hybridfree/eevblog-posts huggingface dataset:
HP 3458A VFDs - Page 1
Forum section: electronics / repair

author: perdrix
author_rank: Frequent Contributor
timestamp: October 12, 2019, 02:58:38 pm
content: Looks like someone in China has found a case of the VFDs used in the 3458A! eBay item number 113920233966Not cheap but ...David

author: Bill158
author_rank: Regular Contributor
timestamp: October 13, 2019, 05:06:30 pm
content: There are several questions to be concerned about on these VFD displays.1. Are these the "old" pin spacing?2. Who manufactured these VFD displays?3. Are they original H/A/K parts or knock offs?I purchased a 3458A VFD display 2090-0217 a few years ago when they were being listed as available for sale on the HP/Agilent/Keysight website, without having to buy the entire Display PCB assembly. It was around US$80 as I remember. After I had removed the old VFD from my display PCB, which was a job in itself (60 pins), I discovered that the pin spacing from top to bottom of the new display was 1.6 inches while the PCB and the old display was 1.4 inches. It took hours and hours to carefully bend and then insert 60 pins into the old board. After I was done the display worked correctly as expected. But apparently H/A/K had redesigned the Display PCB to accommodate the new pin spacing of 1.6 inches. BUT the part number was the same. So my question on these displays is pin spacing.A friend found a source of 3458A VFDs a year ago or so. The best as I can determine these come from "TAOBAO" athttps://item.taobao.com/item.htm?spm=a230r.1.14.46.14590d6eLuFDRV&id=538154307229&ns=1&abbucket=6#detail. The price is ¥750 which seems to convert to around US$105. So with handling and shipping the final price was around US$150 each. He ordered 1 initially to try out and then ordered 3 more total for himself, another friend and me. I still have mine because I don't have a need to install right now, just hedging against the future. The originals from H/A/K are made by NORITAKE. These from TAOBAO are NOT (obviously a Chinese knock off), but work just fine and are brighter than the originals. Also there are physical size problems, as my other friend who did not order these, found out. There was a shield that was touching some of the pins which he didn't see when he did the installation, but with a little bending fixed the issue. Also the VFD from TAOBAO has the 1.6 inch spacing which means I face another 1 day task of changing once I have to do this job. Also from what I can see in the various listings on ebay most of these seem to be the knock offs. The "give away" is that the knock offs have a small "circular" something in the lower right corner of the display which appears to be a "getter" as we used to call it in the old vacuum tube days. The only listing that I see that looks like NORATAKE is 293250709061 but it is very hard to tell from the photo.Bill

author: SilverSolder
author_rank: Super Contributor
timestamp: October 15, 2019, 07:35:35 pm
content: Quote from: Bill158 on October 13, 2019, 05:06:30 pmVersion control... gotta love it!Maybe the board had a different rev letter even if the part number stayed the same?
HP 3467A - Logging Multimeter - Page 1
Forum section: electronics / repair

author: cluster2600
author_rank: Newbie
timestamp: June 04, 2020, 08:34:31 pm
content: Hello all,I am trying to find a repair manual for the HP 3467A - Logging Multimeter the PDF on keysight is unreadable.Thank you in advance.cluster2600

author: Wytnucls
author_rank: Super Contributor
timestamp: June 04, 2020, 10:20:19 pm
content: https://www.eevblog.com/forum/repair/repair-hp-3467a-showing-no-display/
hp 3468 A ROM dump - Page 1
Forum section: electronics / repair

author: olometaboy
author_rank: Newbie
timestamp: July 18, 2019, 05:32:33 am
content: HiA friend of mine have one hp 3468 A. It reset in loop and after some verification we have find the problem "corupted ROM".I have find online this rescure of similar DMM whit the creation of new rom from old pc bios chiphttps://xdevs.com/fix/hp3456a/but to do the same on 3468 I need the firmware dumpSome one that have this?Have good day

author: MarkL
author_rank: Unknown
timestamp: July 18, 2019, 09:23:29 pm
content: Have a read through this thread:https://www.eevblog.com/forum/testgear/hp-3468a-owners-unite-a-storm-is-coming!/msg687107/#msg687107There are a couple of ROM images for the 3468A posted within, plus other info about replacing U502.EDIT: Fixed mangled url reference.

author: olometaboy
author_rank: Newbie
timestamp: July 18, 2019, 10:33:28 pm
content: Very good the eev comunity is the best I have find the rom and the solution on page 3https://www.eevblog.com/forum/testgear/ ... oming!/75/Thank you very much
HP 3478A DMM LCD lighting - Page 1
Forum section: electronics / repair

author: gdnichols31
author_rank: Regular Contributor
timestamp: September 28, 2020, 12:09:40 am
content: Has any one tried to add a back light (or edge light) to one of these? I love the meter but is really hard to see.I searched the forum and didn't see anything.ThanksGary

author: pqass
author_rank: Super Contributor
timestamp: September 28, 2020, 01:09:55 am
content: The 3457A and a few other models of the era share the same LCD.See (side LEDs and EL backlight hacks):https://www.eevblog.com/forum/projects/hp-3457a-lcd-backlight-mod-(also-for-3478a)/Also:See "Backlight modification for display" near the bottom (meh result):https://xdevs.com/article/hp3457a/Or for the daring:https://www.eevblog.com/forum/projects/led-display-for-hp-3457a-multimeter-i-did-it-)/For my 3478A, I opted for an IKEA clamping gooseneck LED spotlight instead.

