09-01-2013, 07:30 PM
Yes, this radio has an XXL Converter, which I replaced with a NOS tube last December. It's still good.
I just busted out the signal generator and O-scope. Went to the oscillator plate first- good signal, frequency varies with tuning gang.
Next, I checked the converter plate- nice signal there.
Moving on, plate of the first IF amp- nada, zip, zero.
Checked the grid- nice signal. Looks like a bad 7B7.
This set has two 7B7 IF amps, which makes eliminating faults in the associated circuitry a bit easier by swapping positions. So I swapped them and checked the first IF amp with the other tube in there. Good plate signal and even some reduced volume audio tone coming out of the speaker. Bad tube for sure.
Wow, it's almost like I know what I'm doing.
I just busted out the signal generator and O-scope. Went to the oscillator plate first- good signal, frequency varies with tuning gang.
Next, I checked the converter plate- nice signal there.
Moving on, plate of the first IF amp- nada, zip, zero.
Checked the grid- nice signal. Looks like a bad 7B7.
This set has two 7B7 IF amps, which makes eliminating faults in the associated circuitry a bit easier by swapping positions. So I swapped them and checked the first IF amp with the other tube in there. Good plate signal and even some reduced volume audio tone coming out of the speaker. Bad tube for sure.
Wow, it's almost like I know what I'm doing.
It's not how bad you mess up, it's how well you can recover.
