HP 3458A - Fails Slave Test - Convergence - Page 1
Forum section: electronics / repair

author: Ade911
author_rank: Regular Contributor
timestamp: April 21, 2023, 01:38:26 pm
content: Hi team,I have an HP5458A that has started to fail the bootup self test - Fails Slave Test - Convergence.The manual suggests this relates to A1 PCB DC Input. Ive had a probe around and I've noticed that Q106 is on which is fine but the source voltage slowey drifts from zero to above 10volts over time. I did remove Q106 which stopped the voltage rise so it was replaced just in case it was leaking. However the fault is still there so before changing any other parts I did wonder if any one else could recommend where to look.Any support and advice would be most welcome.Many thanks,Ade.

author: Swake
author_rank: Frequent Contributor
timestamp: April 22, 2023, 06:09:22 pm
content: Is that thing trowing an error 202?The 'internet' suggests several things:Jumper PCBA on board A1 is missing or configured wrongly. It must be placed in position 'normal' over pin 2 and 5.If that is check then proceed with an autocal.

author: Ade911
author_rank: Regular Contributor
timestamp: April 23, 2023, 08:10:47 am
content: The jumper is in the correct position, autocal fails. probing TP11 on A1 you can see the voltage jumping most times to 10V, then 1v, cant read the 0.1 on the scope in the time given but still then after it fails the test. After doing this a few times I now have a further error ACAL DCV, OHMS R. I dont know if its a temperature issue or something is failing the more I test it. I still get when checking the error code202,"HARDWARE FAILURE -- SLAVE TEST : CONVERGENCE

author: Ade911
author_rank: Regular Contributor
timestamp: May 05, 2023, 11:47:16 am
content: Hi , I really need some help please.I started with Fails Slave Test - ConvergenceI now have this plus ACAL DVC, OHMS R error.Dr David Partridge on xxx@groups.io suggested i try a Autocal ACAL DCV which i tried but still i have the above errors.Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again.Ive checked the Convergence circuit with my very limited understanding of the circuit. FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working.As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in]After powering the system back up I still have the same issues.Has anyone seen these issues, can some one please direct me to where I maybe should be looking as obviously Im in the wrong area.The unit was working fine several months ago, the was a bad connection between -20v (-21v) and the power supply but that was resolved by reseating P3.All voltages recorded on the schematics have been checked and are close to the spec [maybe my old fluke meter needs calibrating as well]Any advice and support will be most welcome or direction to any manuals explaining in detail how the circuit works would be very much appreciated.

author: Ade911
author_rank: Regular Contributor
timestamp: May 05, 2023, 04:44:32 pm
content: This afternoons update.Still shows Fails Slave Test - Convergence on power onAfter finding -20v missing through P3 to PCB A1 i reset all the DIN cables , magically the system started to sample more when testing DCV.Autocal DCVSample 10V OKSample 1V OKSample 0.1V random samplesSample Zero DCV 100Sample Zero DCV 1KVClick of RelaysScreen shows VDC ResetACAL OHMS REQUIREDSample ACAL OHMS 10KSample DCI 1/10uBeepScreen shows VDC Still has ACAL OHMS REQUIREDAny thoughts what to check next please

author: Ade911
author_rank: Regular Contributor
timestamp: May 06, 2023, 03:23:53 pm
content: Todays updateManaged to borrow an A1 bd, replaced and still the same problems.Should I replace the memory devices on the CPU board as they are rather old and maybe the batteries are dead.Support most welcome please

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 06, 2023, 04:11:08 pm
content: Hello,it's never a good idea to blindly change components on suspicion, especially not on the 3458A.The nvRAMs very probably have nothing to do with this error.Check their Date Codes, please. As well, provide Date of Production (DC on other components) for your instrument, so that we have the possibility to judge possible errors.This kind of error often relates to the fast comparators EL2018 on different boards, in this case I assume U142, or U181, less probable U405 on A3 ADC board.There's another of these comparators on the AC board.You get much better ideas what might be wrong on xdevs.com, please check his different repair articles (3 or 4?).At first, please make regular measurements in all modes, which fail and which work.Short NPLC and longer NPLC in DCV might have different behavior and might indicate a failure of said EL2028.You did not provide any details, how and when you got the instrument, if it was DOA, or failed after transport, or some usage time.If latter cases apply (vibrations?) then you should check all of these serial fiber optics interfaces, if they are properly stuck into their counterpart.Sometimes, some of these optical interfaces fail.Please make systematic failure analysis on this instrument, so not to increase your trouble.Frank

author: Grandchuck
author_rank: Super Contributor
timestamp: May 06, 2023, 04:15:55 pm
content: https://xdevs.com/fix/hp3458a/You are probably already aware of TiN's work ... but, just in case ...

author: Ade911
author_rank: Regular Contributor
timestamp: May 07, 2023, 12:37:13 pm
content: Thanks Grandchuck for the link, Ive started reading , truly amazing what was achieved.Dr Frank, thank you to for the support , you have so much understanding of these meters its truly outstanding.My initial problem relates to the understanding of the circuit, I thought HP would have a guide showing the flow of signals through the system but I couldn't find anything , only the amazing write up re the A/D and signal conversion.System history,Not sure how you confirm the age of the unit but I guess around 2001 due to the old labels on it.Managed to purchase maybe 5 years ago , upon trying to power on at that time I found the inguard board was burnt around CR11,CR12 maybe caused by the incorrect power setting from the previous owners. These were replaced and the system powered on, but due to travelling allot at the time it was switched off and left for 2-3 years.After getting more time power was reapplied to the unit, only to then me confronted by the smell of death from the input filter frying. This I replaced along with some of the large caps on the two power supply boards [ recommended on line to change ]Again due to time away the system was left off for another 2-3 years but now I have time to use more. The last time it was powered up the unit sampled correctly, passed all internal self tests so it was a surprise to be confronted with the initial error. when i switched it on again.I focused on A1 due to the manual fault finding recommendations by HP but as now proved there guidance note was incorrect I believe although its doing more now that before I changed the devices and re-seated all the interconnects so not 100% sure what helped.Ill trace the signal as you suggested around these devices , as nothing works , well I cant get the meter to read any values , is there a way to bypass the initial startup tests to be able to read values.Many tx Ade.

author: Grandchuck
author_rank: Super Contributor
timestamp: May 07, 2023, 01:47:48 pm
content: http://hparchive.com/Journals/HPJ-1989-04.pdf