author: Miti
author_rank: Super Contributor
timestamp: September 28, 2020, 02:48:26 pm
content: Quote from: gdnichols31 on September 28, 2020, 12:09:40 amI did. Check out this project.https://www.eevblog.com/forum/testgear/hp3478a-backlight-my-version/msg1505830/#msg1505830

author: gdnichols31
author_rank: Regular Contributor
timestamp: September 29, 2020, 12:49:41 am
content: Wonderful information guys, thank youNot sure why it didn't show up on my search.Gary

author: wiesl
author_rank: Contributor
timestamp: March 16, 2021, 02:28:26 pm
content: Great mod!
multimeter hp 3478a not  stable \ chatter \ jumping zero values - Page 1
Forum section: electronics / repair

author: truser
author_rank: Newbie
timestamp: September 30, 2019, 01:17:05 pm
content: All input connected together.There is no zero and the values are jumping.Power on a 5 hours, the result is the same.What problems ?Where to dig?Thank'shttps://youtu.be/SEVjhzueS90

author: Ringmodulator
author_rank: Regular Contributor
timestamp: September 30, 2019, 02:10:55 pm
content: Hi,check the contacts between the 4mm front panel probe sockets and the cables inside the unit.I had quite high Ohm display with the input shorted out for 2 wire measurement.Cleaning and reseating the spade contacts solved this.RegardsChris

author: truser
author_rank: Newbie
timestamp: November 12, 2019, 05:43:23 am
content: Thanks, check it out.But I do not think that this is due to my problem.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 12, 2019, 08:08:46 am
content: The ohms reading problem could very well be a contact problem, especially if measuring 2 wire ohms. If 4 wire Ohms, it depends on how the cables are connected.For the mV readings, there could be some thermal EMF from holding the DMM in the hand. The 3478 is a bench top meter, not a hand held. I would not expect that much trouble, but for best stability it should sit on a bench / board and not moved around.The first points to check would be the supply and the line frequency setting (50/60 Hz). Also check the integration time - the preferred setting for manual reading is something like 10 PLC or more. Another point would than be looking at the DC zero reading in the 30 mV / 300 mV and 3 V range. This should tell if the problem is more with the ADC or the input amplifier.
HP 3478A, random display - Page 1
Forum section: electronics / repair

author: munorc
author_rank: Regular Contributor
timestamp: March 30, 2025, 02:24:08 pm
content: I have three HP3478A DMM's. All acquired surplus at the same time. Two are a bit newer and only differ by 2 in serial number.They were all functional when acquired back 10 years or so back.One has been working fine. One has lost its calibration (3V battery died). I was able to provide various inputs and did a "transfer" calibration of that one comparing it to the functional one. At some point it will need a better calibration, but it is functional.The third one no longer powers up properly, it just randomly shows segments on the display. It never fully come on line since it does not show up on the IEEE-488 bus, so I do not think it is just a bad display.I checked the power supply side and the 5V and +/-15V measure fine. Those caps look fine, but most likely need replacement. I have replacements for the "RIFA" caps for the line side, but have not replaced those yet.Looking at the digital side, it seems the U760 voltage regulator may be suspect. It measures >5V on the unregulated side and only 4V on the regulated side. Compared to the working units, they measure 5v as expected.It seems there were many revisions on this unit. The one that is fully functional is older by serial number, and the main board definitely has some differences. I find a service manual on line at Keysight (dated 1987). I also find many other ones online, but most seem to be the same manual. The schematics seem to fit the two newer units.However, U760 is spec'd as HP part number 1826-0551 and listed as a LM3040AT-5. This part in all three units is a 1826-0536, which cross references to LM3040AK-5. Looking on line it looks like these are made of gold, with prices of $65-$90+ each. It is a TO-3 package. Other variants are much more reasonable.Is there any functional difference between these? I did manage to find some LM3040AK-5 NOS surplus for $5, so not a huge investment to see if it is the issue.EDITLooking closer at the service manual, I see the Backdating chapter addresses changes.Oldest unit is < 2136A03480The two others are <2301Al8860It does not have any mention of the change in part number for VR U760. Troubleshooting indicates this could be the cause of low voltage, along with the nearby cap and Zener diode. The latter appear to be fine.

author: hiwi
author_rank: Newbie
timestamp: March 31, 2025, 02:31:09 pm
content: Hi,there may be a short on the secondary side of U760 so I would disconnect the output and measure the voltage before ordering a new regulator.Look into the specs of the TO3 version,older ones have only 1.5A or such, there are modern TO220 versions with more than 2A, so you can replace the TO3 with To220 if you can#t find it.Check the pinout, isolation and heat transmission.replacing the Rifas and the big caps in the PSU is a good advice.Ralf
HP 3480A / 3484A repair/restoration - Page 1
Forum section: electronics / repair

author: Nevada
author_rank: Contributor
timestamp: May 16, 2021, 05:05:57 pm
content: Hello,I recently acquired a nice HP 3480A multimeter from the (original) Nixie-era with a 3484A module. Unfortunately the seller disassemled the module earlier, and he removed the option cards. I re-installed them (although the screws are missing), but there are five wires which I don't know where should I connect. I didn't find any information about that in the service manual.Could somebody help me?

