Electronics > Repair

Tek 577 Step amplifier problem

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Found the culprit of the -30V problem.
I bent one of the K436 contacts while cleaning as suggested here, in a way that a NO contact was NC.
I will proceed to troubleshoot the staircase generator.

I fixed the relay contacts, and no more problems with the +30V/-30V supplies.
Now there is a nice staircase signal at TP360 that change direction as expected when the polarity switch is pressed.
I am testing the unit in Voltage Steps mode.
The cam switch contacts for the low range voltages are not working as expected, but I will address this problem later.
I can get a good "clean" signal from .5V up at pin 2 of U380A, but NO SIGNAL at all at the output, pin 1.
I have tried to disconnect VR380/VR382 and Q384/386 and also replaced U380 without success.
Any help will be greatly welcome.


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