[volt-nuts] Fluke 335A

[J. L. Trantham]

Spent some time with my 335A this weekend and found 4 dead aluminium electrolytic capacitors, 3 of which were 50 uF 50 V and one was 25 uF 50 V.  They were C3, C8 and C11 (advertised as 20 uF 50 V on the schematic, parts list and the picture in the manual but was really 25 uF) on the A5A5 Auxiliary Power Supply and C7 on the A8 High Voltage Motherboard P/C Assembly.  I replaced them all with 47 uF 50 V aluminum electrolytics that measured slightly more than 50 uF on the meter.  the 5 mV, 60 Hz 'ripple' on the output is now gone.

Also found some shorted 'wires' on the 1 uV digit rotary switch.  Separated those and inspected the rest of the switches.

Now, it is able to be aligned right down to zero.  I have not had time to adjust the 'decade' resistors but I am pleased that it is fairly stable at the 1 uV level and I am able to display 123.456 mV (+/- 1 uV) on my 3478A simply by dialing up 0.123456 V on the 10 V scale.  Perhaps not the 'ultimate' but not bad.  I think I should be able to use it as a 'standard' to align my old 8050A's.

Joe