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 07, 2023, 08:32:50 pm
content: you may read date codes from the nvRAMs and from any IC on A1, A5, etc.First will give you a hint about the sanity of the calibration constants, 2nd will give the age of the whole instrument. there also some stickers on stamps inside. The serial number as well gives a hint.. I have a table somewhere, to match production date and ser. no.If its really from 2001, like my unit, then 20 year old nvRAMs should be replaced.. save content of calram at firstThere's been a lot of recent damage inside the instrument... so that's unpredictable, what has happened.if the unit worked until recently, then I tight not have affected the comparators, which are unobtainium.these usually fail for very old units with high use in high temperature environment, due to heat death.check all the fibre optics. maybe the shift register chain is broken, I remember one instance.try to change NPLC to small numbers <1 , hopefully the instrument reacts to commands.BTW.: TiN / xdevs has most experience on the 3458A and really disassembled each and every part of this DMM.Anyhow, thank you for the compliments

author: Ade911
author_rank: Regular Contributor
timestamp: May 08, 2023, 07:45:28 am
content: I checked U181 and this looks fine,All signals are fine except pin 3 where it toggles only to 7v during a DCV cal then fails / stops sampling, or 10v when it does a little more sampling and the output jumps to 5v [plus relay clicks on].U142 , again I believe is ok, the output is toggling between 0 and 5v, however if I scope the input pin 3 the sampling fails  , its as if the system doesn't like the extra load, which is strange as its only a normal scope probe.You mentioned the shift registers , where or is there a guide explaining how they work [plus other sections, signal routs etc], i confess i didn't read all the HP Journal shared by Grandchick because it seems to focus only on the logic behind the A-D conversion process.OK , of to test the other items you mentioned,thanks againAde.

author: Ade911
author_rank: Regular Contributor
timestamp: May 08, 2023, 08:08:36 am
content: Dr Frank,Details on the Dallas chipsDS1230Y-1509538U 067285DS1220Y-1509547D 070606Not sure if that is the information needed to confirm the age.BTW , is there a procedure I can follow to download the stored data / replacement please.Many txAde

author: Ade911
author_rank: Regular Contributor
timestamp: May 08, 2023, 01:18:11 pm
content: updateSo I guess the dallas chips are from 1995 week 38 / 47 after watching videos about them, ill order replacements and hope you can clarify how i can download and replace.I also found an old communication from TiN re the TARM command, OMW , after doing this the meter came to life and did a few samples before stopping again [but it is repeatable]. With nothing connected im getting various voltages between +5.xxx and +10.xxx , If you do an autozero i then get +10.xxxxv.

author: Ade911
author_rank: Regular Contributor
timestamp: May 08, 2023, 04:57:50 pm
content: Todays updateonly samples if i manually trigger TARM command, no idea why.when i initially started to look inside i found the voltage on U100 pin 6 is slowly drifting up , its still doing it now. Unfortunately I damaged Q106 but was able to replace so didnt think any more about it, but today I find myself again back here as the signal DC_AD is slowly rising and is reflected on the screen [least I know the DAC is ok]screen readingsDCV volts ? +0.689 max then freezes - error message time out read A/D 108 [but it cant be the DAC]ACV mv samples for ever 1.945mv ACACV 000.081 and rising VACOHMS +0.VLD GOHMOHMS +OVL.D MOHM stops samplingOHMS +OV.LD KOHMOHMS +OV.LD OHMDCI nA 000.173DCI uA 0.000159 stops samplingDCI mA 0.0000248DCI A 0.0000135ACI uA 000.0434ACI mA 0.000286ACI A 0.000268FREQ 50.xxx HZData error matches system asking for DCV and OHMS calibrationAny support most welcome pleaseTx Ade

author: Kleinstein
author_rank: Super Contributor
timestamp: May 08, 2023, 06:52:03 pm
content: The convergance failure / salve test fail and hang up state point a little towards the ADC board (A3). Here known failing parts are the already mentioned comparators, the fiber link (e.g. loose connector) and also the worst case U180 failure.A drifting signal in the voltage reading mode cold be something like a porblem on A1 with the input path (e.g. relays or as TiN just had it with the protection resistors). A open path there can make the amplifier slowly dirft. As the readings in current and AC mode seem stable, this points in this direction. Of cause just an open input (e.g. switched to rear) could also cause drift and an overlaod reading with ohm tests.The odd trigger behavior could be as simple as a odd configuration still remembered in the buffered RAM.

author: Ade911
author_rank: Regular Contributor
timestamp: May 09, 2023, 06:41:22 pm
content: Kleinstein thank you for your feedback and advice. I want to believe that the A3 Bd is OK only because it does measure a value plus its expensive to replace.Plan of action,Purchase new memory devices and try to copy over the existing data.Break the loop on the A1 Bd and see where the rise in voltage is coming from around Q106, Q107, Q108.I read that the original FETS are obsolete, has anyone found an alternative device just in case one is leaking ?Many tx Ade.

author: Ade911
author_rank: Regular Contributor
timestamp: May 09, 2023, 07:13:38 pm
content: Sorry meant to ask, as the Dallas models are now obsolete which version should i purchase.Also what type of reader , programmer is recommended wih out spending mega bucks.Many tx Ade.

