Did you clean the tube pins on this radio? Put WD-40 on pins with a Q tip, then plug tube in and out of its socket several times while the pins are wet. Often clears up static problems. Do this first.
Okay, here's my Rube Goldberg idea for finding out if the IF section of your Admiral is tuned correctly. This is going to use another operating radio that you
know has a 455 Kc IF section.
These superhetrodyne sets convert any incoming signal to an intermediate frequency (IF) and then amplify it in the IF stage. The stage consists of the input IF transformer, the IF tube, and the output IF transformer. The only signal that ever goes through there is supposed to be 455 Kc (or KHz, if you must!)
So if we inject 455 Khz into the Admiral's IF stage, and get nothing from the Admiral's speaker, then the IF transformers are maladjusted, the tube is bad, or there is some component problem.
The admiral IF tube is the 7A7. If you scratch a piece of wire on pin 6 you should get some scratching out of the speaker, meaning the tube is probably alive.
We can use another operating radio with a 455 Khz IF section as a signal generator to get the Admiral IF stage on the right frequency. If you have another tube set with such an IF, it would help if you could give the make/model and track down the schematic. And don't shock yourself if the other radio is AC/DC.
Yikes. Do you know the precautions?
First, pull out the 6SA7 tube. It's not needed for IF adjustments using this method and could just cause interference. Turn the bandswitch to broadcast band.
Take a piece of insulated wire not more than a foot long and tape the ends of it, don't want any wire showing. Place one end of the wire near the plate connection of the other radio's IF tube. Hold in place with a wooden clothespin, whatever, insulated method. The other end of the wire will go alongside of the wire going to pin 6 of the Admiral 7A7, hold in place. There is no direct connection, just transfer of the signal by proximity. The wire insulation is like the dielectric of a capacitor, it's really a capacitor transfer.
Tune the operating radio to any station and then turn its volume down so you can't hear it. Turn the volume up on the Admiral and if the IF is adjusted right, you'll hear the station from the other radio on the Admiral's speaker. If you do or if you don't, try adjusting the trimmers on the second IF transformer (the one between the 7A7 and the 6SQ7) for loudest signal. If the signal is too loud to hear a pronounced peak, uncouple the wire a bit farther away from the 7A7 grid. Take it as far away as you can and still hear a tiny signal. A weak signal is best for peaking.
Now move the wire from the 7A7 grid to proximity of the wire from pin 3 of the 6SA7 socket and adjust trimmers on the other (first) IF transformer. Make the signal as weak as possible by moving the wire away from the 6SA7 socket and go over both sets of IF transformer trimmers again to find the best peak on the weakest signal.
If you get this far with signals coming through, take the wire away, shut off the other radio, and plug the 6SA7 back in. There may be stations heard, whether strong or not, whether at the right place on the dial or not. Then we'll trudge on from there.
¡Whew! Report back, trooper.