author: factory
author_rank: Super Contributor
timestamp: May 18, 2021, 07:44:19 pm
content: If you haven't already downloaded it a manual covering the later revision boards in your 3484A can be found on the Keysight website under 3480D 3484A and older first edition is on hparchive.The only one that is obvious is the green wire from the top board in the picture (A6 ohms/DC convertor) should go to the Ω connection on the lower board (A1 attenuator).Is the orange wire is from the AC board (A7)I guess you need to identify the components on the middle board (A2 DC amplifier) that the wires are connected to and trace through the diagrams to see if you can work out where they should go. The three wires are shown between the A1 & A2 circuits as the color codes; red (2), black (0, low current ground) and green (5, filter amp output).David

author: Nevada
author_rank: Contributor
timestamp: November 05, 2021, 02:21:00 pm
content: David,Thanks for your suggestions! Finally I could made them working, but unfortunately it turned out, that somebody killed its most interesting part: the 10MHz RMS converter...Although the basic function (DC voltage) works ok.

author: factory
author_rank: Super Contributor
timestamp: November 06, 2021, 05:59:26 pm
content: Never noticed before that the RMS converter (11153A) option was covered by a separate manual, luckilyhparchivehave it.That part is the thermocouple, guess finding a replacement would be impossible, as most 3484A plug-ins didn't have the AC or ohms options.This seller has destroyed a 3484A with all options.https://www.ebay.com/itm/293079335436I'm now looking for a 3484A for my 3480B, it has a 3481A buffer plug-in, this one seems to very uncommon, can't even find a manual for it, either free or paid for.David

author: doktor pyta
author_rank: Frequent Contributor
timestamp: November 07, 2021, 09:02:53 am
content: sounds familiarhttps://www.eevblog.com/forum/testgear/hp3403c-marvels-(photos)/msg3349034/#msg3349034

author: factory
author_rank: Super Contributor
timestamp: November 07, 2021, 01:19:52 pm
content: That does look similar, wonder what the differences are? as they have different part numbers.The digital panel voltmeter for the 3404x was used for other HP test gear too, or sold on it's own as the 3431x.David
HP 3497A Self Test error code - Page 1
Forum section: electronics / repair

author: VitaliyR
author_rank: Newbie
timestamp: September 27, 2025, 07:29:01 pm
content: I have an HP 3497A that shows a number "3" when I run self test thru front panel.I don't have original manuals, but all the manuals I was able to find only don't show this as being a legitimate error code.Please see the picture attached.Anyone know what this error could mean?

author: trobbins
author_rank: Frequent Contributor
timestamp: September 29, 2025, 12:50:13 am
content: The 03497-99000 HP3497A programming pdf indicates a '3' may relate to 'Timer fails' condition.I initially had a ST=2 condition, with a faulty zener in the In-guard supply rail +30L, then it passed.

author: srb1954
author_rank: Super Contributor
timestamp: September 29, 2025, 02:50:07 am
content: Check if there is an internal battery and the state of charge of that battery.Some versions of the 3497A had a rather weird RTC circuit based on an 8048 microcontroller. This was run off the battery supply and, if the battery is flat, the main controller may not be able to communicate with the RTC circuit.Since the RTC circuit used quite a bit of current it needed significant sized (from memory 6V 4.5AH) lead-acid battery to provide back-up power. If the 3497A is not continuously powered from the mains that battery will run flat quite quickly.
HP 3561A DSA Repair Series - Page 1
Forum section: electronics / repair

author: TheDefpom
author_rank: Frequent Contributor
timestamp: March 02, 2022, 08:45:27 am
content: I picked up a faulty HP3561A to repair and make videos about... here is the repair series, the repair is currently still ongoing.Part 1:Part 2:Part 3:Part 4:Part 5:Part 6:Part 7:TBA

author: TheDefpom
author_rank: Frequent Contributor
timestamp: March 12, 2022, 10:24:26 am
content: Part 7:
HP-35660A Dynamic Signal Analyzer full service manual ? - Page 1
Forum section: electronics / repair

author: RichardM
author_rank: Frequent Contributor
timestamp: January 19, 2022, 01:32:43 am
content: Tried asking on the Keysight group (groups.io) with no luck.I have managed to find links to several pdfs of the 35660a service manual but it appears none of them are complete? Including the one from Keysight? I.e. Section III Adjustments ? Section VII etc, Am I misreading something ? Does anyone have a link to the complete servive manual ?Much appreciatedRegardsRichard
HP 3577A - Page 1
Forum section: electronics / repair

author: bat
author_rank: Regular Contributor
timestamp: May 23, 2025, 12:15:05 pm
content: Hi y'allMy HP 3577A has a very unstable CRT display. It's more than the common CRT jitter, the whole display is unstable. If you look carefully on the grid, you can see what i'm talking about. My phone wasn't able to clearly film the CRT.I think I will have to replace the aging electrolytic caps.The CRT is still in good condition, focus is good and brightness is okay.Here's the videohttps://youtube.com/shorts/UOOIOrzg8-Q
HP 3580A No Trace  - Page 1
Forum section: electronics / repair

author: arcsound
author_rank: Newbie
timestamp: October 25, 2023, 03:22:51 am
content: I just purchased an HP 3580A that had a working display prior to shipment to me.However when I tried powering it up after receipt, I get no trace at all.There are bulbs illuminated on the front panel, so I know it is getting voltage.Although well packaged by the shipper, I suspect it had a rough transmit, judging by the nice sized hole in the cardboard box.So:1. What is the likelihood that the CRT was damaged?2. What is the possibility of finding a replacement CRT, if it is the CRT?3. What is the best way to rule out a bad CRT?Thanks for any and all help!

author: p.larner
author_rank: Frequent Contributor
timestamp: October 25, 2023, 07:19:50 am
content: without seeing the unit, its hard to tell,have you checked foe pda eht on the anode cap?.