author: Ade911
author_rank: Regular Contributor
timestamp: May 15, 2023, 08:26:04 pm
content: UpdatePurchased a GQ-4x4 programmer , removed all Dallas devices and copied data to new ones , replacing in the meter , now suffer from needing all calibrations , not sure if the copy was OK although the programmer said they were - really confused over this. BTW the programmed sometime [if you programmed twice or ore] would randomly say there was a problem with the Dallas chips , not sure if others have had similar problems with these programmers.In parallel I found the output of U105 which drives analog switches on A1 was floating all over the place , what ever i tried on the input had no effect on the output so removed , need to wait for a new device but for now running LM709 which is not ideal but I dont mind as the out put which drives U104 is grounded anyhow so I could actually run without the device I believe at present.As suggested I also checked all the fibre connections which seem to work OK well I believe they do , scoping one end and the other the signals jump up and down at the same time.So now things get worse, the system was trying to calibrate DCV before I checked the fibre links, it was sampling but now nothing.It only samples when I activate TARM and in KOHMS although it shows overload.TP100 is also slowly drifting up to the supply rail voltage, Ive replaced U103, U108 and still no joy.The input to Q103 is stable , zero volts if i recall , if I remove U103 everything is fine and I don't see any drift so could it be the FET Q107 Q108 well not sure. As I don't have spare and Im not sure if we can get replacements - SOMEONE PLEASE CONFIRM IF IM WRONG as Im scared to remove them.Can someone please also confirm where the calibration 10V comes from as well , again I'm confused to know where its generated and fed from , you normally see in the screen when sampling but I don't.Starting to wonder if Ive started on something i cant repair.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 15, 2023, 09:24:04 pm
content: There are too many, more random changes of parts and to little measurements / checks before. This way lots of parts get touched and possible new problems added.The part around U105 and U104 should not effect the normal voltage readings in the 10 V or 1 V ranges, even of the part is bad or possibly missing. So no need to worry about them for the start.These 2 may effect the 100 mV range and especially the 4 wire low value resistance ranges.Removing U103 (LM399) would leave more than 1 FET switch active at the same time for the gain setting. Worst case this may damage things, though chances are the parts would survive.For debugging the input amplifier it would help to start with the non AZ mode, though with a stable 0 V at the input it would not make a difference.For the 10 V range pins 1 and 2 of U103 should be at the negative rail, some -18 V.Pin 14 should follow TP100 = the amplifier output.TP101 as the buffered feedback signal is also of interest.The data for the 10 V calibration constant should come from the CAL ram chip.A 10 V signal is used in the ACAL procedure in the calibration of the HV divider. Where that signal is comming from is a good question. I don't know for sure, but it could come via the shunt chain and Ohms source.

author: IanJ
author_rank: Unknown
timestamp: May 15, 2023, 09:54:45 pm
content: Quote from: Ade911 on May 15, 2023, 08:26:04 pmDid you try extracting the Cal data via GPIB first?There are a few methods to do so.Theoretically, extract the ram data, (peace of mind achieved that you have it all backed up), then send to a programmer and burn the new Dallas ram IC's without disturbing the existing ones until you really have to.There are different variants of the Dallas ram IC's.PS. I use a Dataman S4 programmer.Ian.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 15, 2023, 10:11:01 pm
content: some search here may helpedhttps://www.eevblog.com/forum/repair/minor-repair-hp3458a/https://www.eevblog.com/forum/repair/hp3458a-sram-replacement-copy-or-calibrate/https://www.eevblog.com/forum/metrology/yes-another-3458a-repair-and-nvram-replacement-to-ramtron-fram/https://www.eevblog.com/forum/metrology/3458a-how-do-i-read-the-dallas-non-volatile-sram-date-codes/https://www.febo.com/pipermail/volt-nuts/2009-August/000052.htmlhttps://www.febo.com/pipermail/volt-nuts/2014-August/003482.htmlhttps://xdevs.com/fix/hp3458a_u4/https://xdevs.com/fix/hp3458a/#diag1repair of the slave test convergence ?? and some software down the pagehttps://xdevs.com/article/hp3458a_gpib/#calgpib

author: coromonadalix
author_rank: Super Contributor
timestamp: May 15, 2023, 10:42:25 pm
content: Annnnnnnnd this software piece to control the meter and do the nvram backupshttps://www.eevblog.com/forum/metrology/3458a-logging-via-windows-app-revisited/1st reply downhttps://www.eevblog.com/forum/metrology/3458a-logging-via-windows-app-revisited/?action=dlattach;attach=1782284

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 16, 2023, 06:15:37 am
content: @ ADE911:It's a pity that you did not use the search function of this forum upfront, and you listened to people who don't even own a 3458A.The TL866 plus would have been the better and maybe cheaper solution. It would have been necessary to download calram content via GPIB first.Now, after all these unthoughtful changes you made, it seems that calibration constants are probably lost.Frank

author: Ade911
author_rank: Regular Contributor
timestamp: May 16, 2023, 07:20:42 am
content: Thank you all for your advice and feedback, yes not proud of what i did but you sometimes get to a point where you do big changes usually around 2AM.I don't have a GPIB interface so hence the decision to very carefully remove the Dallas chips and copy. I've attached copies of the data uploaded from the chips, I believe its still ok unless I dropped a bit somewhere or you think otherwise.Re your advice and comments below, Ill carry these out today and report back.For debugging the input amplifier it would help to start with the non AZ mode, though with a stable 0 V at the input it would not make a difference.For the 10 V range pins 1 and 2 of U103 should be at the negative rail, some -18 V.Pin 14 should follow TP100 = the amplifier output.TP101 as the buffered feedback signal is also of interest.

author: Ade911
author_rank: Regular Contributor
timestamp: May 16, 2023, 03:44:44 pm
content: Quote from: Ade911 on May 16, 2023, 07:20:42 am

author: IanJ
author_rank: Unknown
timestamp: May 16, 2023, 05:18:17 pm
content: Quote from: Ade911 on May 16, 2023, 07:20:42 amYour U132 (Calram) is all FF.....so deffo didn't read properly.The other two U121(L) & U122(U) Settings RAM look like they might be ok.Ian.

author: Ade911
author_rank: Regular Contributor
timestamp: May 16, 2023, 07:32:08 pm
content: Ian thank you for checking , not sure what happened there , I checked all the fibre links , then it died before I swapped them out.I appreciate I need the system calibrating but can you get copies or does any one have a copy I cold down load to the device to see if this helps my unit at all or do i need to pay big bucks to get the unit fully calibrated againmoving on Dataman S4 programmer nice kit but i wouldn't use it enough to pay for itself , ill keep an eye out on eeee-bay.Any further feedback will be most welcome please

author: coromonadalix
author_rank: Super Contributor
timestamp: May 16, 2023, 09:26:44 pm
content: i hope you know how much this baby will cost to calibrate officially by Keysight ??You have a cadillac of meter, and the price will go with it, hoping you dont have any A3 board problems on u180 if i recall

author: alm
author_rank: Super Contributor
timestamp: May 16, 2023, 10:25:59 pm
content: Quote from: Ade911 on May 16, 2023, 07:32:08 pmUnless you have a friend who's a serious metrology geek, you will need to pay big bucks to get it adjusted and calibrated to factory specs. But the adjustment procedure is quite straight-forward if you don't care about accuracy (see the calibration manual), and since you have nothing to lose at this point in terms of accuracy, you might as well calibrate it to a very basic short, 10V from a bench supply and a stable(ish) 10k resistor. Just keep in mind that best possible end result is a meter with the accuracy of a 3.5 digit meter. You will want to first establish that the hardware is fully functional and stable before spending any money on having it adjusted.Please start being more methodical and read the huge amount of information that is out there before touching anything, because just losing the calram will have probably have set you back to the tune of $1k. Buying a GPIB interface would have been cheap compared to this.

