Hello!!
I am working on a GE 501 chassis. There is nothing but static up and down the dial. The static changes with the volume control. I have recapped the chassis. I checked the ant input to pin 8 of the 12SA7 converter tube. I applied a modulated 445khz signal and was heard at the speaker. Next I check the voltage on pin 5(the oscillator input), the voltage read -10volts. Where can I look now?? Any ideas?? There are no stations playing.
Thank you for any help!!
Daniel

Hi Daniel :

It sure, kind-of sounds like a silver-mica-disease type problem... if you are experiencing loud crashing static sounds.... like lighting-type static sounds.

Does your chassis use those slug-tuned IF transformers?

I don't believe it did... but there just may have been a production change.
But if your IF cans use the separate cap trimmers then... you have nothing to worry about SMD.

Otherwise ... I can't think of why you'd have steady static and no stations.

:Hi Daniel :
:
:It sure, kind-of sounds like a silver-mica-disease type problem... if you are experiencing loud crashing static sounds.... like lighting-type static sounds.
:
:Does your chassis use those slug-tuned IF transformers?
:
:I don't believe it did... but there just may have been a production change.
:But if your IF cans use the separate cap trimmers then... you have nothing to worry about SMD.
:
:Otherwise ... I can't think of why you'd have steady static and no stations.
:
Also:
You may be able to determine if the osc is running if you place another good-working radio next to it and tune it for around 14500khz (455khz higher than the other radio)
Then try tuning this GE501 radio to around 1000khz and the good radio should be able to hear the heterodyne sounds if this GE501 osc is running.

Exactly where did you apply the "445 KHz" signal? Is "445 KHz" a typo?

The IF frequency for this set is 455 KHz, so if you used 445K to peak the IF transformers, that could cause the set to reject the mixed signal, resulting in no reception.

CV:
I'm not sure I understand what you mean.
That is the way the IFs work. The mixer uses the RF signal and local-osc to produce 4 frequecies:
... The sum, the difference and the original two.

So 455khz is the difference... right?
So 455khz is the correct freq with which to align the IFs.

Even if a strong modulated 455khz were applied at the ant it can be heard at the speaker and the IFs can be peaked for that.

It's usually applied to the grid of the rf amp/mixer.

Yes, for this set 455 KHz is the IF frequency. 445 KHz is not. I was attempting to ascertain if Daniel actually injected a modulated 445 KHz (as he stated) or if he just fatfingered a keystroke and was really injecting a tone-modulated 455 KHz, which would be the logical thing to do if one wanted to check signal processing past the mixer stage.

Since the IF RC circuits are finely tuned (presumably) to pass only 455 KHZ and reject all other frequencies, if they were passing 445 KHz, something is out of whack. Hence my questions as to whether or not he was actually injecting 445 KHZ, and exactly where it was being applied.