HP 34970A Ser.Nr. US37007297 repair help needed -FIXED - - Page 1
Forum section: electronics / repair

author: Spectrum
author_rank: Regular Contributor
timestamp: November 17, 2020, 01:28:37 pm
content: Hi, I am writing from Italy and my English is not so accurate. I have this measuring instrument which needs repair.At the start there are 5 errors, in particular:1) 742 CAL DATA LOST: DCV CORRECTIONS2) 743 CAL DATA LOST: DCI CORRECTIONS3) 744 CAL DATA LOST: RES CORRECTIONS4) 745 CAL DATA LOST: FRES CORRECTIONS5) 746 CAL DATA LOST: AC CORRECTIONSI read that these errors refer to the EEPROM memory which, in this unit is marked 24C04-S and is close to the back-up lithium battery that (battery) I have already replaced.Furthermore, if I perform the extended test, I find over 10 errors: the same as the start twice repeated and a new one marked with the code 621 SELT TEST:AC RMS FULL SCALEAlmost all the components are manufactured in 1997, browsing through the various menus I could read:REV 06-01-02PWR ON LASTDMM ENABLEDCAL SECUREDHOW CAN I attempt the repair? Does the 24C04-S need to be programmed? Where can I find this complete firmware component? What is the error 621 due to?Could someone who knows this measuring tool well help me?Thanks for the answers. Stefano (Steve)

author: pico61
author_rank: Contributor
timestamp: November 18, 2020, 11:29:46 am
content: You have to download the HP34970A Service Guide from Keysight website. The link:https://www.keysight.com/main/techSupport.jspx?cc=IT&lc=ita&nid=-33261.536881544&pid=1000001313%3Aepsg%3Apro&pageMode=PLI looked at the manual but the errors you indicate are not reported. There is only the 621Fortunately in the service guide there are all the wiring diagrams to try a repair.

author: Shiv
author_rank: Regular Contributor
timestamp: November 18, 2020, 12:08:43 pm
content: Quote from: Spectrum on November 17, 2020, 01:28:37 pmDon´t hestiate too much with the cal errors, if the memory was erased or factor lost, you will keep this error until unit is calibrated and adjusted.The fisical damage could be the failed self test...621: AC rms full scale failed This test configures for the 100 mV acrange. The 1 mA ohms current source is switched on the charge theac input capacitor A4C301. This produces a pulse on the output of therms-to-dc converter which is sampled 100 ms after the current isapplied. A 20 ms A/D measurement is performed and checked againsta limit of 10 V ± 8.5 V into the ADC.Looking at SM schematics, I would check +-15V (wich powers the OP apms) and try to follow back the signal from C301 to the amplifiers...If that looks ok, replace nvram, initialize and calibrate it.Look at this:https://www.eevblog.com/forum/testgear/hp-34970a-error-741-fix/

author: Spectrum
author_rank: Regular Contributor
timestamp: November 18, 2020, 01:30:56 pm
content: Thanks so much for answer. The voltages are OK, for the rest I will test in labo next time.For first I discovered there are two FRAM, one in the main and one in the DMM, is it right ?Is the DMM module the one positioned above the main next to the slots and above the back up battery?Above my IC there is written 24C04-S, is it a FRAM ?I just bought online nr. 10 24C04-S, I think the package will be here in 10 days

author: Shiv
author_rank: Regular Contributor
timestamp: November 18, 2020, 10:17:21 pm
content: Oh...I have read the first post again and I see you replaced the battery, some of this old boys have a special procedure to do it (power inputs, jumpers or so...)Before doing more, read this:https://community.keysight.com/servlet/JiveServlet/download/63858-1-5176/Error%20740%20Series%20for%20fix%2034970A.docI don't know if was before the fails or the battery change, it may be just power loss and the memories are ok.I would try it without replace it.But be sure you have the proper equipment to do it.(Manual requires 5700A, but maybe a 3458a and various stable sources will make an approach)

author: Spectrum
author_rank: Regular Contributor
timestamp: November 19, 2020, 07:40:05 am
content: Hi,before battery change the fails were the same...and the old battery (SANYO) was 2,4 or 2,7V not so bad. With new battery nothing has changed.Could it mean anything?This afternoon, if I have time, I try to make some measure about C301 and amplifiersthanks for the availability shown

author: coromonadalix
author_rank: Super Contributor
timestamp: November 19, 2020, 11:30:09 am
content: the battery did not leak on the board ? no corroded traces ? are all chemicals okay, leaks corrosion ?

