Re: Tek 465: CH1 No signal, CH2 signal reads a fraction of input, V Pos distorts signal


Greenpitu@...
 

Hello Roger,

Thanks for your email. I think I have good news!

I opened up the scope once again to proceed as indicated and measured 174.8 ohm on one side of R429 (i.e. R427) and about 1 ohm on the other (R428). Confused as I was I went back to the service manual pictures and I realized my mistake: when I then tried to adjust R429 the other day to move the trace line at the center of the graticule I was operating and adjacent pot instead... no wonder the trace wasn't moving! :-)

It took a few rounds of calibration on the Vertical output amplifier bias, the vertical output centering, Ch1/Ch2 step attenuator balances and Ch1/Ch2 position centering adjustments to get a stable, centered trace that wouldn't compress/expand when operating Ch1/Ch2 vertical position. I will repeat the operation and further checks once I get hold of second scope and trustworthy generator.

At this stage I'd say the issues originally posted on this topic are fixed on both Ch1 and Ch2. I have the occasional arcing (almost absent now after thorough cleaning in the area and with scope cover on) and just sourced the neutral silicon as per instructions above.

I am immensely grateful to Roger, Raymond, Simon, Chuck, David and scm for all your guidance and patience to help fix this great scope!

Best regards

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