Tube radios sound great when cold.

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Tube radios sound great when cold.

Post by Sir Henry on Tue Nov 01, 2016 1:37 pm

I've noticed my radios sound great when first turned on but after an hour I get static and hum. Two appear to have new tubes and the other two have dusty ones.

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Re: Tube radios sound great when cold.

Post by 75X11 on Tue Nov 01, 2016 2:56 pm

Have you done any electronic restoration on your radios? If you have not replaced your old paper and electrolytic filter capacitors, that may be the source of the noise. They can fail abruptly and sometimes with damage to other parts they filter.
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Re: Tube radios sound great when cold.

Post by Sir Henry on Tue Nov 01, 2016 6:37 pm

75X11 wrote:Have you done any electronic restoration on your radios?  If you have not replaced your old paper and electrolytic filter capacitors, that may be the source of the noise.  They can fail abruptly and sometimes with damage to other parts they filter.

I have not done any restoration but I see new tubes in two of my radios. One keeps a clear sound for hours while the other one doesn't. Plus I have two others with old dusty tubes.

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Re: Tube radios sound great when cold.

Post by 75X11 on Tue Nov 01, 2016 6:55 pm

Well, the radios have electrolytic capacitors that work somewhat like batteries. they are what filter out the hum in the power supply. When they get old the chemicals in them begin to dry out and not only do they lose their effectiveness, but can develop an internal short and fail violently. It is strongly advised to replace those and the paper capacitors in the radios, for safety's sake. That also makes the unit operate quieter.
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Re: Tube radios sound great when cold.

Post by 75X11 on Tue Nov 01, 2016 6:57 pm

Also, the dirt on the outside of the tube shouldn't affect the operation of the tube much.
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Re: Tube radios sound great when cold.

Post by Sir Henry on Tue Nov 01, 2016 7:07 pm

75X11 wrote:Well, the radios have electrolytic capacitors that work somewhat like batteries.  they are what filter out the hum in the power supply.  When they get old the chemicals in them begin to dry out and not only do they lose their effectiveness, but can develop an internal short and fail violently.  It is strongly advised to replace those and the paper capacitors in the radios, for safety's sake.  That also makes the unit operate quieter.

Is this something a novice can do? I've also noticed on three of the radios that when I turn the station dial I get a lot of dirty noise.

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Re: Tube radios sound great when cold.

Post by 75X11 on Tue Nov 01, 2016 7:22 pm

Take a look here. there is some good information and will give you an idea of whether you would want to give it a try. It isn't extremely difficult, you just need to be careful and methodical as you go.

http://www.tuberadioforum.com/t1615-a-nice-resource-for-beginners
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Re: Tube radios sound great when cold.

Post by Wildcat445 on Tue Nov 01, 2016 10:34 pm

I'd bet a good tune up will improve matters greatly.

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Re: Tube radios sound great when cold.

Post by Bill Cahill on Tue Nov 01, 2016 10:40 pm

Actually, dirty tubes can't dissipate heat very well, so, in time, they usually fail quicker than when clean.

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Re: Tube radios sound great when cold.

Post by Sir Henry on Wed Nov 02, 2016 7:17 pm

Bill Cahill wrote:Actually, dirty tubes can't dissipate heat very well, so, in time, they usually fail quicker than when clean.

I was thinking the same thing. After an hour the radios began to get fairly warm.

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Re: Tube radios sound great when cold.

Post by Bill Cahill on Wed Nov 02, 2016 7:27 pm

They'll still get warm. But, the tubes can't dissipate heat well, so, they will fail faster. Whenever I restore anything with tubes I clean the tubes as well, trying to be careful not to remove any writing on the tube.

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Re: Tube radios sound great when cold.

Post by Dan Walker on Fri Nov 04, 2016 12:18 pm

On every radio I get, I start with checking the tubes , cleaning the tubes, blowing out the tuning caps and. then I check all the wiring under the chassis.. I ALWAYS CHANGE EVERY CAPACITOR in the radio.
As others have said, the electrolytic caps will fail over time.

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