fluke 3330B fault current output

[NRP_SANTOS]

Hello friends, I'm looking for help repairing my fluke 3330b.
his problem is in currents above 3ma. Whichever scale is selected, it always maintains 6ma of output.
Best regards
nrp_santos

[alm]

Is it working below 3 mA? Does it jump right to 6 mA as soon as you set the current above 3 mA?

I haven't studied the schematic, but sounds like it might be a bad transistor to me. Although I would also check all voltage rails for ripple (bad caps).

Be aware there are lethal voltages inside, so be very careful operating it with the covers off.

[NRP_SANTOS]

hello Alm,
I appreciate your availability.
It works below 3ma.
above the 3ma range it always maintains the 6ma output value.
best regards,
nrp_santos

[Dr. Frank]

Hello,
does this error occur only in constant current mode, or also in constant voltage mode?
Frank

[NRP_SANTOS]

Hello Frank,
The problem only occurs in current.
When I select above 3ma.
the signal measured oscilloscope the input and output of the PCBs (A4A2 chopper amp., A4A3 differecial amp., and A4A4 series pass drive) occurs a 100hz oscillation.
NRP_SANTOS