11-12-2006, 08:19 AM
Sounds like an oscillating IF circuit.
Did you replace the paper and electrolytic capacitors? They should ALL be replaced.
Try substituting the 39/44 IF tube with a known good one.
When you align the radio, feed it the lowest possible signal. Don't crank up your signal generator to maximum - turn up the volume control on your radio instead. Preferably, use a meter or oscilloscope for alignment, connected between the AVC line and ground. If you go by this schematic:
http://www.philcoradio.com/tech/89evol.htm
connect the NEGATIVE lead of your meter or scope to the end of resistor (21) that connects to the 1st IF secondary, and the positive lead to ground. If a meter is used, set it to the low volts range. A digital meter is not good for this; an older analog meter is much better for alignment purposes. And the oscilloscope is the best way to go, if you have one.
Using the same schematic suggested above, check resistors (18 ), (30) & (31) and be sure they are within tolerance. If not, replace. All resistors in the set should be checked to be sure they are within 20% of rated values. If not, replace them.
Only other problem I can think of would be one of the IF transformers may have gone bad - the windings are wound on a wooden form, and sealed in place with wax. Sometimes, one winding will come loose and slip down on the form, closer to the other winding. This upsets the "Q" of the circuit and causes problems.
Did you replace the paper and electrolytic capacitors? They should ALL be replaced.
Try substituting the 39/44 IF tube with a known good one.
When you align the radio, feed it the lowest possible signal. Don't crank up your signal generator to maximum - turn up the volume control on your radio instead. Preferably, use a meter or oscilloscope for alignment, connected between the AVC line and ground. If you go by this schematic:
http://www.philcoradio.com/tech/89evol.htm
connect the NEGATIVE lead of your meter or scope to the end of resistor (21) that connects to the 1st IF secondary, and the positive lead to ground. If a meter is used, set it to the low volts range. A digital meter is not good for this; an older analog meter is much better for alignment purposes. And the oscilloscope is the best way to go, if you have one.
Using the same schematic suggested above, check resistors (18 ), (30) & (31) and be sure they are within tolerance. If not, replace. All resistors in the set should be checked to be sure they are within 20% of rated values. If not, replace them.
Only other problem I can think of would be one of the IF transformers may have gone bad - the windings are wound on a wooden form, and sealed in place with wax. Sometimes, one winding will come loose and slip down on the form, closer to the other winding. This upsets the "Q" of the circuit and causes problems.
--
Ron Ramirez
Ferdinand IN
