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Old 15th January 2009, 05:32 AM   #1
Electar is offline Electar  United States
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Question distortion at low volume

I have an old guitar amp that is only 5 or so watts. It has an 80,6l6 and a 6sj7. a field coil speaker. I can play it for about 20 minutes at any volume and it sounds fine ,then it starts distorting .with the volume low!
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Old 15th January 2009, 09:33 AM   #2
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Do you know the manufacturer or model of the amp?. First suspect in all old amps are electrolytic capacitors. Could also be old resistors drifting with heat? Need more info on it.
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Old 15th January 2009, 10:41 AM   #3
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Hi,

If it's that old that it has a field coil speaker, a recap job is in order, as mentioned.

Cheers!
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Old 15th January 2009, 10:47 AM   #4
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Could be a capacitor on the cathode of the output tube that is shorting. This would cause the tube to draw excessive current.
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Old 15th January 2009, 01:19 PM   #5
Electar is offline Electar  United States
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Its a 1939 Epiphone amp, someone has changed the filter caps already to 20 uf 450vdc theres only 2 of em. the rest of the caps are very early.
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Old 15th January 2009, 02:14 PM   #6
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Quote:
Originally posted by Electar
Its a 1939 Epiphone amp, someone has changed the filter caps already to 20 uf 450vdc theres only 2 of em. the rest of the caps are very early.
The rest of the caps are very leaky. Replace them. Another possibility is a 6L6 with grid leakage when hot. But that usually doesn't take 20 minutes to show up.
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Old 15th January 2009, 07:08 PM   #7
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Been digging around google looking for pre Gibson Epiphone schematics for nearly an hour with no luck. Got me curious what the differences were in them before Gibson bought them out.
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Old 21st January 2009, 07:39 AM   #8
Electar is offline Electar  United States
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Thanks, it makes prefect sense.
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