Re: Tektronix 2246 flickering screen, ch2 not working.


grusus@...
 

Schematic is on page 298 of service manual.
https://www.tek.com/manual/2246-service-manual
Look there:
Trace (I input 1kHz square) is ok at input of AT127. At input of U122 there is very distorted triangle(looks like triangle), also on output. (on ch1 there is nice square at those points).
I don't see there any extra FET's. Must check C124 if it is not pulling down if case it is wrong.

I am going to change all electrolytics. There is one on logic board and many more on mainboard. I just don't want to remove mainboard many times beacuse it's very long procedure.
Flickering also is on traces itself. Not only on redouts. Alse there are gaps/cuts/ripple in traces. Turning ccw redouts helps a little but not much.
Also i noticed today that when i switch to B traces are visible only from left to center of the screen. Moving lef/right moves traces but they only take half of the screen. On A there is no problem.
Pots and cons cleaned.

Many thanks for tips.
If you have experience in scope repairs and have some free time, please check schematics in service manual. I will be very gratefull. :-)

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