My CTC-16XL Project.

[old_tv_nut]

suggestions:

Since the ceramic disc caps are unlikely to be failures, do some more troubleshooting before all the effort of replacing everything.

Make sure you cannot go through zero beat by adjusting A31/L16 with point J grounded. If you can get zero beat, there is no problem with the oscillator.

If you can get zero beat with J grounded, unground it and observe what happens. If the oscillator frequency changes only slightly, then look at point J with your scope and a voltmeter to see if the beat frequency appears coming out of the phase detector, with an average value about zero. If you now tune A31/L16, you should see the beat frequency change on the scope. If you get very close to zero beat, the DC voltmeter will start to follow the slow voltage swings of the detector output. If you see the detector output behaving normally , the phase detector is OK, otherwise it is suspect. So, if the detector output is OK and the oscillator is OK, and you still have no lock, that points to the control (reactance tube) circuit.

[Yamamaya42]

Originally Posted by old_tv_nut

suggestions:

Since the ceramic disc caps are unlikely to be failures, do some more troubleshooting before all the effort of replacing everything.

Make sure you cannot go through zero beat by adjusting A31/L16 with point J grounded. If you can get zero beat, there is no problem with the oscillator.

If you can get zero beat with J grounded, unground it and observe what happens. If the oscillator frequency changes only slightly, then look at point J with your scope and a voltmeter to see if the beat frequency appears coming out of the phase detector, with an average value about zero. If you now tune A31/L16, you should see the beat frequency change on the scope. If you get very close to zero beat, the DC voltmeter will start to follow the slow voltage swings of the detector output. If you see the detector output behaving normally , the phase detector is OK, otherwise it is suspect. So, if the detector output is OK and the oscillator is OK, and you still have no lock, that points to the control (reactance tube) circuit.

I now have the caps I ordered, not had a chance to go over things to check / replace things yet, spent most last week resting, will try this weekend, I understand MOST of what you said to check, but the term “zero beat” is new to me, and I really am not sure how to apply it to the situation at hand. T_T
(looking it up did not help much )
PLZ forgive if it seems silly to ask, but, I grew up mostly in the digital/ solid state age, tubes were already way out when I was in the Electronics class in HS, “zero beat” may have been covered, perhaps, I may have just forgotten :/