02-25-2014, 09:01 PM
Warren;
You do not say what you may have already tried in the effort to solve the problem.
The 47-1230 model uses an approach similar to that of many other manufacturers after the war when the FM band was moved to 88-108mHz. The IF coils for the FM IF circuit are in series with the coils used for AM. The AM coils act like a signal ground for 10.7mHz IF frequencies so that when in the FM mode they do not actually do anything but pass the DC voltages to grids and plates of the various IF tubes. However when switched to the AM mode, the AM coils of the IF circuitry begin to handle the 455kHz signals for the AM circuitry. It is possible that there is a problem with one or more of the capacitors across a primary or secondary of one of the AM IF transformers. It could be due to the silver mica disease, although it is more common with sets manufactured in the 1950s it could still be an issue for your set.
One thing I would suggest first would be to use some Deoxit to clean the tube sockets and the push button switches and any switches that are involved with the AM/SW/FM band switching to see if cleaning will improve things. Sometimes just removing and re-insergint tubes into their sockets will clean both socket and pins enough to restore function if corrosion is the issue. Also just wiggling tubes in their socket can sometimes pinpoint a trouble area.
Let us know what you have tried and what results or lack of results you have and we can go from there.
Joe
You do not say what you may have already tried in the effort to solve the problem.
The 47-1230 model uses an approach similar to that of many other manufacturers after the war when the FM band was moved to 88-108mHz. The IF coils for the FM IF circuit are in series with the coils used for AM. The AM coils act like a signal ground for 10.7mHz IF frequencies so that when in the FM mode they do not actually do anything but pass the DC voltages to grids and plates of the various IF tubes. However when switched to the AM mode, the AM coils of the IF circuitry begin to handle the 455kHz signals for the AM circuitry. It is possible that there is a problem with one or more of the capacitors across a primary or secondary of one of the AM IF transformers. It could be due to the silver mica disease, although it is more common with sets manufactured in the 1950s it could still be an issue for your set.
One thing I would suggest first would be to use some Deoxit to clean the tube sockets and the push button switches and any switches that are involved with the AM/SW/FM band switching to see if cleaning will improve things. Sometimes just removing and re-insergint tubes into their sockets will clean both socket and pins enough to restore function if corrosion is the issue. Also just wiggling tubes in their socket can sometimes pinpoint a trouble area.
Let us know what you have tried and what results or lack of results you have and we can go from there.
Joe