author: Spectrum
author_rank: Regular Contributor
timestamp: November 19, 2020, 11:58:43 am
content: No leak or acid traces. It was the original one (1997) but still intact

author: Shiv
author_rank: Regular Contributor
timestamp: November 19, 2020, 02:25:16 pm
content: Quote from: Spectrum on November 19, 2020, 07:40:05 amDon´t worry, I don´t mean the cause was the battery change, but if was it, there is no need to change memories, only to clean it and write again.If the failures was before the battery change and was 2.x V, is probable that was bad memory instead of memory out of power.You would probably need a new ones. (follow the entire procedure instead of start from cleaning)I would start ignoring ERR 621, is possible that get this error from going out of adjustment range (fine adjust at selftest), with memory lost, it can happen.NOTE: I would do that just because I have equipment at work to factory adjust it, I prefer adjust without change nothing and check if works.At home without equipment, I´ll do it otherwise, check for faults to try to get the memory intact until no more options available.NOTE2: My english is more horrible than yours and here we are... understanding us....

author: Spectrum
author_rank: Regular Contributor
timestamp: November 19, 2020, 04:51:59 pm
content: OK thanks Shiv. I am waiting for new 24C04-SQuote from: Spectrum on November 19, 2020, 07:40:05 amSorry, no time, I hope tomorrowQuote from: pico61 on November 18, 2020, 11:29:46 amit would be nice to have the schematics, but neither in the service manual nor in the user are there. Do you know where is possible to find them ?

author: coromonadalix
author_rank: Super Contributor
timestamp: November 19, 2020, 06:11:32 pm
content: the 34970 service manual is available on the web check at KO4BB website too

author: Shiv
author_rank: Regular Contributor
timestamp: November 20, 2020, 11:10:45 am
content: Quote from: Spectrum on November 19, 2020, 04:51:59 pmHere it is:https://drive.google.com/file/d/1zbxCo8pLu3gEZDXRaVp-ABRcauAjqjLf/view?usp=sharingThere are the adjusment procedures too, check it.

author: Spectrum
author_rank: Regular Contributor
timestamp: November 20, 2020, 11:45:32 am
content: Wonder, thanks a lot

author: jogri
author_rank: Frequent Contributor
timestamp: November 20, 2020, 12:06:22 pm
content: I have a 34970A that experienced the same failure, so i am rather certain that the second FRAM is dead. Not the one near the battery, but the one on the DMM module (that's the thing you have to remove to get to the battery). Start the 34970 without this module (perfectly okay to do this), it shouldn't give you the 740-errors.The FRAM (yes, those are FRAMs) work without a battery, so this isn't the problem here. You can try to programm the new FRAM with the content of the old, but sinces this FRAM is dead it is probably corrupted (happened to mine). So your only realistic option is to bite the bullet and install a clean FRAM and initialize it via the GPIB commands. There's only one small problem: The instrument is proper f***ed without calibration, mine was around 2-3% off on nearly everything.(And you should replace the battery while you're at it)Btw, the 24C04 FRAMs can be an absolute nightmare to program with a programmer, so just don't bother with that, install clean ones and run the two initialization commands.Protip: Make absolutely sure that the new battery can't get lose (by cracking the solder joint) as this will result in a "dead" 34970: Won't power on and troubleshooting this can be quite time consuming as nothing appears to be broken (i'm speaking from experience...).

author: Spectrum
author_rank: Regular Contributor
timestamp: November 20, 2020, 12:42:26 pm
content: Thanks jogri is all quite clear, only the last part I did not understand completely."" Protip: Make absolutely sure that the new battery can't get lose (by cracking the solder joint) as this will result in a "dead" 34970: Won't power on and troubleshooting this can be quite time consuming as nothing appears to be broken (i'm speaking from experience...).""The new battery has soldered in his site, definitely.I will do a new calibration, I have some reference voltages and resistances. A problem will be initialize it via the GPIB commands, never done before...

