Having a strange problem with the oscillator in a Philco 41-290.
The oscillator seems to work OK until you tune down to 600 KC or so on the dial, then it drops frequency suddenly (or quits, can't quite tell which). I've checked for shorts in the tuning capacitor (none), cleaned the tube socket, replaced the 7A4, cleaned the band switch again,
replaced the 84 pF cap (part 19), verified the 22K resistors (parts 23 and 14) and 10K resistor (part 22) are OK; and as far as I can tell, all the trimmer caps are OK.

I'm absolutely stymied on this one and would appreciate any suggestions!

thanks, Joe W9TXU

Joe

Check the voltage on pin #6 of your oscillator when it acts strange. Voltage will be several volts negative when the oscillator is operating.

You can put another radio next to your philco tuned to the low end of the dial. The oscillator will couple without a direct connection. See if the Philco will pick up stations around 600 this way?

Can the push buttons be tuned to 600?

If each section of you tuner is the same your radio will have a padder cap. It will look like a large trimmer, usually mounted under the chassis.. This cap is used to align the low end of the dial. Tune the radio to the lowest frequency you receive, adjust the padder for the loudest signal while rocking tuning back and forth.

Norm

: Having a strange problem with the oscillator in a Philco 41-290.
: The oscillator seems to work OK until you tune down to 600 KC or so on the dial, then it drops frequency suddenly (or quits, can't quite tell which). I've checked for shorts in the tuning capacitor (none), cleaned the tube socket, replaced the 7A4, cleaned the band switch again,
: replaced the 84 pF cap (part 19), verified the 22K resistors (parts 23 and 14) and 10K resistor (part 22) are OK; and as far as I can tell, all the trimmer caps are OK.

: I'm absolutely stymied on this one and would appreciate any suggestions!

: thanks, Joe W9TXU