowerline filterisolation transformer (1:1)bridge rectifier to mains voltage DCflyback transformer primary + big N-chan MOSFET for switchingflyback transformer secondary, multi-tapbunch of low-voltage rectifiers and regulatorsRibbon cables to carry the power throughout the scopeTesting the PSU, I found that everything seems to work fine up to #4 - the mains DC voltage is present. However, there is no switching of the MOSFET. As a result, no power is transmitted across the flyback transformer, and there is no power at all on the secondary side.I probed the MOSFET gate and there is no logic signal. So I believe the circuit responsible for generating the switching signal has failed.I am currently probing step by step through that control circuit.Does anyone know the correct switching frequency for the flyback transformer? In the worst case, I could jury-rig my own controller.Also, it would be very helpful to know the correct DC output voltages from the supply. Is this documented anywhere?Thanks so much for your help!

author: axemaster
author_rank: Contributor
timestamp: July 04, 2022, 08:44:03 pm
content: Here's some supporting info:Switching MOSFET = IRFPC50https://www.vishay.com/docs/91243/91243.pdfSwitching controller IC = UC3842https://www.ti.com/lit/gpn/uc3842----> I have measured the output pin of this IC and there is no logic signalSwitching controller optocouplers = TCDT1103https://www.mouser.com/datasheet/2/427/TCDT1100-1767073.pdfSome of the transistors near the controller = MPS6651https://www.mouser.com/datasheet/2/308/1/MPS6601_D-2316415.pdf"Precision shunt regulators" near the controller = AS431https://www.diodes.com/assets/Datasheets/AS431.pdfNOTE - I also have a HP 54600B. I opened it up with the idea of cannibalizing the power supply. But the PSU for that scope is clearly a different model (though similar).NOTE - Found DC test point voltages on page 132 of service manual...

author: xavier60
author_rank: Super Contributor
timestamp: July 05, 2022, 02:23:53 am
content: Check for open circuited high value resistors.
HP-54720D Oszilloscope Powerconnector in Front of Modul 54721A? requierd? - Page 1
Forum section: electronics / repair

author: weakbit
author_rank: Newbie
timestamp: February 23, 2020, 06:40:05 am
content: Hello Mr.James,my first post, I'm Radio & TV mechanics but I do not work in this business anymore - I've got very ill in 2017 but I can't site on my back and wait when the death is comming so I do some littel things - like to renovate my Lab and in this Lab I've a lot of different old measurment equipment like Spectrum Analyzers, Oscilloscopes, CRT-Monitors, Power Supplys etc.I'm searching a information about the connector in front of the inserted modul 54721A?What is the name of this Power connector for a aktiv probe?Where I can get this?I bought this Oscilloscope at eBay in 2008 or so and hold it on stock till today now I'll start it but there are no probes available so I build with a Ukrain "probe for the poor" two new aktiv probes.But there is a power supply needed and on the frontend of the 54721A is a poweroutput but I can not find the correct pinout for this connector and I never see a connector like this in the last 35years since I'm in business?Please can you help me? On the pictures you can see the insters 54721A and exact on this is the N-Connector for the Signal and the little power connector is required?On question more - where is the dumpster where you find the 35GHz (80Gs/s) Oscilloscope? I'll also find one of this too!Best Regardsweakbit
HP 54815A Infinium Scope- PC boot problem - Page 1
Forum section: electronics / repair

author: Tracker
author_rank: Regular Contributor
timestamp: November 13, 2021, 05:12:48 pm
content: Hi Folks,I have a faulty HP 54815A boot problem....The AMI BIOS boot sequence stops at:CMOS Settings WrongCMOS Display Type WrongKeyboard errorPress F1 to Run setupPress F2 to load default values and continueIt also was reporting a battery problem, but I resolve 3.3v external CR2032 on the Dallas Realtime clock.I also tried to reset the CMOS using the motherboard jumpers.So now I reckon it needs to load default values with F2But here is where I become unstuck!I don't have an IBM AT type keyboard!!! yikes!Wonder if I can I wire a USB keyboard to the Clock and data lines of the AT keyboard socket?Also, I checked the AT keyboard socket has +5v but I also noticed one of the data lines was also at +5v, this seems odd.I suspect this might why I'm seeing the Keyboard error on boot screen, wonder if the Motherboard has an I/O fault?any advice welcome...Thanks in advance

author: coromonadalix
author_rank: Super Contributor
timestamp: November 13, 2021, 05:22:30 pm
content: Some ps2 keyboards can or could accept the AT to PS2 keyboard adapter, an usb keyboard will not work unless you put some interface between themI have one in my old stuffhttps://www.amazon.ca/kenable-AT-Keyboard-PS-Adapter/dp/B003OSTBZAhttps://www.amazon.ca/Keyboard-Adapter-6-Pin-Mini-Din-Female/dp/B00005114F/ref=dp_prsubs_2?pd_rd_i=B00005114F&psc=1

author: Tracker
author_rank: Regular Contributor
timestamp: November 13, 2021, 10:48:27 pm
content: Thanks for that, I might ask my local PC repair shop if he has any old keyboards.