author: jogri
author_rank: Frequent Contributor
timestamp: November 20, 2020, 12:51:23 pm
content: Quote from: Spectrum on November 20, 2020, 12:42:26 pmThat's what i thought when i installed a new battery in my unit... Only to have it shaken loose by who knows what after a few months of constant use.The initialization is the easy part, just get the TekVISA software and use the Instrument manager to send a GPIB command to it. Btw, this thing requires an AC signal in the kHz range for the calibration, so you'll need some sort of AC calibrator (mains + Variac won't cut it, tried that).

author: Spectrum
author_rank: Regular Contributor
timestamp: November 20, 2020, 01:22:19 pm
content: I have an Agilent 82357B USB with software, but never used...I have a Bradley 192 (Oscilloscope Calibrator), it is a stable voltage source, DC (from 5 mV to 120 V), AC (only 1KHz square) and frequency (impulse). If it is not enough, I have some function generator (HP33120 ecc..) so somehow I'll doWhat do you think about Error 621 AC rms full scale failed ?

author: Shiv
author_rank: Regular Contributor
timestamp: November 20, 2020, 03:33:55 pm
content: Quote from: Spectrum on November 20, 2020, 01:22:19 pmThat isnt enought for that calibration.. .Bradley has 0.25% in DC mode, cool for 2% scopes, but not for this.DC can be done with a clean ps and a well calibrated DMM (8.5 digits... Aka 3458)AC is difficult to get it without an ac calibrator or a lot of things.Tipically: 5700A... Maybe 5500A.I doubt if a 33120 with a 3458a could do the job...Maybe, at least for home use.Resistance: maybe with a decade and a well calibrated DMM..Same with current.Too difficult on AC mode without a nice standard

author: coromonadalix
author_rank: Super Contributor
timestamp: November 20, 2020, 04:58:16 pm
content: should be barely enough to check if the 34970 respond and get rid of the errorsand if its is, send it to a cal lab

author: Spectrum
author_rank: Regular Contributor
timestamp: November 20, 2020, 07:36:57 pm
content: Let's start with fixing the device, which is the important thing, then I'm sure to do a decent calibration ... probably not at 2ppm, but to be used accurately enough at 0.01%I can also have for DMM a 3458A, 34401, Kethley 2001 and Prema 5017 with short and good cables, it is not a problem for me to find the correct value, but to have a stable, non-variable standard. Obtained this, I can measure it exactly. The Bradley, after the correct warm-up, is sufficiently stableHowever, nothing prevents me from having it calibrated, but I cannot bring to calibrate a faulty or out of specification device

author: jogri
author_rank: Frequent Contributor
timestamp: November 20, 2020, 08:19:44 pm
content: Quote from: Shiv on November 20, 2020, 03:33:55 pmNo, it needs something like 300 V @ 10 kHz for the full-scale cal. You could maybe use it for the 10 V range, but that's it. And just forget the AC current cal, it needs 1 kHz.In regards to the 621 fault: Haven't had it personally, but i'd check the responsible capacitor as well as the formed pulse.Quote

author: Shiv
author_rank: Regular Contributor
timestamp: November 21, 2020, 09:30:46 am
content: Quote from: jogri on November 20, 2020, 08:19:44 pmFor "home use" I mean "barely clean errors"...Just check nothing is broken and can be adjusted by comparing with a 3458a...For hi V AC... A lot of things...For ACI... I don't know how...

author: Spectrum
author_rank: Regular Contributor
timestamp: November 21, 2020, 12:46:16 pm
content: Quote from: jogri on November 20, 2020, 12:06:22 pmCorrect, no errors wtihout DMM, when I will have the 24C04-S I try to change this for first.The voltage are OK only the +18 V is about +19For error 621, by a quick check, the C301 is OK and the amplifier 301 is supplied (+/-15V) and seems work. However, it is better to check more accurately

author: Spectrum
author_rank: Regular Contributor
timestamp: November 24, 2020, 08:49:40 pm
content: Hi,replaced the new 24C04-S in the DMM but the errors are always the same. The 24C04-S is supplied. I need to initialize the unit or something is wrong anyway ?

