Re: How to troubleshoot a faulty 7B92A?


Thierry Delaitre
 

Thanks Mark

an update

I have cleaned the time/div contacts.

I also verified S800 and S490 offline as well as using the scope.

AR only works when the time div knob is pulled.

When the time div knob is pushed
- AP remains low and BM remains high
- J & K of the 1st flip/flop are high and the flip/flop is meant to operate in toggle mode according to the 74LS112 data sheet
- the clock continues to operate at the input of the flip/flop
- is it expected that AP remains low and BM remains high ?

There is a nice sweep at TP450 and no sweep at TP550

I verified all transistors for the DLY'D sweep gen (5)

There does not appear to be a signal at AD (voltage is 0.2V).

I therefore checked TP355 on the delayed triggered board (3) and can see a signal at TP355.

Should I be searching why there is no signal at AD which may explain why there is no sweep at TP550?

Thanks

Thierry

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