02-28-2006, 08:38 PM
An open winding on RF transformer coils 1 and 10.
Primary to sec. shorts/leakage in these RF transformers.
Bad bandswitch contacts (or sneak shorts/leakage) for these coils; contacts F10, F11, D10, D11, C12, B10, B11, A1, A11.
Two RF transformers and switches are all that stand in the way from the antenna connector to the grid cap of the 6A8 in BC band position.
Try changing the 6A8 tube.
BC band OSC coil 17 is probably ok, since you get the upper half of the BC band. Check resistor 23, cap 22. Check for leakage/shorts in the OSC coil 17.
Don't suspect the RF tube since both SW bands are fine. If that 6K7 is working at SW freqs, then it should also work in MW as well.
Try changing the 6K7 tube. Clrean the RF tube socket contacts. Looks for bad/loose/rusty/corroded grounding rivets.
Primary to sec. shorts/leakage in these RF transformers.
Bad bandswitch contacts (or sneak shorts/leakage) for these coils; contacts F10, F11, D10, D11, C12, B10, B11, A1, A11.
Two RF transformers and switches are all that stand in the way from the antenna connector to the grid cap of the 6A8 in BC band position.
Try changing the 6A8 tube.
BC band OSC coil 17 is probably ok, since you get the upper half of the BC band. Check resistor 23, cap 22. Check for leakage/shorts in the OSC coil 17.
Don't suspect the RF tube since both SW bands are fine. If that 6K7 is working at SW freqs, then it should also work in MW as well.
Try changing the 6K7 tube. Clrean the RF tube socket contacts. Looks for bad/loose/rusty/corroded grounding rivets.
Chuck Schwark,
The Philco Repair Bench
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