old radio repair

themadhacker · Post by **themadhacker** » Mon Sep 15, 2008 5:48 pm

ok awhile ago I was riding my bike, when i saw a thrown out radio from the 1940s. well, I had my dad drive me back to get it. and when I plugged it in at home, after the tubes warm up, it starts making some high pitched frequency noises when changing stations. then when you hear voices, they barely sound like voices, more like staticy murmuring. so I was wondering if anybody who has knowledge of old tube radios, can they help me? I would love to get this working. BTW there is no antenna.

Post by **bicostp** » Mon Sep 15, 2008 5:51 pm

AM or FM? (Since you said 'no antenna', probably AM. They have a little coil antenna inside.)

You might have to clean the tuner part. (I think it's something along the lines of a variable capacitor.

Take the back cover off, let the tubes warm up, and turn the lights off. Do any of the tubes look dimmer than the others? If so, that one's failing. [insert deity of your choice here] help you if you need to replace a tube. Thankfully, I'm pretty sure it's a dirty or corroded tuner.

themadhacker · Post by **themadhacker** » Mon Sep 15, 2008 5:56 pm

definitely AM I don't think FM came out until much later. I wil test the tubes (don't need to take the back off cause it was missing, as well as the record player speed dial yea, the whole case is torn apart, but i can fix that)

themadhacker · Post by **themadhacker** » Mon Sep 15, 2008 6:07 pm

yep, it's the tubes. one in the middle is burning a nice glow of orange, but the two on either side of it are barely glowing at all.

Dr. KillGood · Post by **Dr. KillGood** » Mon Sep 15, 2008 7:17 pm

Should they be glowing?

themadhacker · Post by **themadhacker** » Mon Sep 15, 2008 7:30 pm

Dr. KillGood wrote:Should they be glowing?

pretty sure

nitro2k01 · Post by **nitro2k01** » Tue Sep 16, 2008 5:25 am

They should definitely be glowing. It is by heating the cathode you make it swing electrons out in the air (Or strictly speaking, vacuum)
As bicostp pointed out, the variable capacitor may still be dirty.
Also, another thing that usually breaks in old radios are the capacitors. Looks at the values of the old ones, look at new ones with the same value. You'll see how ridiculously much they have shrunk over the yeas.

timmeh87 · Post by **timmeh87** » Tue Sep 16, 2008 5:51 am

Yeah all the electrolytic caps are probably dry and in need of replacing.

themadhacker · Post by **themadhacker** » Tue Sep 16, 2008 8:48 am

so would old caps make the tubes not glow?

nitro2k01 · Post by **nitro2k01** » Tue Sep 16, 2008 8:49 am

timmeh87 wrote:Yeah all the electrolytic caps are probably dry and in need of replacing.

Not only the electrolytic ones. Other types might've suffered too.

themadhacker wrote:so would old caps make the tubes not glow?

No, but who said that your radio only has one prolem?

themadhacker · Post by **themadhacker** » Tue Sep 16, 2008 8:57 am

[quote="nitro2k01

themadhacker wrote:so would old caps make the tubes not glow?

No, but who said that your radio only has one prolem?[/quote]

the radio has many problems. the record turntable motor has fallen off into the back of the case, and the dial that lets you switch between 75 and 45 rpm is missing. it's junk, but I want to fix it.