author: Ade911
author_rank: Regular Contributor
timestamp: May 24, 2023, 07:37:11 pm
content: Todays statusIanJ very kindly checked my CAL file device but it only had H0 Data for some strange reason so alas thats gone. The only positive would be that the meter has not been calibrated since 2001 I believe or so the CAL label said, would someone else's CAL file assist in my recovery , if yes can any one share it please.Todays status - Still fails all calibration , HW, fails same issue as before.For some strange reason when you inject 10V and manually cycle through the X1, X10 , initially when you selected mv the meter wouldn't do anything now it states overload and samples , no idea why.Monitoring A1 TP100X1 10V I/P 10V TP100X10 10V I/P 1V TP100x100 10V I/P 0.1V TP100Below X1 [mV ?] 10V I/P Overload [ sampling] TP100 = 17.39VI thought the input to the A3 would never exceed 10V , is this incorrect.Ive also noticed that if you remove the 10V I/P and set to X1 TP100 starts to drive up towards 17.39V, is this normal.Also removed Jumper P100 and there is no input via P102 and still does it.Any idea where to check next please, I hope that because the voltage from A1 if above 10V the A-D will not sample and there is some limit circuit stopping 17V damaging the device.Trying to be logical and methodical in finding what is wrong.

author: IanJ
author_rank: Unknown
timestamp: May 24, 2023, 10:00:26 pm
content: Yep, Ade sent me his DS1220Y after I offered to double check it was indeed corrupted/data loss via my programmer......which, alas, it is.Ian.

author: Ade911
author_rank: Regular Contributor
timestamp: June 01, 2023, 07:43:41 pm
content: Hi 3458A knowledge group, so after ordering spare parts and fitting things still look bad. I really don't know what happened to the unit, be it a surge or something I really don't know;StatusRepositioned JMP600 to pin 1-2 [Right side] Front of meter facing me - Calibration security codeFitted NEW U105 --> LT1008CN8 out put was floating/driftingReplaced Q106 - Damaged CANReplaced Q107 with J112 [Found the resistance between the Gate and Drain on a meter changes over time] - Causing TP100 to rise in voltage to 17V or so.Replaced Q108 with J112 [ Not 100% sure before removing both which was causing the voltage on TP100 to rise.NowOriginal error still there.Input connected to +10V, +10V now read on TP100 [x10 = 1v , x100 = 0.1].Short input pins TP100 = 0VSet DC to mV [No short input floating] X1 or X 10 - DC TP100 now ready +17V !DC X1 ~ +1.5V , X10 +0.042, X100 +0.004VNot sure where the +17V is being generated from [High voltage relays not used I assume]If I try and do a CAL 0 the meter does something then beepsIf I try and do and CAL from the manual nothing changesIf I try AUTOCAL DCV nothing changesIm therefor not sure where to check next.Any advice would be so very much received please as I have no idea what to check next.New error messageSelect mVEnable TARMSystem now samples with overvoltage error - TP100 = +17VSelect X1 - TP100 = +10V , no sample [ ERRSTR 101,"CALIBRATION ERROR"

author: Ade911
author_rank: Regular Contributor
timestamp: June 11, 2023, 07:15:13 pm
content: Update after waiting for some parts to arrive, I was not aware how difficult and impossible to get some devices fitted it is.Same fault as from day one, now down to fault finding on the A3 bd. I confess my knowledge of the A3 bd is very limited so support will be very much appreciated. Again input gives 10v on the DC_AD pin of A3 unless you select mV which drives the voltage to ~17v.Not planned I touched U112  and its very hot and U111 and U140 are warm. Removed all three chips and bread boarded,U111  drawing 3mA so within spec even when the inputs are grounded [ output toggles].U112  +15V = 5mA , -15V = 3mA , again when the input is grounded the output toggled correctly.U140  drawing more than 10mA and output not toggling [+15V=5mA, -15V=3mA no connection. Pin 2 GND 2ma/ 2mA OP OC, Pin 3 GND 10mA/8mA OP OC]I was able to find in the UK a supply or RS LM6361 chips , I replaced both, tried again, same issue , U112 is still getting very hot. I need i guess to purchase a replacement although the chip seems to work fine on a bread board.From what I have read on line DC_AD is the main input voltage to A3. What does ZR_LO and ZR_HI do. ZR_HI reads 7.2V and ZR_LOW always reads 0V even when switched to Hz to activate the FET on A1.Voltages takenDC_AD = +10VU112 Pin2 = +1.539V Pin3 = -14.96VU110 Pin2 = +0.012V Pin3 = 0.00V Pin8 = +15.63VADC References are all correct so Im now thinking A3 has died , thoughts ?

author: Kleinstein
author_rank: Super Contributor
timestamp: June 11, 2023, 08:01:07 pm
content: It is normal that some of the OP-amps rund a bit hot. That is prie paid for high speed. With such a precision board it is not such a good idea to unsolder that many parts just based on a faint hint. Any step of soldering adds stress to the parts and other parts on the PCB and can add additional faults.So the advice is to do a little more measuring up front and thinking before soldering. The main suspects on the A3 board are U180, the obsolete Elantec comparators and maybe if lucky the fiber optic link.This does not mean to unsolder these, but more like check there supply and the comparator output signals. Have a look at TP112, TP140 and TP142.The ZR_hi / lo are the links to the reference. There is no switching so hopefully a very stable voltage on those signals.

author: Ade911
author_rank: Regular Contributor
timestamp: June 12, 2023, 04:04:25 pm
content: Hello Kleinstein, thank you for your feedback and advice. U140 was , is dead , doesn't do anything even on the breadboard so there was a problem with that one.VoltagesTP112 stable at -15vTP140 stable at -13.67vTP142 stable at 0.2vIf I select TARM the system samples in mV and DC_AD toggles between +10V and - 3 or so, is sampling controlled by the A/D or something else. After reading so many comments , convergence issues although the manual states the DC board can be generated by a dead A3 board is seems is this correct ?I did check the fibre links some weeks back and all seemed to toggle at some stage , no idea if the bit word was correct or not but still the 7414s changed state , should i check again how does this impact the reading of the voltage [Strange reading died when I was checking these devices maybe i turned the unit ON and OFF to many times in succession [10 second rule was applied].