author: jogri
author_rank: Frequent Contributor
timestamp: November 24, 2020, 09:55:52 pm
content: Yes, you have to initialize the new FRAMs by sending the two commands via GPIB. Do that, then restart the unit and the errors should be gone (you'll probably still get a date/time lost error on the first start, but that's okay).

author: Shiv
author_rank: Regular Contributor
timestamp: November 25, 2020, 10:11:35 am
content: Quote from: Spectrum on November 24, 2020, 08:49:40 pmhttps://community.keysight.com/servlet/JiveServlet/download/63858-1-5176/Error%20740%20Series%20for%20fix%2034970A.docHere are the commands you should send to 34970AYou can do it with vee, labview or another software like NI-MAX or MetCal

author: Spectrum
author_rank: Regular Contributor
timestamp: November 25, 2020, 10:53:24 am
content: Thank guys, I have an Agilent 82357B USB and I installed the software from owner CD. It is the first time I do that, so I need help if I get some issue.The VEE I read from the link is the same sw I can find in the Agilent's CD ?This afternoon or next I try to connect my PC to the unit by 82357B and tell you news

author: jogri
author_rank: Frequent Contributor
timestamp: November 25, 2020, 11:34:02 am
content: Quote from: Spectrum on November 25, 2020, 10:53:24 amLet me guess: Brandnew one for 80 bucks from ebay? It's a fake, i recommend that you download the software directly from Agilent/Keysight (the software from the CD is probably an older version, but that shouldn't really matter). (Those fake GPIB adapters work 95% of the time, so don't worry there, just keep in mind that it might have some weird quirks)But yeah, install a software of your choice (Agilent VEE, NI-MAX, TekVISA, etc) , connect the 34970 to the PC and start it (look at the display, it will show you its GPIB adress when it starts) and then search for instruments. The 34970 should be there, you can make sure that it communicates by querying the string "*IDN?" (without the "") (there should be a Query, Write and Read button, use the "Query"). That command works with all GPIB devices and gives you the name/ID of it back. In your case, it should return "Agilent, 34970A".If that's the case, it's time to send the two commands: First, write "DIAG:POKE 15,0,0" and hit "Write", then write "DIAG:POKE 0,0,0" and hit "write". After that, restart the 34970 and follow the rest of the procedure from the document.Protip: Remove the cards of the 34970 before you do this.

author: Spectrum
author_rank: Regular Contributor
timestamp: November 25, 2020, 07:47:52 pm
content: Hi,I don't know where my 82357B come from. After read your message, I got dismantle it and inside the pcb is Agilent marked (serigrafy) also the IC are marked Agilent. If it is a fake, is really well done.Is this a fake ?https://www.ebay.it/itm/New-In-Box-HP-Agilent-82357B-USB-GPIB-Interface-High-Speed-USB-2-0/264258218741?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649Mine is not Keysight marked, it is older...USB 2.0 but Agilent marked. It stood still for a long timeBefore dinner, I quickly tried to connect 34970. No result, no instrument connected, but it was set for RS-232....when I realized it was late and I went to dinner

author: coromonadalix
author_rank: Super Contributor
timestamp: November 26, 2020, 01:59:57 am
content: For an original usb gpib, you're supposed to have copper paint on the shells and have some can be been seen near the two screws when they enter the shell, thats a good start to know if its genuineAnd i think you can do a serial number search on/at Keysight to check/validate it ??

author: Spectrum
author_rank: Regular Contributor
timestamp: November 26, 2020, 08:46:25 am
content: No copper paint

author: Spectrum
author_rank: Regular Contributor
timestamp: November 26, 2020, 06:07:03 pm
content: I opened Keysight VEE Pro, click Instrument Manager, then Find and it appears in the window GPIB0 and bottom newInstrument(hp34970a@GPIB0::9::INSTR).Now I can do anything else, I do not have the windows I can see in the link "Error 740 series for fix 34970A".If I click something else, it is appears a blue message in the bottom "An object cannot be placed in the workspace (press Esc to cancel)"In the unit nothing change, you can see Insert Card and red light Error.

