Re: tek 2215 trace position issues


Roger Evans
 

I know you said earlier that Q386 and Q387 tested OK but the measurements you have made around Q360 do point to one or other of Q386/Q387 being the culprit. It is not easy to make definitive measurements in circuit with all the relatively low value resistors around Q386/Q387.

If you centre the vertical position pot you should get the bases of Q350 and Q360 both close to 0V, this doesn't need to be precise. Then measure the following voltages wrt ground:

Q377 collector Q387 collector
Q377 emitter Q387 emitter
Q376 collector Q386 collector (these should be the same as the line above but if you can make a second measurement it confirms no faults on the PCB)
Q376 emitter Q386 emitter (these should be the same but check as above)

If it is not obvious which transistor has failed open circuit then additionally measure the voltages on the bases of Q386 and Q387 (and Q376 and Q377 if you want to be thorough).

This doesn't distinguish between Q386 having an open collector-base junction and Q387 having an open emitter-base junction, at this point you probably need to remove at least one device.

Apologies to Ozan for repeating a large fraction of what he said earlier!

Regards,

Roger

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