author: py-bb
author_rank: Regular Contributor
timestamp: June 12, 2023, 05:01:43 pm
content: This is a standing offer for help as your last resort.I know a lot about the control/computery side of HP equipment spanning until the early 90s. Seriously. I've got a 5420A in the loft and a full set of manuals, I expect that to be similar. Indeed they share a lot (as the precursor to) with the control of the 62xx terminal stuff which is ALSO in a lot of stuff (like the HP protocol analysers from the mid 80s)IF you get nowhere I'm here and we can go through it but please last resort. I'd also like to know the sort of "blog post" story form of your issue if you solve it independently.I am not saying "I am HP Jesus" but I have spent a lot of time repairing this stuff. Standing by.

author: Ade911
author_rank: Regular Contributor
timestamp: June 14, 2023, 07:09:23 pm
content: Hello py-bb thank you very much for the kind offer of support.Sure i will share any information gathered but i really need guidance to confirm if U180 is dead or not.I dont know if there is any commands that will allow me to test U180, ive ordered a GPIB interface so the system can be interrogated maybe a little better than through the front keyboard. That should arrive early next week and then I need to read the user guide to test some basic commands.At present +10 V received at DC_AD. But no signal change U140 [see above values].TARM allows the system to sample and it registered overload in the mv range at 10V in put, if i drop the voltage to 1mv the system stops sampling and still shows overload.I understand U180 has an AC_AD maybe I need to check this to see if it samples AC voltage.Thats were I am, I need support from the people with the knowledge please.Many thanks

author: Kleinstein
author_rank: Super Contributor
timestamp: June 14, 2023, 07:26:47 pm
content: The much feared U180 failure usually starts with drift and if it get really bad causes an error message about convergance error. AFAIK this first happens for the slower conversions and I would expect the sampling to still work, just no valid result.The error described so far points more to other failures though one can not exclude that U180 is still bad.The lost CAL settings and configuration could be an issue to. Invalid content of the CAL ram and other settings could cause problems too.The need for the TARM part points in this direction.

author: Ade911
author_rank: Regular Contributor
timestamp: June 15, 2023, 07:28:37 pm
content: Hello Kleinstein, thank you for your support and feedback.General questions, is it possible to carry out a full calibration with empty dallas devices or does the calibration chip need a base line [copy from another system ]?is there any manuals that give a detailed overview of how the circuitry works, I understand the sections of the circuit but for example over voltage does this stop U180 running if the input voltage is to high.Whats the maximum voltage that should be applied to the I/P of U180 , in mV I get 17V I hope this has not caused a problem.Again support and advice is most welcome.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 15, 2023, 07:47:39 pm
content: The 15 V max from the amplifier stage should be OK, as an overflow in the mV range (and similar 1 V) is a more regular event and nothing to worry (e.g. happen also in ohm mode when open).The ADC should still run in some what than.For the calibration there is an extra CAL manual available. It should ideally work also with a corrupted CAL RAM content. A tricky point could be CAL steps for linearity corrections. Not sure if they are described too. The DC part should be relatively simple due to the ACAL system. The tricky part could be the AC part. A first point to check would be if the calibration is really the issue - it is unlikely to block further operation.A first point to check is a reset to default for the range and similar settings that a saved in the more normal SRAM part and retained over a power off.This should be in the normal manual.

author: Ade911
author_rank: Regular Contributor
timestamp: June 16, 2023, 10:45:08 am
content: Hello Kleinstein, thank you for your feedback.Ive looked and looked through google for an advanced cal manual but only found different versions shared by Tin, can you direct me please to where i can down load a copy.Im glad about the 17V , maybe the A/D livesIm also unsure about the default reset, I hunted for this to some time back but came to the conclusion this is carried out by the reset function on the front panel , is this correct [even with the existing error]

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 16, 2023, 12:04:33 pm
content: Hello Ade11,I disengaged myself here in this thread when you continued to randomly exchange components w/o previous systematic analysis / measurements.Again, in your situation, I would also not listen to people who don't own a 3458A themselves, and evidently only disorient you further.The 3458A requires a copper short, two references, 10V and 10kOhm, for the basic calibration.For high frequency VAC you need an HP3325A/B generator and thermocouples of 3V, 1V and 0.5V.Latter VAC calibration might not be needed if you don't use frequencies higher than 100kHz, or so.The 3458a will initialize a corrupted or blank cal RAM with the default values.These cal constants can be queried by CAL? 1,1 and CAL? 2,1: There's of course a dedicated calibration manual available, (03458-90017), better search at KEYSIGHT, they have the latest documents on their product page.There you will also find all updated service, operation and repair manuals, and about 18 Service Notes, one of them contains information about nvRAM replacements, which might not well fit here.I recommend to download the hp journal April 1989 which gives a lot of design background for the 3458A.The 3458A is one of the most linear DMMs in the world, therefore it is of courseno linearity calibrationof the A/D required.Being so sophisticated, it lacks any kind of power compensation of its 100:1 VDC divider, anyhow.I also urgently recommend that you update your EPROM firmware to 8 or 9, as your old instrument, from around 1995 probably still has the old 4 or 5 versions, containing a lot of flaws.Frank

author: Ade911
author_rank: Regular Contributor
timestamp: June 16, 2023, 01:50:46 pm
content: Hello Dr Frank,Hindsight is a wonderful thing but I do feel a bit of a donkey after rushing off in that manor. I didn't realise then how good these meters were as I was lucky to pay beer money for it when getting it some years ago. Now seeing how much care you take with these meters Ill certainly be more careful moving forward.Ill do what you recommend re the reading and documents thank you.Re the EPROM update, I have the single eprom, did I read that this needs to be purchased from keysight, or is there a procedure to reprogram in situ via the GPIB or programmer.Many thanks Ade.

