Electronics > Repair
HP 3458A - Fails Slave Test - Convergence
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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:

--- Quote from: Ade911 on June 16, 2023, 01:50:46 pm ---
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.

--- End quote ---

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.
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