author: Shiv
author_rank: Regular Contributor
timestamp: November 27, 2020, 12:09:33 am
content: You can also do it from connection expert:Select board, scan for instruments, select yours and interactive I/O.

author: Spectrum
author_rank: Regular Contributor
timestamp: November 27, 2020, 09:51:44 am
content: Thanks Shiv and yes I did it by Keysight Connection Expert 2020 and Keysight Interactive IO. For first I unsecured the unit by front panel, then send and read this commands:-> *IDN?<- HEWLETT-PACKARD,34970A,0,6-1-2-> DIAG:POKE 15,0,0! VI_ERROR_TMO: A timeout occurredVisa ErrorCode: 0xBFFF0015 (-1073807339)<--> DIAG:POKE 0,0,0! VI_ERROR_TMO: A timeout occurredVisa ErrorCode: 0xBFFF0015 (-1073807339)<--> SYST:ERR?<- +745,"Cal data lost: FRES corrections"In the display I can see the ADRS and RMT leds light on and of course INSERT CARD and red light ERROR, nothing else...24C04-S or interface 82357B do not working ?

author: Shiv
author_rank: Regular Contributor
timestamp: November 27, 2020, 11:04:25 am
content: Quote from: Spectrum on November 27, 2020, 09:51:44 amDid you send the POKE commands as "write" or as "query" ? you must send it as writeThey shouldn´t reply, so the timeouts are because the PC keeps waiting for an answer. (Query)The 82357B is working, it writes and reads (*IDN? and SYST:ERR? are writing and reading ok)Follow the entire procedure step by step:https://community.keysight.com/servlet/JiveServlet/download/63858-1-5176/Error%20740%20Series%20for%20fix%2034970A.docAfter sending PUKE commands, the memory is initialized, so the CAL DATA LOST should be normal.You need to check if calibration procedurement is working and the memory can be written/readed by the 34970A.To do this, after puke, go to the service manual and make the first steps of adjustment procedure.It´s just Zero adjustment, you only need to short terminals.Once it´s done, the cal data lost should dissappear and is time to send the 34970 for adjustment with a BIG NOTE saying all cal factors are lost, so tecnician will go directly to adjustments and don´t think is a broken unit.

author: Spectrum
author_rank: Regular Contributor
timestamp: November 27, 2020, 11:50:47 am
content: Hi, I have no Write or Query but Send Command, Read Response, Send and Read.Anyway after some attempts the errors codes 700 disappeared, well done. Thank youI also tested this old 82357BNow, during the extended test, error 621 remained, plus error 620 and 622I think some OP-AMP has gone...

author: Shiv
author_rank: Regular Contributor
timestamp: November 27, 2020, 12:57:36 pm
content: Query = Send and Read.Write = SendQuoteDid you do the zero adjustment?If not, try to do it.If yes, I would try to check A4 k103 relay for bad contacts. (fisical switch is more likely to fail by age.)After that, follow the signal through U301,U304,U305, U306, U312,U307 and U308

author: Spectrum
author_rank: Regular Contributor
timestamp: November 28, 2020, 02:39:36 pm
content: Hi,Zero Adj done, no results.All three relays (K101,102,103) seem to me to be faulty with alternate functioning.I have exactly the same but with 12V coil, not 3V. I have nothing at 3VHowever they seem to me of poor quality (even if OMRON) considering the cost of the instrument.Now I am going to looking for.. OMRON G6SU-2 3VDC. Probably is better to purchase a supply for future repairs.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 28, 2020, 03:53:13 pm
content: i dont think youre doing good repairs at some point, Omron Does make good relays, do proper analysis before thinking this and that, follow the service manual properly and follow signal pathsThe meter got busted in some ways, you have to check many things as you know, dont assume things and do the opposite by changing too many parts for nothing, stay focusedIf they where this bad (relays) it would not have been put in it

author: Shiv
author_rank: Regular Contributor
timestamp: December 01, 2020, 02:06:37 pm
content: Quote from: Spectrum on November 28, 2020, 02:39:36 pmI allways try to fix relays before replacing.Little more tension than rated on square signal at coil.1 kHz and let it go for a while.

