RCA 118 - problem with volume

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RCA 118 - problem with volume

Post by radioland on Sat Dec 31, 2016 1:19 pm

Ok Guys, i spent weeks on this one. I restored the RCA tombstone 118 and the sound is clear across the full range of stations. I have good tubes, checked them on my tube tester. I just cannot get a decent volume out of it. It's loud enough to hear when i'm sitting by the radio but not loud enough across the room. I think the problem lies with the 6B7 as i do not register the 'scratch' sound when i touch the screen grid vs. other screen grid 6A7 etc. this is not much information but maybe it will reach someone who had the same issue with this radio. Thanks, Rich

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Re: RCA 118 - problem with volume

Post by John Bartley on Sat Dec 31, 2016 3:44 pm

If you have a way to measure output voltage, do that. The best way is probably a scope. Hook up a signal generator and select either an AF or a modulated RF depending on where you inject the signal. Check the output waveform at the plate of the audio output tube, then see if you get the same voltage profile at the output of the speaker (output) transformer. If your output from the audio final is good, then check the transformer and speaker to see if either is defective. After that, start working your way backeards thru' the set to see where the gain is being lost.

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