Today's Mystery Guest (RCA CTC-4)

[old_coot88]

Originally Posted by Phil Nelson

Okay, with that lash-up, I see a regular waveform at L42 (pin 3 of the oscillator). This is with no signal to the receiver and a high sweep rate.

Yowie zowie! What's the actual p-p amplitude of that?
Looks like the thing is actually running.
OK (assumimg you haven't unmounted the old CW xfmr yet), just take the new one and connect its primary in place of the old one, using a couple of short leads (after removing that jumper). See if the osc still runs.

[Phil Nelson]

Maybe this photo will give a better idea what I'm seeing. My scope has a lot of trouble locking onto the signal -- hope it's not a phantom.



Edit: I just connected the primary of the new transformer in place of the old one (i.e., B connected to pin 1 and E connected to junction of R250/CC211. I get the same waveform, whose amplitude collapses if I temporarily disconnect the primary.

Phil Nelson

[old_coot88]

Originally Posted by Phil Nelson

...I just connected the primary of the new transformer in place of the old one (i.e., B connected to pin 1 and E connected to junction of R250/CC211. I get the same waveform, whose amplitude collapses if I temporarily disconnect the primary.

OK. Now reconnect the old CW xfmr's primary. Does it kill the osc? If so, this proves the old xfmr is at fault.
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But the question remains, with the new xfmr's differences, will it deliver correct phasing, amplitude etc downstream?
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Also, is the osc running with the new L42 or the old one?