noise question related to 6a8g tube

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noise question related to 6a8g tube

Post by foxcovert on Fri Apr 29, 2011 5:35 pm

Restoring my first radio, a GE G53. Got it mostly rewired and completely recapped. It plays great except for one quirk. If I very lightly tap on the 6A8G tube, which is defined in the schematic as the converter and oscillator, i get a hissing sound with each tap. I checked the connections and the tube socket. No problems. I also discovered that if I tilt the chassis, the hissing is constant. It's a very faint hiss, not even close to covering up the signal. Could it be a problem within the tube simply requiring replacement to cure the problem?

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Re: noise question related to 6a8g tube

Post by Bill Cahill on Fri Apr 29, 2011 8:54 pm

Dirty tube socket pins?
Try using electronic spray cleaner on socket, and, tube pins. Wiggling tube will also cause noise on dirty sockets.
If not that, tube is bad.
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Re: noise question related to 6a8g tube

Post by foxcovert on Wed May 11, 2011 3:37 pm

It was the tube. And what a difference the new tube made. Now to get on with alignment. It's obvious someone thought the adjustment screws were "loose" and needed to be tightened down.

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Re: noise question related to 6a8g tube

Post by Bill Cahill on Wed May 11, 2011 7:46 pm

Congrats!
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Re: noise question related to 6a8g tube

Post by Resistance is Futile on Thu May 12, 2011 12:14 pm

Wait. affraid
What do you mean, adjustment screws?Suspect
You don't tighten adjustment screws. pale
They are set to a certain capacitance, by adjustments and if slug tuned coils, an inductance balance to align the IF transformers, Rf Transformers, Oscillator and RF variable capacitors to make them track. If you change those you may be sorry (unless you have had previous experience) study

Most screws are one of two types, one to adjust a capacitance, the other type is a screw attached to an adjustable iron powdered core.

These are needed to bring the alignment of stages, to make the dial track correctly and increase sensitivity and bandwidth.
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Re: noise question related to 6a8g tube

Post by jerryhawthorne on Tue Jan 29, 2013 6:17 pm

Fox, if it plays great now and the stations track the dial, unless you have the test equipment to do a full alignment don't mess with it! If anyone had the magic screwdriver in the past to "tighten" down those adjusting screws, you would have a VERY poorly working on non working radio. Perhaps the tube only solved the hissing noise?
Jerry


Last edited by jerryhawthorne on Tue Jan 29, 2013 6:20 pm; edited 1 time in total (Reason for editing : Added the last bit)

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