author: Greybeard
author_rank: Frequent Contributor
timestamp: October 25, 2023, 07:43:40 am
content: Check this:-intensity pot-internal supply voltages and ripple-DC voltages at the CRT-sawtoothdeflection voltages at the CRT-blanking circuit-trigger circuitedit: sorry, my bad, I have overlooked you have spectrum analyzer, not a simple scope...

author: arcsound
author_rank: Newbie
timestamp: October 25, 2023, 03:59:34 pm
content: Quote from: p.larner on October 25, 2023, 07:19:50 am"...foe pda eht.."?Thanks, but I don't understand. Could you elaborate, please?

author: arcsound
author_rank: Newbie
timestamp: October 25, 2023, 04:01:31 pm
content: Quote from: Greybeard on October 25, 2023, 07:43:40 amI have to figure out how to safely measure -3KV with my Fluke 8060A now...

author: p.larner
author_rank: Frequent Contributor
timestamp: October 25, 2023, 06:26:33 pm
content: try thishttps://www.instructables.com/High-Voltage-Probes/

author: factory
author_rank: Super Contributor
timestamp: October 26, 2023, 06:14:39 pm
content: Given the high asking prices for these I would have sent it back, item not as described. Where exactly was the hole in the box, in relation to the 3580A? Guessing at the back (where the CRT socket sticks out), given the controls aren't broken.Better to go and collect/pick up in person anything with a CRT (especially if it's electrostatic deflection), that way you can see it working (if it was of course) and take better care of transporting it home.David

author: Jwillis
author_rank: Super Contributor
timestamp: October 28, 2023, 03:19:58 am
content: First thing I would check is all internal connections and boards are well seated.
HP 3582a problems with buttons  - Page 1
Forum section: electronics / repair

author: akabek
author_rank: Contributor
timestamp: January 11, 2024, 01:28:04 pm
content: I have a HP 3582a and some of the buttons should have two positions but when pushed in they do not lock into the lower position. Can these buttons we taken out, dismantled and repaired or do I need to find replacements?
HP 3785A Jitter Analyser Battery Replacement - Page 1
Forum section: electronics / repair

author: Simon_RL
author_rank: Regular Contributor
timestamp: November 26, 2020, 11:12:21 am
content: I am trying to get a HP 3785A up and running. There's not much wrong with it that can't be easily fixed. My biggest problem is finding a replacement battery. It is an AA (I think) 3.6v 100mah rechargeable (see photos below). It has a code on the side 1420-0282, which I have tried searching but no luck. There is also a link below to a tear down by Dave of the same device, @ 23:47 you can see the battery and board it is on.I have also spent hours searching for a user and service manual, both the web and here on the forums. I have also followed the many links provided here on the forum to user/service manual download site and not had any luck either. My biggest issue is I don’t know the battery chemistry, while I am guessing it is alkaline given the age of the device, but I am no expert when it comes to batteries and don’t want to replace with the wrong chemistry.All help very is much appreciated on either replacement battery or service manual.

author: wn1fju
author_rank: Frequent Contributor
timestamp: November 26, 2020, 12:29:05 pm
content: My guess is that it is a NiCd battery. All my HP pieces of that vintage that had rechargeable batteries inside were NiCd. Presumably the battery is used to provide voltage to the RAM to hold settings, etc.I don't particularly like NiCds in these old pieces for two reasons: 1) they eventually leak, 2) I never use the piece enough to keep them recharged.What I usually do is substitute regular alkaline batteries. If there is suitable space, I put two AA (or AAA) batteries in one of those cheap plastic covered holders (so when they also leak, the stuff is contained) and put a Schottky diode in series (to prevent charging). Never had a problem doing that.

author: Simon_RL
author_rank: Regular Contributor
timestamp: November 26, 2020, 09:09:24 pm
content: Quote from: wn1fju on November 26, 2020, 12:29:05 pmThanks Heaps wn1fju, that is exactly the info I was looking for
HP 3850B Sweep Oscillator power supply fluctuation - Page 1
Forum section: electronics / repair

author: tonycox01
author_rank: Contributor
timestamp: May 15, 2021, 11:40:27 am
content: HiI am bringing an HP 8350B sweep oscillator (with a 83952C RF plugin) back to life. It would not start up (kept blowing fuses) - which was down to a semi-seized cooling fan and an intermittent plugin/chassis connection.Having got it running stably I'm beginning to check it out. The first thing I looked at was a main power rails. I've let the 8350 (and HP 3456 I'm measuring it with) warm up for an hour and checked the -40V, +20V and -10V volt rails.All are close - but definitely out of spec because they are all "wandering" above and below the spec value:+20V: 20.007V - 19.990V-40v: -39.993V - -40.010V-10V: -9.9979V - 9.9984VThey all go through their fluctuation range at about the same rate (~1-2 seconds).I was hoping the kind souls on this forum may be able to give me some advice on where best to start. My thought was that there is some ripple in the PSU that may be causing this - but any pointers before I dive it would be very welcome.thanksTony(apologies - I accidentally posted this to the "Test Equipment" forum first)

author: wn1fju
author_rank: Frequent Contributor
timestamp: May 15, 2021, 12:09:04 pm
content: Am I missing something here? According to Table 8-23 of the service manual for the 8350B, your voltages are within the limitsThe fact that they are fluctuating slightly would not bother me at all. But just to be certain, check them with an oscilloscope. Just measuring power supply voltages with a DC voltmeter can overlook a lot of AC ripple, because the voltmeter will simply give you an average value. Ripple would point to problems with a capacitor or diode bridge. But the fact that you see movement in all (separate) power supplies leads me to think everything is actually fine.The power supplies are loaded by whatever the rest of the circuitry is doing. See if the 1-2 second fluctuation rate changes as a function of the various sweep rates. Could all be perfectly normal behavior.