author: Spectrum
author_rank: Regular Contributor
timestamp: December 01, 2020, 02:34:53 pm
content: I will try, thanks

author: Madmanguruman
author_rank: Contributor
timestamp: December 04, 2020, 09:46:09 pm
content: Can confirm that the 3V lithium battery doesn't affect the calibration data of the 34970A - it's only used to back up scanned data / channel configs. I've replaced at least 5 of these so far.I've also noticed that on a few DAQs, self-test errors related to analog parameters self-corrected as a function of this disassembly/reassembly - perhaps the contacts between the boards would become a bit corroded (some of these DAQs were 20+ years old) and just removing/reinserting them would clean the pins enough to make them 'work'.(It's a little sad that these units are being discontinued in June. The new DAQ970A is decent enough, but hey. Nostalgia.)

author: Spectrum
author_rank: Regular Contributor
timestamp: December 05, 2020, 01:50:01 pm
content: Ja, battery doesn't affect, you must replace the FRAM 24C04-S (U450). Unfortunately no oxide in the contacts.Come back to my unit, relays regenerated and replaced for safety with those of card 34901. The three errors are still there.The DMM doesn't measure AC Volts.I followed the signal through C301, R301, R302, U301, U304, U305 ... but I am not able to evaluate if the signals I see with the oscilloscope are the correct ones.At the input there are 15Vac 50 Hz (DMM in autorange). In U301A pin2 there is a half wave, which becomes smaller at pin6. Through U304C, I find this signal on U305A pin3, in pin 2 I find a square wave with some spike during the flat, after that I didn't go ...Could the fact that there are 3 errors, all the possible ones for the AC, help to identify the fault?thanks for your patience

author: Spectrum
author_rank: Regular Contributor
timestamp: December 06, 2020, 01:35:17 pm
content: in U305 (perhaps also in U312) the -15V is not present (-15B). Probably the zener CR304 and the C314 are knocked out. I have no a BZX84C3V3 (SOT23) thus for a test I will mount a traditional 3.3 zener.

author: Spectrum
author_rank: Regular Contributor
timestamp: December 06, 2020, 06:03:02 pm
content: Yeesss, FIXED.Temporarily mounted a BZX55C3V3 (old style, not smd). Extended self test results PASS ... The AC reading works in all ranges but is seriously out of calibration (14.5 Vac instead of 15.2). As soon as I have the BZX84 available, I will replace it and proceed with calibration. The power supply voltage of the U305 / U312 is + 15.2 pin7 and -14.60 pin4 (a little low). We will think about it when I will have the final components, a couple of weeks.Thanks everyone for the help

author: Shiv
author_rank: Regular Contributor
timestamp: December 06, 2020, 10:17:18 pm
content: Quote from: Spectrum on December 06, 2020, 06:03:02 pmGood to hear that!I feel like it was mine!

author: Spectrum
author_rank: Regular Contributor
timestamp: December 07, 2020, 09:55:55 am
content: Ja thanks Shiv.I saw earlier that a 34401A also had a problem with these Z-diodes and related C. Obviously it is one of their weakness.In summary, this unit had 4 issues:- tired back up battery 3V- inefficient relays- FRAM 24C04-S (U450) of calibration data KO- power supply OP-AMP (U305, U312 etc.) due to Z-diode CR304 (BZX84C3V3) KONot bad, all in one shot

author: coromonadalix
author_rank: Super Contributor
timestamp: December 07, 2020, 03:18:46 pm
content: glaid it work now

author: Madmanguruman
author_rank: Contributor
timestamp: December 16, 2020, 06:27:37 pm
content: I would also consider replacing the fan for such an old DAQ. They're easily available from Digi-key or other vendors.https://www.digikey.com/en/products/detail/delta-electronics/AFB0405LA-A/5799904You'll need to crimp on two Molex header inserts (or cut/solder onto the existing fan header).

author: Spectrum
author_rank: Regular Contributor
timestamp: December 16, 2020, 06:33:58 pm
content: Ja why not, the fan that's there now is noisy