HP 3458A - Fails Slave Test - Convergence

[Ade911]

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 - shorted together all 4 inputs and selected azero off
For the 10 V range pins 1 and 2 of U103 should be at the negative rail, some -18 V. - correct
Pin 14 should follow TP100 = the amplifier output. - Pin 14 and TP100 are sitting at 0 volts
TP101 as the buffered feedback signal is also of interest. - sitting around 0 volts

[IanJ]

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.

Your 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.

[Ade911]

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 again 

moving 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

[coromonadalix]

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

[alm]

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 again 

Unless 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.

[Ade911]

Todays status

IanJ 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 TP100

X1 10V I/P 10V TP100
X10 10V I/P 1V TP100
x100 10V I/P 0.1V TP100

Below X1 [mV ?] 10V I/P Overload [ sampling] TP100 = 17.39V

I 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.

[IanJ]

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.

[Ade911]

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;

Status

Repositioned JMP600 to pin 1-2 [Right side] Front of meter facing me - Calibration security code

Fitted NEW U105 --> LT1008CN8 out put was floating/drifting

Replaced Q106 - Damaged CAN
Replaced 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.

Now

Original error still there.
Input connected to +10V, +10V now read on TP100 [x10 = 1v , x100 = 0.1].
Short input pins TP100 = 0V

Set DC to mV [No short input floating] X1 or X 10 - DC TP100 now ready +17V !

DC X1 ~ +1.5V , X10 +0.042, X100 +0.004V

Not 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 beeps

If I try and do and CAL from the manual nothing changes

If I try AUTOCAL DCV nothing changes

Im 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 message

Select mV
Enable TARM
System now samples with overvoltage error - TP100 = +17V
Select X1 - TP100 = +10V , no sample [ ERRSTR 101,"CALIBRATION ERROR"

[Ade911]

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 [AD848] and its very hot and U111 and U140 are warm. Removed all three chips and bread boarded,

U111 [LM6361] drawing 3mA so within spec even when the inputs are grounded [ output toggles].

U112 [AD848] +15V = 5mA , -15V = 3mA , again when the input is grounded the output toggled correctly.

U140 [LM6361] 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 taken
DC_AD = +10V
U112 Pin2 = +1.539V Pin3 = -14.96V
U110 Pin2 = +0.012V Pin3 = 0.00V Pin8 = +15.63V

ADC References are all correct so Im now thinking A3 has died , thoughts ?

[Kleinstein]

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.

[Ade911]

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.

Voltages
TP112 stable at -15v
TP140 stable at -13.67v
TP142 stable at 0.2v

If 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].

[py-bb]

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.

[Ade911]

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

[Kleinstein]

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.

[Ade911]

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.

[Kleinstein]

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.

[Ade911]

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 lives 

Im 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]

[Dr. Frank]

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 course no linearity calibration of 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

[Ade911]

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.

[Dr. Frank]

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.

No, 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/#msg1060699

Frank

*Reichelt in Germany still listing this part for 8€75
They also have these 62256-80 DIL28 SRAMs, 2€10, buy 4 EA for extending the memory.

[Ade911]

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 

[Dr. Frank]

for completeness, here's a picture of my board with upgraded SRAM and updated nVRAMs.
EPROM in this picture is still V8

[Ade911]

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 codes
202 Hardware - Slave test convergence
101 Calibration Required - SCAL


Upon 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.

[Ade911]

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.

[Kleinstein]

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.