Exterior

Testing

Connected to AC source configured for 120 VAC 60 Hz output we can observe that 34401A on power on eats about 10.5 W. This is about right for good working meter.

It beeped once on boot and came right up, showing some readings even without repairs :)

Connecting 10 V and other DC voltages from nearby Keithley 2400 SMU revealed no issues.

Meter also passed internal quick self-test procedure with a happy “PASS”.

Firmware version is 10-05-02.

Transparent board images

Overall stitched panoramic image (middle section didn’t fit):

Close-up details following ADC section

Digital CPU section

Rear terminals and earth-referenced logic

Current range shunt, relays and F/R shadow switch

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