HP 3458A ; A/D board spare part availibilty and cost

[aronake]

Here are my statistics on my 5 3458a

Production year   A3 swap time   Calnum   Comments
2006                  2011               92          Extremely stable, opt 002
1991                  1999               1243      Extremely stable, used to serve in a cal lab
1999                  Not swapped    19         Extremely stable, used to serve in a cal lab, very good TC
1998                  Not swapped    1           Just passes SN18 test, but at 0.4 ppm/day not good enough. Also a bit high TC.
2000                  Not swapped    8           Suffers very high TC, around 1 ppm/C, so drift kind of masked by TC, but fair to assume its drifty.

The 1998 and 2000 meters have statistical bias, being drifty at purchase (which I was aware of).

Obviously not very strong statistics with 3 samples, but that means 67% of the stable meters have had the A3 replaced. And the drifty A3 span from 1991 to 2006 here. And seems there are much newer meters that developed (or had from production) drifty A3.

1998 meter looked terrible when i got it. It has serial 2823A20500, so closest brother to one of Tins repair projects https://xdevs.com/fix/hp3458_u4/. So maybe the "angry hulk" bought two meters to abuse in parallel.... It looks nice now after some refurbishment, but has some A3 drift. Over half a year it has come down from 0.6 ppm/day to just under 0.4 ppm/day. so maybe if it is allowed to run for another year or so it may get acceptable.

[srb1954]

Here are my statistics on my 5 3458a

Production year   A3 swap time   Calnum   Comments
2006                  2011               92          Extremely stable, opt 002
1991                  1999               1243      Extremely stable, used to serve in a cal lab
1999                  Not swapped    19         Extremely stable, used to serve in a cal lab, very good TC
1998                  Not swapped    1           Just passes SN18 test, but at 0.4 ppm/day not good enough. Also a bit high TC.
2000                  Not swapped    8           Suffers very high TC, around 1 ppm/C, so drift kind of masked by TC, but fair to assume its drifty.

The 1998 and 2000 meters have statistical bias, being drifty at purchase (which I was aware of).

Obviously not very strong statistics with 3 samples, but that means 67% of the stable meters have had the A3 replaced. And the drifty A3 span from 1991 to 2006 here. And seems there are much newer meters that developed (or had from production) drifty A3.

I can only add one data point to your statistics:
Production year   A3 swap time   Calnum   Comments
2005                   2022              56           Had severe drift prior to replacement of A3 at 1.6ppm/day per the SN18 test. After replacement of A3 drift dropped to 0.003ppm/day but temperature coefficient is a little on the high side at 0.43ppm/℃

Did you check the serial numbers of each of your units on the Keysight service support site for recommended updates? There are probably a number of updates/fixes that apply to your earlier units.

[aronake]

I felt like being a bit experimental. So had the U180 swapped between the A3 that have a bit of excess TC with the one that have a bit of, but still in spec drift. The U180 is pretty easy to desolder if using a good desolder gun. Just had everything packed together and started some new test runs.

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