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 16, 2023, 02:41:10 pm
content: Quote from: Ade911 on June 16, 2023, 01:50:46 pmNo, KS will only sell you a new, different controller board.And No, it's an EPROM, not an EEPROM.Simply purchase a blank EPROM (M27C4002-10 from STM, or eq. still available in some places*), a precision socket, download V9 from TiN's site and program it on your new programmer.See also here:https://www.eevblog.com/forum/metrology/repair-and-experiments-thread-hp-3458a-u2/msg1060699/#msg1060699Frank*Reichelt in Germany still listing this part for 8€75They also have these 62256-80 DIL28 SRAMs, 2€10, buy 4 EA for extending the memory.

author: Ade911
author_rank: Regular Contributor
timestamp: June 16, 2023, 02:48:03 pm
content: Hi Frank,Thanks for this advice, baby steps moving forward.Ill order the parts , refresh the software and then see what happens next.Updates to continue

author: Dr. Frank
author_rank: Super Contributor
timestamp: June 16, 2023, 03:05:54 pm
content: for completeness, here's a picture of my board with upgraded SRAM and updated nVRAMs.EPROM in this picture is still V8

author: Ade911
author_rank: Regular Contributor
timestamp: June 21, 2023, 07:24:06 pm
content: Hello Frank,So sorry for the delayed response, you will not believe it but out phone line was hit by lightning, yes really did blow up a powerline and router, sparks, exploded chips the works but the house didn't catch fire thank goodness.Anyhow, EPROM purchased from a company in the UK on E-Bay , they were new so I have a few spare, tried down loading ver 9 from TiNs website but the link is dead. Fortunately martinr33 had a copy that I managed to download which seems to work fine [thank you martinr33] - output_rev9.bin - CORRECTED 03FCB1D6.bin.REV now states 9.2 so I believe this is correct.I have also purchased a NI GPIB to USB convertor so can interrogate the unit via GPIB if required.I didn't add the extra memory yet just in case the unit is really dead so I want to get it going first.Error codes202 Hardware - Slave test convergence101 Calibration Required - SCALUpon power up I did also get the A/D can not read error but after trying a reset command it disappeared.Will now return to the A/D paper you recommended I read, slowly going through it but its hard going.Not sure if there is anything else I can check at present.Many thanks,Ade.

author: Ade911
author_rank: Regular Contributor
timestamp: July 02, 2023, 07:21:15 am
content: Hello Frank,Not sure if you can answer ; if i have access to another unit , would board swapping cause issues with the other unit, not ideal but run out of ideas before asking for a quote from the OEM.Im stuck, I don't seem to be able to find out anywhere where it states the system will still sample even if U180 is dead. It will sample if TRAM is activated , no input and DCV dropped to mV but im not sure why this happens but not in volt range.OVLD signal on U228 is working fine.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 02, 2023, 09:30:45 am
content: Board swaps allways come with some danger. At least swapping the digital boad should be relatively safe - with mainly the ESD and similar handling risk.One may even get away with just crossing the fiber optic links and still keep the boards in place.Before other swaps one should really make sure the supply is stable and safe - a bad supply would be a stupid mistake to damage a good board.

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 02, 2023, 09:23:29 pm
content: Quote from: Ade911 on May 07, 2023, 12:37:13 pmHello Ade,I'm trying to get some light in your recent descriptions..CR11 and CR 12 are on A1, SENTRY, Input Signal Conditioning, and on A4, inguard power supply (an "Inguard board" is not existent).That's very confusing.Please name all components correctly, best would be using the BOM designator, like A1CR11 and A1CR12, or A4CR11, A4CR12, and so on.Please describe in detail, which components were damaged at that time, A4CR11 + CR12 only?Frank (to be continued)

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 02, 2023, 09:32:25 pm
content: Quote from: Ade911 on May 05, 2023, 11:47:16 am@ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle.Therefore it's completely normal, that you see varying voltages on that pin.If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle.If you switch off AZ, then the 10V should be visible continuously @ TP11.Please try that out

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 02, 2023, 09:40:15 pm
content: Quote from: Ade911 on May 08, 2023, 01:18:11 pmWhat PCB / TP are you talking about?Where do you measure these signals?

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 02, 2023, 09:41:43 pm
content: Quote from: Ade911 on May 08, 2023, 07:45:28 amHow did you confirm / measure, that the EL2018 are working ok?Did you scope on their outputs?

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 02, 2023, 09:49:29 pm
content: Quote from: Ade911 on May 08, 2023, 04:57:50 pmHave you applied a fixed input voltage (only at the input jacks, of course!) for that test?Use TP100, instead of A1U100 - pin6. switch AZ off for that test.If you apply fixed 10V in 10V range, then you should see that 10V at TP100.apply 1V in 1V range, you should see 10V as well, repeat that for 100mV in 100mV range, pleaseQuote from: Ade911 on May 08, 2023, 04:57:50 pmPlease explain, what are you doing here, I do not know (or can't guess) what you mean with screen display, which sources you apply, and what mode / range you select in each case

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 02, 2023, 10:02:43 pm
content: Quote from: Ade911 on May 24, 2023, 07:37:11 pmTP100 (w/o AZ) is the input signal times the range amplification, i.e. x1, for 10V range, x10 for 1V range and x100 for the 100mV range.Where did you inject the 10V?At the input jacks only, hopefully.If you overload the amplifier, then of course you get +/-17V something out of U100.The input to the ADC can of course be +/-12V for full scale.

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 02, 2023, 10:06:12 pm
content: Quote from: Ade911 on June 01, 2023, 07:43:41 pmwhy have you changed A1Q107 / Q108?Put in the original transistors, please.Hopefully you now understand, how this circuit part works?

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 02, 2023, 10:39:46 pm
content: Quote from: Ade911 on July 02, 2023, 07:21:15 amYou have probably damaged A1 with all your component changes and measuring / injecting signals (I'm partly confused about your descriptions so far.).U180 rarely fails completely. That didn't seem to be the problem, initially.As the comparators A3U110, U11, U112, 140 are fully overloaded, is A1P100 set correctly?Have you touched the LTZ1000 reference board, and are its voltages and potential applied correctly, especially reference zero?Is the input amplifier with U100 / TP100 now working correctly, as described above?If you apply input signal of 10V in 10V range, w/o AZ,does that appear correctly @ DC_AD on A3 board?What are the voltages on A3U110, pin 2 +3?As long as you can't confirm that A1 is working properly, I would not swap any boards any more.In your situation, I would not jeopardize the other working boards by swapping, to write it in a polite manner.Frank

author: Ade911
author_rank: Regular Contributor
timestamp: July 03, 2023, 06:59:57 pm
content: Hello Kleinstein, yes its my sons so i dont think he would be very happy if something broke, I will not do any board swapping , just a thought before doing some thing drastic like sending to keysight.

