Tube Radio HUMMING no stations or static...

[T23]

I just got a tube radio in made by "Airline" it comes on but there are no stations and a loud hum, all tubes light.

Instead of a variable cap. it has a coil with a rod that slides in and out....odd....

Any ideas?

T23

 

[office888]

Bad electrolytic caps is common.

 

[Captain Kilowatt]

Bad electrolytic caps is common.

Agreed. Sounds like the filter capacitors in the power supply section are bad.

 

[T23]

This is an in-line filament radio, it gets power directly from power mains...

So basically I need to convert the older capacitor values to newer values and replace these paper-wax capacitors?


T23

 

[office888]

So basically I need to convert the older capacitor values to newer values and replace these paper-wax capacitors?
T23

:blink:

Yes!

I got a Heathkit DX40, and powered it up like a moron without checking anything. After ~1 minute of me tuning it into a dummy load, the 6146 final decided to go out.

I went through it, and discovered quite a few of the caps were well out of tolerance. Two of the main power supply caps were bouncing in the range of 300v - 500v, even though they're supposed to be 400v caps.

I replaced them with modern electrolytics, and now they're both solid at ~402v. She purrs beautifully on CW, although I still need to do some work on the MIC side of the circuit.

It's safe to say, if there's a paper capacitor in there, it probably needs to be replaced. Wire-wound resistors MAY be finicky too, but that's far less likely. Also check for bad solder joints.

You can go two ways

1.) Damn authenticity, and just solder in a modern equivalent

2.) De-core the paper capacitor, and put your modern caps inside it. Then reassemble the paper cap, and it looks original.

Good luck with your project. :laugh: