06-09-2012, 07:26 AM
I think one or more of the mica caps across each tuned section of the Mystery Control RF transformers may be bad.
As you know, the RF transformers in the Mystery Control section of the receiver are slug tuned. Each tuned circuit has a fixed mica cap across it.
These mica caps were only sealed in wax, making them prime targets for corrosion.
If these mica caps go bad, you won't be able to tune the RF transformer properly.
When I had my 41-616 apart, I replaced the mica cap in the first RF transformer mainly "just because." It seems to work with the new dipped 50 pF mica I put in place of the old one, although as I recall, I think the value of the original may have been closer to 70 pF? At any rate, I had no trouble aligning the Mystery Control circuitry to its original 395 kc frequency (it is stamped with a big 9 on the stepper unit box, meaning Code 9 or 395 kc).
Be aware that the micas in the RF cans of the 39-55 chassis you're getting from me may also be bad.
As you know, the RF transformers in the Mystery Control section of the receiver are slug tuned. Each tuned circuit has a fixed mica cap across it.
These mica caps were only sealed in wax, making them prime targets for corrosion.
If these mica caps go bad, you won't be able to tune the RF transformer properly.
When I had my 41-616 apart, I replaced the mica cap in the first RF transformer mainly "just because." It seems to work with the new dipped 50 pF mica I put in place of the old one, although as I recall, I think the value of the original may have been closer to 70 pF? At any rate, I had no trouble aligning the Mystery Control circuitry to its original 395 kc frequency (it is stamped with a big 9 on the stepper unit box, meaning Code 9 or 395 kc).
Be aware that the micas in the RF cans of the 39-55 chassis you're getting from me may also be bad.
--
Ron Ramirez
Ferdinand IN
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