author: Ade911
author_rank: Regular Contributor
timestamp: July 03, 2023, 07:07:59 pm
content: Quote from: Dr. Frank on July 02, 2023, 09:23:29 pmSorry for the confusion.A4 Inguard power supply - A4CR11 + A4CR12 were replaced as they were damaged [PCB is slightly damaged as well but repaired and working.

author: Ade911
author_rank: Regular Contributor
timestamp: July 03, 2023, 07:21:08 pm
content: Quote from: Dr. Frank on July 02, 2023, 09:32:25 pmwhen I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts.

author: Ade911
author_rank: Regular Contributor
timestamp: July 03, 2023, 07:36:28 pm
content: Quote from: Dr. Frank on July 02, 2023, 09:40:15 pmThis doesn't work now but when the meter would not sample, if i selected TARM i could at that time get a voltage at A1 TP100. it varied , this is why i looked at the circuit around A1 Q106, Q107 and Q108. Monitoring At TP100 without TARM enabled , the voltage would over 1-2 minuets rise to 10 Volts. After replacing A1 Q106 as it had a dent in the can ? , no change which was expected. I then removed A1 Q107 and A1 Q108, checking I found low resistance between S and G of Q107. As both devices were out the board I replaced with 112 devices which others had suggested. After powering back up the voltage drift disappeared, A1 TP100 is now stable.

author: Ade911
author_rank: Regular Contributor
timestamp: July 03, 2023, 07:53:17 pm
content: Quote from: Dr. Frank on July 02, 2023, 09:41:43 pmwhen the unit was reading some random voltage , yes I scoped the input and out put of EL2018 , as I also mentioned later on I removed and tested on bread board A3 U111, A3 U112 and A3 U140. All three devices did work but U140 exceeded the current drawn as stated on the manufacturers datasheet. I managed to purchase replacement devices for A3 U111 and U140 but need to use U112 as I cant purchase a replacement even though its still running very hot [greater than finger hot]

author: Ade911
author_rank: Regular Contributor
timestamp: July 03, 2023, 07:56:46 pm
content: Quote from: Dr. Frank on July 02, 2023, 09:49:29 pmSorry Frank, I dont recall , I believe I was checking all functions on the front panel and reading the main value on the front screen. Now nothing so I can not check sorry.

author: Ade911
author_rank: Regular Contributor
timestamp: July 03, 2023, 08:05:05 pm
content: Quote from: Dr. Frank on July 02, 2023, 10:02:43 pmI only inject via the front panel , never in circuit as I dont know it that well.At present I get what you have stated above , good to see +17 V is normal as well , I thought this may kill the A/D.Also no voltage drift since changing the FETs on A1 Q106,7,8

author: Ade911
author_rank: Regular Contributor
timestamp: July 03, 2023, 08:24:43 pm
content: Quote from: Dr. Frank on July 02, 2023, 10:39:46 pmPlease see my comments Ade > xxxxIs there a signal that shuts down the A/D if the voltage is to high or should the A3 board sample continuedly , its like something is blocking the A3 board reading voltage.Thanks Frank.

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 03, 2023, 10:37:08 pm
content: Quote from: Ade911 on July 03, 2023, 07:21:08 pmWhich NPLC length do you use?For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi.Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly.Under these conditions, that same signal should be visible @ TP100.If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message.Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1.Or try sampling with APER 1.Frank

author: Ade911
author_rank: Regular Contributor
timestamp: July 04, 2023, 07:01:09 pm
content: Quote from: Dr. Frank on July 03, 2023, 10:37:08 pmEvening Frank,The error messages I get at present when turning the unit on are202 Hardware failure - Slave test convergence110 Calibration Required - SCAL0 No ErrorI too think the system is frozen somehow, this is why I also checked A1 U10 Pin3 , this is sitting at +5V, I thought this may have caused measurements to stop but guess not.If I enable TARM [beeps as well]Inject +10VDC to the front of the unitScroll to mV I then get +0.VLD but the system is sampling on the front screen A1 TP10 still at +10VDCError message114 System Error - balanced rundown convergence0 No ErrorIf I enable TARM [beeps as well]Inject +1mVDC to the front of the unitScroll to mV I then get NO +0.VLD and the system is NOT sampling on the front screen A1 TP10 noise but no smooth voltage> 20mV [Noise could be from the power supply I am using ?]The unit only samples when the voltage is too high for the from screen, in auto nothing works.Is there another A->D that says the input is too high or ??

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 05, 2023, 08:49:18 pm
content: Quote from: Ade911 on July 04, 2023, 07:01:09 pmNo. There is an analog overload detection / clamp circuit on sheet 4 / 5 for protection of the fast input DCV path, A1R17/18.This is centered around A1U10, Q26/Q27 as low leakage diodes.This circuit has to switch off the input relays very fast to unload the DCV input.Have you already tried to use a very short NPLC number, like NPLC 0.01, 0.001, or so?There was a difference between the slow and fast sampling.All these rundown convergence error point towards A3, most probably the EL2018, maybe U180.But anyhow, as the input amplifier and the MUX might not work at all/incorrectly, maybe the control shift register chain is defect. Please check those on input / output DATA, like A1U105, sheet 3/5, and U6, U17, U9, U201, 203, U1, U4.. sorry, you have to search for the whole chain by yourself.. I don't know where this begins, and how it ends.I would trace from behind, maybe there is already a break in between..Frank

author: Ade911
author_rank: Regular Contributor
timestamp: July 06, 2023, 04:08:30 pm
content: Quote from: Dr. Frank on July 05, 2023, 08:49:18 pmHello Frank,No input, activating the Reset on the front panelAll inputs now checked, On all devices you listed pin 1 gives 2 10us pulses from 0V to 4V, Pin 2 shows data stream, Pin 3 I cant read the clock maybe too fast for my old scope so sits high [+5v] and pin 15 is high [+5v] , started to try and test outputs which is difficult to achieve.Maybe its not a problem, A1 U10C, Im checking data coming from A1 U17 to the DAC but I dont see a W/R signal. U10 Pin 9 is connected to all devices just checked - PIN 1, I see 2 10us pulses as before , Pin 10 is sitting at 2V , the output A1 U10 Pin 15 just sits high even when Pin 9 goes above the 2V threshold , is this normal , I though being a comparator it would flip and drive to 0V.Anyhow Ill carry on checking the other outputs where I can of the devices you mentioned.Many thanks