author: tonycox01
author_rank: Contributor
timestamp: May 15, 2021, 12:34:01 pm
content: Hi wn1fju,Thanks for your help. I just found Table 8-23 and as you say they look fine. I was working from my service manual (Section 5-1: Adjustments ) where the specs are as follows:+20.000V +/- 0.001V-40.000V +/- 0.002V-10.000V +/- 0.001VAs you suggest I'll get the scope on the supplies and check them - and I hope I was worrying about nothing :-)thanks aganTony
HP 400FL AC Millivoltmeter - Page 1
Forum section: electronics / repair

author: oldsoul
author_rank: Newbie
timestamp: March 23, 2024, 11:44:28 am
content: I have this unit in complete stock condition. The problem is randomly the needle will bounce all over the place or just stay at zero. Then if I tap on the case the needle will sometimes return to its measured value. Sometimes not.

author: donlisms
author_rank: Frequent Contributor
timestamp: March 24, 2024, 05:55:09 am
content: Have you done anything to try to find the problem? Have you taken the covers off and poke at things with an insulated stick to try to see what part is most sensitive?

author: oldsoul
author_rank: Newbie
timestamp: March 25, 2024, 12:30:00 am
content: I did take the panes off. My mistake it does look like someone did replace a few of the electrolytic caps. The only thing I notice is if I move the wire going to the meter the meter jumps a little. When under test and the needle operating properly it will out of nowhere just go wild and often just bury down to 0

author: jonpaul
author_rank: Super Contributor
timestamp: March 25, 2024, 01:40:56 am
content: hello all the old classic analog meters suffer from paint and debris chips off the faces.These enter the D'Arsonval movement and cause sticking and blocking.Turn meter on its face, gently tap sides and see if it improves or changes.Often the debris clogging will fall down to the face and can be see and removed.I have many similar meters and never had to replace any lytics, the HP 197-0s..1990s were top quality.Bon chance \Jon

author: Kosmic
author_rank: Super Contributor
timestamp: March 25, 2024, 01:19:04 pm
content: I would still check electrolytic capacitors. I had to change one in an erratic 400e.
HP 410C Meter pegs upscale Check A1R10? - Page 1
Forum section: electronics / repair

author: wd5jfr
author_rank: Regular Contributor
timestamp: November 01, 2024, 08:19:07 pm
content: It was working fine on resistance measurement, but then, after about 15 minutes, the meter pegs upscale, and the manual shows the possible cause as A1R10 250 ohms. I think it's an intermittent cold solder joint or a failing 250 ohm resistor. At 84, my eyes aren't that good, so I need some help. If someone has an open unit, a picture or a description of its location would be nice.ThanksHank

author: wd5jfr
author_rank: Regular Contributor
timestamp: November 01, 2024, 11:09:25 pm
content: Scott o n antique radio sent a pic here:https://antiqueradios.com/forums/viewtopic.php?t=442625
HP 410C - Page 1
Forum section: electronics / repair

author: wd5jfr
author_rank: Regular Contributor
timestamp: June 05, 2023, 09:48:17 pm
content: Got a solid state one with no red paint on the low AC meter scale. Not sure if it's original or been upgraded to SS because it has the A3 0041066502 Rev E 88809F PC board. My 410C serial No. 098A214826 and my manual is for 0982A22439. I'm having difficulty calibrating 0.5 VAC and can't find anything in my manual which refers to adjusting A8R8 ZERO ADJ on rear of cabinet. Any suggestions or info appreciated.Hank

author: m k
author_rank: Super Contributor
timestamp: June 12, 2023, 02:43:19 pm
content: I'm reading HP Archive manual 01556-5 from Sep-68.Its 5-11 a. has a ZERO ADJ for DCV accuracy check.Seems that it is a dynamic thing and for the moment.For 0.5 VAC,are you doing the AC voltmeter calibration?(page 39/68 of above manual)
HP 412A repair, Improper readings - Page 1
Forum section: electronics / repair

author: Arty30
author_rank: Regular Contributor
timestamp: August 09, 2025, 10:26:53 pm
content: Hello all, I'm working on an HP 412A VTVM that I revived a bit ago and I'm revisiting. when I got it the photo-chopper motor was sticky and a couple of bulbs were bad. I got the motor spinning and did an LED conversion, and a deep clean. The unit "works" now, the gauge moves and such, however volts DC reading is suspiciously close to measuring 3x the actual voltage. almost as if the range is shifted over one, but I checked. Ohms is also not correct and reads low. I didn't replace any components so now I'm looking for any tips and advice on where to look first. Are there any parts that should be refreshed? is there a procedure to calibrate the unit at home? are there any good ways to verify my LED conversion didn't throw off the whole system? Any answers would be greatly appreciated. the manual's procedures use gear that I'm sure not many people have so I didn't get far. Thanks.Arthur.

author: doktor pyta
author_rank: Frequent Contributor
timestamp: August 10, 2025, 10:38:04 am
content: Hi,how are the LEDs powered? With DC or AC voltage?

