Keithley 2002 DMM repair

[TiN]

Plesa on fire. What errors you have left ?

[plesa]

Not yet, but strange is that meter works like charm.
But in self test these errors remains, probably it needs calibration DAC only.

400   Calibration/Frequency Compensation DAC
400.1   -4.36V DAC Output
400.2   -2.15V DAC Output
400.3   0V DAC Output
400.4   +2.33V DAC Output
400.5   +4.48V DAC Output

401 Series  Regulator
401.1   Regulator

402 Series  Switching
402.1 Frequency Switch

405 Series   Absolute Value (X10 Gain):
405.1    Gain Comparison (Large +DAC Output)
405.2    Gain Comparison (Non-inverting)
405.3    Gain Comparison (Small +DAC Output)
405.4    Gain Comparison (Non-inverting)
405.5    Gain Comparison (Small -DAC Output)
405.6    Gain Comparison (Inverting)
405.7    Gain Comparison (Large -DAC Output)
405.8    Gain Comparison (Inverting)

406 Series   Sample and Hold Circuit:
406.6   Sample and Hold Voltage Comparisons

[plesa]

Checked signal path and DAC output is OK, including 1458 OpAmp ( slightly off). In this part of troubleshooting steps in self test are quite handy.
Following components needs to be inspected U419/DG444, U414/DG408, and U403/LT1097.
Unfortunately I do not have more analog switches (DG408/DG444)  needs to order another batch of components.

[plesa]

Today repair has been finished, the 400 series error has root cause in the U414 where I forgot to solder pin 7
AD637J has been replaced with AD637B anyway.

Based on this repair I pretty confident that next repair will be piece of cake. But unfortunately there are only few 2002 meters on eBay.
For repair it seems to be better alternative than 3458A.