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 07, 2023, 10:34:34 pm
content: Quote from: Ade911 on July 06, 2023, 04:08:30 pmHi Ade,what kind of old scope do you have? Should be at least 20MHz BW, hopefully.The SR data might be clocked with 10MHz; I don't find the clock generator, or there should be a Hi speed UART on the analog side,which complements the UART A5U700, restoring clock and data, somehow. Well, that's the GA_Chip, A5U210, which serializes the data and creates all necessary signals for the different SR chains. It's clocked with 20MHz, so you should use a scope which has 60MHz Bw at least.This clock should be visible on all SR clock, and U10C serves as a simple inverter, delivering inverted clock for the DAC. Btw. there are ten SR '4094 in series on A1, in the following order: U1, U106, U307, U4, U14, U17, U6, U9, U201, U203. Check U203, pin 9, which isSERIAL OUT for the whole chain.If the clock signal is not present at all, and no data out at the last SR, then we might have found the problem.Frank

author: Ade911
author_rank: Regular Contributor
timestamp: July 08, 2023, 08:48:39 pm
content: Quote from: Dr. Frank on July 07, 2023, 10:34:34 pmHi Frank,Yes the clock is missing from U210 Pin 31, i traced and checked each signal back to the rear of U210 through R270,1,2 and the signal is missing [BTW you said A5 Bd but this should be the A3 bd i could only find U210 on A3, please confirm if I had another snr moment].All tests carried out on A3.Im still not sure if the clock signal runs freely or is it looking for a good state from U220. I ask as Im getting ripple on the supply on U220. The main incoming feed is smooth but on pin 40 / 20 I get 20mv ripple , even if I short out L222 & L223.The lines between U220 & U210 look fine , either +5V or 0V or 20mv Ripple.I think unless there is an interlock stopping the clock I can only assume U210 is dead.If you agree then Ill send out a request for a broken A3 Bd and see if I can exchange U220 which will be fun.Many thanks,Ade.

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 08, 2023, 09:05:29 pm
content: Quote from: Ade911 on July 08, 2023, 08:48:39 pmHi Ade,sure, should be on A3 board, sorry for that mistake.... you're really quick on the trigger to replace components.Please probe around that IC, if any other part is faulty, like U230, U131.. I can't hardly imagine, that such a part is gone. There's a 20MHz oscillator, search if you can find comprehensive signals around that.Please check pin 73, labeled IGCLK, if there's a clock available.

author: Ade911
author_rank: Regular Contributor
timestamp: July 09, 2023, 09:06:43 am
content: Quote from: Dr. Frank on July 08, 2023, 09:05:29 pmHello Frank,Sorry I should have shared more testing results.A3 BoardU230 20M oscillator OK, U131 OK , signal CK10 OK [ Not a square wave but still a clock pulse] .U211 , 212 change state during reset or changing front panel buttons, not sure if they have anything to do with how U210 functions.Unplugged P2 and P1 from the AC board to see if anything was affecting the signal DCCK_F [sitting at 5V]Where can I find the pin configuration of U210, I tried google but failed, guess Pin 11 U220 is acceptable - no clock , sitting at + 5V. U220 Pin 19 has a +5V clock pulse [more like a saw tooth]Good catch Frank, still learning from the master.Is this signal generated in U210 or U220 ?Tx Ade.

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 09, 2023, 09:32:07 am
content: Quote from: Ade911 on July 09, 2023, 09:06:43 amPin configuration of U210???It's on sheet 1 / 2of A3. What do you expect more?It's a hp programmed Gate Array, in my 3458A it's an ORBIT 6968A, don't know anything about this device.I have not measured inside my 3458A, but maybe the clock Pin 31 for the SR chain is only output, when needed. (*) Please scope on that pin, while you RESET the instrument, if there is an initial activity.What about pin 73, now? Is there a clock, or not?The 3458A currently does not work at all, anymore?Frank(*) That might be reasonable, so not to disturb the analog part by RF emission, during sampling.

author: Ade911
author_rank: Regular Contributor
timestamp: July 09, 2023, 12:09:23 pm
content: Quote from: Dr. Frank on July 09, 2023, 09:32:07 amHello Frank,I have the schematic , but when you said scope on pin 73 of U210 i was not sure where pin 73 is. I tried last night on paper to draw each pin and work out after Pin 1 where pin 2,3 and so on was but it made no sense so looked for the basic pins you mentioned connected to DCSTB_F, DCDA_F, DCCK_F.Pin 73 U210 - Pin 11 U220 , checking on Pin 11 U220 - power on goes high, goes low just before a failure of hardware Beep. Replicate by resetting the front panel , goes low just for a ms or so.Same error, as before;202 Hardware- slave test convergence110 Calibration Required - SCALNow checking to see why U220 voltage is not smooth on the chip pins but on the supply its smooth.

author: Ade911
author_rank: Regular Contributor
timestamp: July 17, 2023, 06:34:54 pm
content: Quote from: Ade911 on July 09, 2023, 12:09:23 pmHi Frank,I cant see anything else it can now be that the A3 board, I thought about trying to replace the 8051 but I dont know if the signal is generated in this device or U210. I did see some pulses but these could be a trigger issue on the scope as its not constant.Any other thoughtsMany thanks,

author: Ade911
author_rank: Regular Contributor
timestamp: August 01, 2023, 06:38:20 pm
content: Update sorry for the delay ...With Franks great support and advise we narrowed the problem down to the A3 board - U220 and U210. Unfortunately I have lost my clock pulse which drives all the shift registers from U210. You may see a pulse upon power up but then goes high.I also found that pin 20/40 U220 are not smooth, the supply has a ripple [see attached images].Question, anyone seen this issue before , I've never experienced this on a processor but maybe its normal and hence the two inductors in series with the supply lines which are smooooooth.I also wonder if this is at fault, can U220 be exchanged and does anyone have a copy of the internal software I could have please.Thoughts ?

author: CalibrationGuy
author_rank: Unknown
timestamp: May 19, 2024, 04:45:26 am
content: I know this thread is old, but I'm curious to know if you ever fixed this meter after all the input from the people on the forum, especially Dr. Frank.TomG.

author: Ade911
author_rank: Regular Contributor
timestamp: August 11, 2024, 07:46:49 am
content: Hello CalibrationGuy,Sorry for the delayed response, the 3458A was put to the back of the pile whilst I repaired two Datrons which are now calibrated and running well.The answer is no, in fact I powered it up yesterday to see what was happening but still no sample signal.Dr Frank is an amazing guy as well as some of the others who supported me , these people really know there stuff but I think I need a new A3 board :'(Tx ade...