author: Arty30
author_rank: Regular Contributor
timestamp: August 10, 2025, 01:08:11 pm
content: With DC, I'm taking the 6.3V from the bulb socket and running it though a bridge rectifier and filter.
HP 4195A battery - Page 1
Forum section: electronics / repair

author: rumreich
author_rank: Newbie
timestamp: November 26, 2020, 06:20:26 pm
content: I acquired an HP 4195A that had been in storage for a few years and it appears to work properly in every way.I thought I'd preemptively replace the backup battery A6BT1 and ordered a COMP-34SPC 2.4V NiCad.When I pulled the A6 card out, I discovered that the battery had been replaced with a TADIRAN 3.6V lithium battery and R28 was clipped on one side. This is a non-rechargeable battery and R28 is a series resistor in the battery charging circuit.Is anyone familiar with this approach? I can't decide whether to leave it as-is or install the NiCad and resolder R28.Thanks in advance for any comments.
HP 4195A VNA Issues - Page 1
Forum section: electronics / repair

author: outlawpsd
author_rank: Contributor
timestamp: August 29, 2022, 04:01:52 pm
content: Having some issues on the VNA side of my 4195A. Spectrum analyzer side appears fine. This 4195A lost is config so I'm not sure if its related to that or there is another problem. I have not read anywhere that this has multiple bands that it has to shift between so looking for a good place to start. I have read that the DAC (U18 on the A51 board) in the test sets seem to be an issue for more than one person, could this be related to the DAC failing?

author: RomDump
author_rank: Regular Contributor
timestamp: August 30, 2022, 11:06:53 pm
content: Quote from: outlawpsd on August 29, 2022, 04:01:52 pmI think you are talking about the MDAC. Thisvideoshows the symptoms and how to repair it, (sorry it is in french so turn on CC with auto translate). As I mention before in your other post, post your message on the hp groups.io group or search the group for 4195A. Someone else already had the same issues you are describing, (I think he also posted a video how he calibrated the 4195A after he repaired it).

author: outlawpsd
author_rank: Contributor
timestamp: September 01, 2022, 10:28:02 am
content: Thank you for posting that video, believe it or not it was a big help. I've looked through the HP.IO groups and downloaded the Python script that has been posted for the calibration procedure but unfortunately, I have never used Python before. I installed Python but not really sure what to do next - I've got to get up to speed on how to make all that work first. Plus it looks like there are multiple .py files and there isnt a procedure written on how to use them. I dont know what needs to be done first, second, etc. Got a lot to learn.

author: outlawpsd
author_rank: Contributor
timestamp: September 06, 2022, 12:15:57 am
content: Just wanted to follow up on the repair of the initial issue that I posed about. I replaced both A50-U26 and A51-U18 with a Maxim MX7523JN and everything is working now. I didnt have the tools to figure out if it was on the transmit or receive side so I took a bit of a shotgun approach to it. Now on to figuring out the cal.
HP 4263B lcr help to repair  - Page 1
Forum section: electronics / repair

author: Zolonon
author_rank: Newbie
timestamp: November 21, 2024, 08:06:40 pm
content: Please helpI want to find the connection point between the mainboard and the dc-dc red wire in 4 pin connector. Which device on the mainboard (in the red circle in the first picture) does it connect to and what is the voltage?Where does it connect to? I can't see the circuit in the middle layer. (Left side in last picture ) where connect to componentThank you for help

author: TERRA Operative
author_rank: Super Contributor
timestamp: November 21, 2024, 10:58:19 pm
content: Here's the pinout from my 4263B:Left to right (viewed from front of instrument) - Red, Black, Yellow, Black.Voltages:Red - 2.68V (DC Bias supply?)Black - GNDYellow - 16.0VDCBlack - GND(GND pins are connected together)Also, check out my unlock program if you want to activate options 001 and 002 if not already activated on your instrument.https://github.com/JaredCabot/HP-Agilent-4263B-Option-Unlocker
HP 4277A/4276A power supply issues - Page 1
Forum section: electronics / repair

author: ZGoode
author_rank: Frequent Contributor
timestamp: June 18, 2024, 01:19:05 am
content: I got my hands on a cheap HP 4277A LCZ meter a while ago that seems to have power supply problems. I have been trying to work my way through the service manuals for the 4277A and 4276A, but can't identify the bad components. I have checked all fuses, and replaced all RIFA caps. I have also replaced the Q10, Q11, Q12 transistors with known good parts. So far all other parts I have checked appears to be within spec. For the first check in the troubleshooting guide it says to check for 12V at a test point on turn on that goes quickly down to below 3V. When turning on it goes to around 8.5V and then dips below 3V very quickly. Anyone have any other ideas as to what could be going on here?

author: ZGoode
author_rank: Frequent Contributor
timestamp: June 18, 2024, 01:20:08 am
content: Reply to add picture of board. There is that burnt section near the D2298 transistor, but it appears to be fine now, and that resistor connected there appears undamaged.

author: jonpaul
author_rank: Super Contributor
timestamp: June 18, 2024, 04:57:34 am
content: Our 4277A never had any issues.random parts replacement is not reccomended. This switching power supply is complex and hard for troubleshooting if you have little SMPS expericence or equipment.(variac, isolation trsf, probes, etc. )1/ Find full PDF and printed service manual for your model and serial number range.Artech still prints good reproductions. Beware that The PDFs vary widely in quality2/ Read and understand theory and curcuit description3/ Follow troubleshootong proceedure for affected section , in the flow chart4/ find the issue. Fix. Test, adjust calibration if needed.DONE!Good luck,Jon

author: ZGoode
author_rank: Frequent Contributor
timestamp: June 18, 2024, 08:31:22 am
content: I've been mainly working off the 4276A manual, since it appears this board is most likely the same between the 4276A and 4277A (and since that version of the manual appears to have better scans that I could find)This board is behaving really weird, and makes me feel as if U1 might be the problem. Since when I remove the 250mA fuse (F1), it appears to test like how it should in the first sections of the flow chart (12V on startup, going down quickly to less than 3V). As soon as I put the F1 fuse back in and then turn it back on, it goes back to behaving weird with the test point measuring around 8V on startup. I'm thinking due to this test with and without the fuse, I'm assuming the circled section is most likely where the problem is.

