I am in the midst of repairing a 34970A with multiple issues.
The unit started with selftest errors as below:
604 Self-test: A/D slope convergence
609 Self-test: DC gain x1
610 Self-test: DC gain x10
611 Self-test: DC gain x100
612 Self-test: Ohms 500 nA source
613 Self-test: Ohms 5 uA source
614 Self-test: DC 300V zero
615 Self-test: Ohms 10 uA source
616 Self-test: DC current sense
617 Self-test: Ohms 100 uA source
619 Self-test: Ohms 1 mA source
621 Self-test: AC rms full scale
Replacing all
AD711 AD706 took away all the error, though the actual culprit was one
AD711 AD706 (U400), might as well change all I suppose.
Upon changing self-test passed. Measurements were super out of tolerance. Zero adjustment did not go thru stating no signal, That directly pointed me to possibility of defect on the input relays.Had to wait an extra week after the relay that Element14 delivered came broken in half.
.
Replacing relays, Zero Adjustment passed. Yet I am noticing in all functionality measurements are slowly drifting up, another weird error i have encountered is if I am to perform -10V adjustment, the meter gives me error 731 Cal: A/D turnover correction out of range, in all positive ranges adjustment is going thru.
Next up will be measuring the supply voltages to see if they are stable or not, maybe its drifting causing this issue.
Any other idea is much appreciated.