05-26-2016, 10:38 AM
Thanks, Terry.
Well, I used my crude CIE sine wave generator which did give me audible signals when probing the grids of the power tubes, the phase splitter and the audio amp triode.
The radio failed the very first test for the FM circuit, though: no signal when probing the grid of the 7R7 tube (pin 6).
I retested the tube, which is strong on the pentode and good but not particularly strong on the two diodes. It was a new-in-box National Union.
The other possible causes revealed nothing, although my meter won't test the 100pF cap (C323) and I am out of that value so I'll need to order some and replace it. The C325 is new and is oriented correctly. Z302 does ohm out correctly per the SM with no opens. C324 is a new .01uF (not a .008uF) and is connected right. C205 is another 100pF cap on the volume control and I could not test that. R318 has drifted a little high to 118K Ohms but is not open. R319, the 6.8M, I could not test that high.
The last possible cause: 'Z302 misaligned' has me a little nervous and I don't want to make things worse, so I will leave that alone for now, get a couple 100pFs in there, put fresh 100K and 6.8M resistors, and also test the 7X7 which last night I didn'y remember to test. It was a new-in-box Tung Sol.
Does my reasoning sound good so far or is there anything else that comes to mind?
Well, I used my crude CIE sine wave generator which did give me audible signals when probing the grids of the power tubes, the phase splitter and the audio amp triode.
The radio failed the very first test for the FM circuit, though: no signal when probing the grid of the 7R7 tube (pin 6).
I retested the tube, which is strong on the pentode and good but not particularly strong on the two diodes. It was a new-in-box National Union.
The other possible causes revealed nothing, although my meter won't test the 100pF cap (C323) and I am out of that value so I'll need to order some and replace it. The C325 is new and is oriented correctly. Z302 does ohm out correctly per the SM with no opens. C324 is a new .01uF (not a .008uF) and is connected right. C205 is another 100pF cap on the volume control and I could not test that. R318 has drifted a little high to 118K Ohms but is not open. R319, the 6.8M, I could not test that high.
The last possible cause: 'Z302 misaligned' has me a little nervous and I don't want to make things worse, so I will leave that alone for now, get a couple 100pFs in there, put fresh 100K and 6.8M resistors, and also test the 7X7 which last night I didn'y remember to test. It was a new-in-box Tung Sol.
Does my reasoning sound good so far or is there anything else that comes to mind?
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