author: ZGoode
author_rank: Frequent Contributor
timestamp: July 13, 2024, 05:27:08 am
content: After making a replacement for the U1 (1813-0255) and replacing the transistors that tested bad with my DMM I have successfully gotten the 4277A to turn on. The analog section isn't working, so I need to figure that out, but this is a step in the right direction.
HP 4284a / HP4285a Help - Page 1
Forum section: electronics / repair

author: Nicklinux
author_rank: Newbie
timestamp: April 18, 2022, 01:49:54 am
content: I need help fixing the 'CALIB CSUM ERROR'. Thank you!

author: picburner
author_rank: Frequent Contributor
timestamp: April 18, 2022, 01:24:13 pm
content: There isanother personlooking for this program but there seems to be no answers for now.I have a 4285A and I would also like the 04285-65002 version for my instrument.I also tried to look in various programs forHP9000but this is a very specific software that is difficult to find among common computer programs.Too bad, because it would be enough to have the Basic listing to be able to translate everything into Python or another language manageable by modern computers.I dumped all the instrument's memories, U12-U24 eeprom included, but belonging to a 4285A I don't think they will be useful to you.

author: bsdphk
author_rank: Regular Contributor
timestamp: April 19, 2022, 11:33:48 am
content: Which CPU is used in these instruments ?You could disassemble the code to find out what the CAL checksum is and how to set it.(The ROM checksum is something entirely different)

author: picburner
author_rank: Frequent Contributor
timestamp: April 20, 2022, 06:41:29 am
content: The 4284A/4285A cpu is a Motorola MC68000 (in your case it is produced by Hitachi).The Fujitsu MB654810U is supposed to be an ASIC instead.Edit: I found the old MB65xxxx family datasheet

author: picburner
author_rank: Frequent Contributor
timestamp: April 22, 2022, 06:09:18 am
content: I found a post from a HP-Agilent-Keysight-equipment@groups.io user who owns (owned?) the 4284A adjustment program.But the post is four years old, I tried to contact him but I didn't get an answer.

author: kam
author_rank: Newbie
timestamp: June 11, 2025, 01:18:02 am
content: https://hpwiki.org/_media/service_notes:4284a-13.pdfHP Service NoteThe message "SCANNER DATA CSUM ERROR" is displayed with Option 301.
HP 4291B Repair - Page 1
Forum section: electronics / repair

author: JoeyDeng
author_rank: Regular Contributor
timestamp: March 03, 2025, 03:25:05 am
content: Hello,I got this instrument and finished repairing its A2 regulator. Now it is able to enter the whole system, and I can follow the service manual to troubleshoot the other parts of it.But some errors occurred while doing the self-test:CAUTION: PHASE LOCK LOOP UNLOCKEDA6 test failed...After following the service manual, I tested 2 2 x1. It showed a gain error, so I connected the A6 board to the A3A1 and tried to test 2 3 x1, but an error occurred. All these signs indicate that the A6 AFE board is dead. According to the service manual, I need to replace the A6 board...But this is an ancient HP instrument, and all its parts are discontinued. So, I need to repair this AFE board, but I don't have the schematic or further details about it. :'(Any ideas are welcome, so please let me know if you have any ideas for repairs.

author: JoeyDeng
author_rank: Regular Contributor
timestamp: March 03, 2025, 03:27:31 am
content: The picture of A6 AFE board. If anyone can share this PCB schematic, I'd be grateful.

author: JoeyDeng
author_rank: Regular Contributor
timestamp: April 04, 2025, 02:28:50 pm
content: I successfully repaired the 4291B. The main issue stemmed from the Y-gain controllable amplifier.
-hp- 438A with no display and unresponsive front panel - Page 1
Forum section: electronics / repair

author: 0culus
author_rank: Super Contributor
timestamp: November 17, 2019, 09:03:47 pm
content: Hi all,Recent auction score. An otherwise nice condition 438A dual sensor power meter. Cal sealed when I received it so I don't think anyone did any funny business. Symptom is that the unit powers on, but the display is dark and the front panel is otherwise unresponsive. I've been working through the troubleshooting and service sheets from the manual. So far I've determined:* Power rails are nominal* +5V display enable clock is not present at A9TP1* Test modes using the binary rocker switch on A3 seem fine. Kicker: display lights up and passes all the display test modes perfectly. Front panel responds to keypresses for the manual display test, but display enable clk still missing at A9TP1.* Signature analysis with my 5006A shows that the signatures for U21 do not match the manual values for either type of A3 board. U21 may be dead.* Signature analysis of U8 in free run mode is impossible, as the values are unstable. No idea what's up with that.* RAM backup battery is probably dead....will get a few more in an upcoming DigiKey order.* No GPIB communication seems to work.Bottom line is that I'm getting stumped on where to go next. Anyone else have troubleshooting experience with these units? I have tried reseating connectors and boards, no dice. I suppose it should be easy enough to find a donor and rob the ICs from it. Just want to make sure I'm not missing something obvious.Thanks!!

author: 0culus
author_rank: Super Contributor
timestamp: November 18, 2019, 01:36:35 am
content: Update: I dove into the signature checks for service sheets 1-4, and I believe I may have narrowed the problem down to U19, which is a Motorola MC68B09P (HP part number 1820-2624). Fortunately, it's socketed. Tried reseating but didn't have any effect.

