"Tony" wrote in
:

Hello, and thank you for reading my post.

I've recently acquired a used Tek 2235 at a local auction.
Cosmetically, the unit looked brand new like it was hardly ever used.
The reason why may be that there is a slight problem with the unit,
possibly somewhere in the power supply section. When power is applied,
the unit exhibits something similar to the 12kHz "chirp" symptom, in
that once every second or two, the power LEDs flicker and an audible
chirp noise can be heard coming from the transformer.

I've tried some basic troubleshooting steps as follows:

- Visually inspected the circuit boards for obvious component failures
- Tested all diodes and capacitors of the power supply out-of-circuit
to make sure they were still OK

did you check the PS filter caps for good ESR? Switchers (and 2200 series
scopes)are prone to bad electrolytics WRT ESR. Don't forget the electolytic
cap for the housekeeping supply for the TL594 IC. (100uf,IIRC)

(I don't have 2235 schematics or manual,so I can't go into specific part
numbers,my memory just isn't that good.;-) )

You could have a problem with a HV cap breaking down,perhaps in the -2KV
cathode supply.


--
Jim Yanik
jyanik
at
kua.net