08-22-2015, 10:05 PM
Yes, if the previous owner replaced the cap with a poor quality ceramic, it could certainly cause the drift with temperature.
It should be a mica or a NPO ceramic if original. Ceramic caps were just coming into general use in the late 1940's so it is possible that a ceramic might have been installed originally. If it was ceramic it would be tubular or "dogbone" style, not the usual disc ceramic caps you see today.
Low grade ceramic caps have a huge temperature coefficient, so it will be obvious when you hit it with freeze spray or heat with a hair dryer.
What freq are you tuned to when you notice the drift? The effect will be much greater at the high end of the band than at the lower freqs.
It should be a mica or a NPO ceramic if original. Ceramic caps were just coming into general use in the late 1940's so it is possible that a ceramic might have been installed originally. If it was ceramic it would be tubular or "dogbone" style, not the usual disc ceramic caps you see today.
Low grade ceramic caps have a huge temperature coefficient, so it will be obvious when you hit it with freeze spray or heat with a hair dryer.
What freq are you tuned to when you notice the drift? The effect will be much greater at the high end of the band than at the lower freqs.
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