author: Tony_G
author_rank: Super Contributor
timestamp: November 18, 2019, 02:27:43 am
content: Is that just a 6809 micro? Quick check on the bay shows a bunch available for US$7. There might also be something socket compatible that is still just a 6809.https://www.ebay.com/itm/5pcs-MC68B09P-Motorola-DIP-40-/173280778698TonyG
HP 48GX weird boot loop problem - any ideas? - Page 1
Forum section: electronics / repair

author: wmundstock
author_rank: Contributor
timestamp: August 04, 2022, 05:41:10 pm
content: Hi All.Here is a weird problem on a HP48GX.https://youtube.com/shorts/gmMI6rGGFSUHave you ever seen something like this?Any ideas of what the problem might be?I am thinking could be a problem with the contacts of the keys. Maybe some solder broken...If I boot a working calculator and get to that screen where it asks for the memory reset, when I click any buttons I get that beep.If I move or twist the calculator while its beeping I notice some slight variation in the frequency of the beeping.The problem is that these beasts are very hard to take appart and even harder to bring back together... any ideas?Thank you
HP-50G calculator - trying to replace rubbery sheet under keyboard - Page 1
Forum section: electronics / repair

author: Dave3
author_rank: Regular Contributor
timestamp: October 22, 2024, 06:19:24 am
content: We have an HP 50G calculator and some keys will not register. TWO PROBLEMS1. Dowels punched a few holes in black rubber sheet under the keys2. A few keys broke* How keys work - Each molded plastic key has one dowel underneath. When one presses the key, the dowel activates a dome switch.There are a few sheets beneath the keys:- Thin black rubber sheet (DAMAGED)- Paper/metal sheet (Undamaged)- Dome switch plate (Undamaged)PROBLEM 1 - some dowels have punched through the black rubber sheet. So the dowel just goes into the sheet but does not press down the dome switch. So the keypress is not registered.PROBLEM 2 - each key has two legs connected to a frame. Some of the legs are broken and some look like they are about to break. The calculator case is stamped "ABS"; the keys seem to be made of the same or similar material. I have seen a few people suggest a dab of epoxy on each leg. The orange/white/yellow keys are more robustly designed as you can see in the photo.Any ideas to repair or replace the rubber sheet & broken plastic keys?
Hp 5223L and Hp 5233 l Counters service manual - Page 1
Forum section: electronics / repair

author: vasi_ro
author_rank: Unknown
timestamp: March 04, 2020, 08:34:25 pm
content: HiI'm looking for service manual of Hp5223L and hp5233L.Thanks

author: madao
author_rank: Frequent Contributor
timestamp: March 05, 2020, 08:51:13 am
content: Artek Manual have this manual.http://artekmanuals.com/manuals/hp-manuals/I have also 5233L, it had wreid fault. Gate-control-ciruit dies sometimes, but always, if i lift it at running state. (Cause: poti leg is very near to bottom case , lift -> short, fixing with duck tape)Greetings matt
HP 5300B Measuring System Power Supply Whine - Page 1
Forum section: electronics / repair

author: Proton Peasant
author_rank: Newbie
timestamp: July 22, 2021, 03:49:36 am
content: Howdy folks,I purchased a HP 5300B with a 5308A 75MHz frequency counter (non-op) with the intention of repairing it and giving it a home on my bench.There is an audible whine coming from the power supply area of the 5300B, so I checked over the power rails, electrolytics and tantalums.I did have to replace a few, but it made no difference.So I found a PDF of the manual (available through Keysight), and stepped through their troubleshooting flowchart.They even make mention of the whining, so it apparently is a somewhat-known issue.These units have a blocking-oscillator based PSU, with some half-wave rectification to give +/- 17V, +/- 5V, and +3.5V.In the flowchart one of the tests is to apply +6V across the filtering capacitor and probe the collector of the switching transistor.When I performed this I found almost double the peak-to-peak amplitudes specified (see image below).Pulling the transistor and testing it with a cheapo component tester didn't raise any red-flags, though.I continued through the power supply checks in the manual, testing nearly every component mentioned out-of-circuit to no avail.Either the trouble is more subtle than expected or I bought a lemon.Does anyone have any ideas or experience with the 5300B measuring systems?If there are any other details that would be helpful, let me know.Manual via Keysight:https://www.keysight.com/ca/en/assets/9018-05900/user-manuals/9018-05900.pdfAttached are:- a picture of the circuit board with the power supply section outlined in red- A capture of the blocking oscillator transistor collector voltage (5V/div, 0.1mS/div)- PNG of the power supply schematic, again the full manual can be had through the Keysight website.Best,Proton

author: KE5FX
author_rank: Super Contributor
timestamp: July 22, 2021, 06:03:28 am
content: I'm not familiar with the 5300B system, but that hardware will lookveryfamiliar to anyone familiar with HP's atomic (Rb and Cs) standards from the same era. Short answer: yes, they make some racket, and it's almost certainly normal if the voltages are in spec.Have you checked the ESR of all of the filter caps associated with the circuit? That could account for some of the noise.

author: lombster
author_rank: Newbie
timestamp: May 08, 2025, 02:12:46 am
content: Any chance you've figured out what the issue is?

author: coppercone2
author_rank: Super Contributor
timestamp: May 08, 2025, 02:15:57 am
content: always check the disk capacitor they go brezerk on the modern power gridhums are transformer, annoying high pitch shit may very well be the ceramic disk capacitor near the transformer.