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Post subject: Twin Reverb has distortion on Channel 2
Posted: Fri Aug 25, 2017 10:07 am
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Joined: Fri Aug 25, 2017 9:49 am
Posts: 1
Location: California
Hello-

I have a late 70's SFTR that has distortion on channel two only.
If I turn the volume knob past 2.5 it distorts and the more I turn it up, the more distortion I have.

I plug in to channel 1 and it is clean all the way up (at least as far as I can turn it up without making my ears bleed).

I have NOS sylvania and Ratheon black plate pream tubes and swaped them out with known good tubes and the distortion is the same.

Wondering if anyone else has run into this issue or if the amp was modded somehow?

Thanks for any help!


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Post subject: Re: Twin Reverb has distortion on Channel 2
Posted: Tue Aug 29, 2017 7:21 pm
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Joined: Tue Nov 27, 2012 6:56 am
Posts: 1677
Location: Coastal Bend, Tx.
A good picture of the chassis components would help considerably.
Have you tried known good tubes in all positions, not just V1&V2?
Its 40 years old, it may be time for a thorough checkup by a good tech.
I would say its a good DIY experience, if your comfortable and have the necessary tools.


Last edited by sfceric64 on Wed Aug 30, 2017 7:24 am, edited 1 time in total.

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Post subject: Re: Twin Reverb has distortion on Channel 2
Posted: Wed Aug 30, 2017 1:15 am
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Joined: Fri Feb 05, 2010 4:31 am
Posts: 14045
Location: Province de Québec, Canada
Silverface Twin Reverb use AA769 or AA270 schematic.

V1 and V2 are only use on each channel, all other tubes deserve both channels

Tubes you trie may not be good. Put chan 1 , V1, V2 on chan 2, V1, V2

Or channel 1 tubes are weak and don't give distortion; distortion on both channel is another story.

Did you see this amp working fine before ? Or you just buy it like that ?


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