Tektronix 555 problem


The upper beam on this scope will only sweep unless set to trigger from the lower beam time base. I can only get a dot with the upper beam set to the (A) upper time base. Both time bases are set the same for recurrent. I have tested all the upper time base tubes and all good. The supply voltages checked as per the Tek schem. for the time base seem to be fine. There is a "sawtooth out" jack on the front of the upper time base and from what I'm seeing using the working trace, there is no sawtooth waveform there. I only have this scope to check that with. Before I dig into it further, thought I'd ask you fellows here if you've had any experience with this. Been many years since I've worked electronic problems. I do have a time base extender. Thank for any time and advice.


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