classic 20 channel 2 not working right

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adirhunterc
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classic 20 channel 2 not working right

Post by adirhunterc » Thu Sep 08, 2022 8:59 am

classic 20 channel 2 not working right when i first turn it on it woks right but after 20 or so minutes the volume drops out the post control don't work at all.

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JamesPaul
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Re: classic 20 channel 2 not working right

Post by JamesPaul » Fri Sep 09, 2022 11:09 pm

Welcome to the forum.

Do the TSI lights stay green, indicating no concerning issues with the power tubes?

After Channel 2 fails, does Channel 1 still operate normally?

I am not sure if I have a schematic for the Classic 20MH. Let me check and I may have a suggestion(s).
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

WrldEatr9
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Re: classic 20 channel 2 not working right

Post by WrldEatr9 » Sat Sep 10, 2022 10:58 pm

Perhaps needs a new tube in V2.

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Pappy B
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Re: classic 20 channel 2 not working right

Post by Pappy B » Sun Sep 11, 2022 11:06 am

If you have access to another amp, run your pre-amp out to the other power-amp in then the other amp's pre-amp to your power-amp in. Should be able to determine if the problem is in the pre-amp or power-amp section.
The more I learn the more I realize how much I don't know.

adirhunterc
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Re: classic 20 channel 2 not working right

Post by adirhunterc » Tue Sep 13, 2022 1:06 pm

JamesPaul wrote:
Fri Sep 09, 2022 11:09 pm
Welcome to the forum.

Do the TSI lights stay green, indicating no concerning issues with the power tubes?

After Channel 2 fails, does Channel 1 still operate normally?

I am not sure if I have a schematic for the Classic 20MH. Let me check and I may have a suggestion(s).
Both lights stays green I even changed preamp tubes it still does it

adirhunterc
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Re: classic 20 channel 2 not working right

Post by adirhunterc » Tue Sep 13, 2022 1:08 pm

WrldEatr9 wrote:
Sat Sep 10, 2022 10:58 pm
Perhaps needs a new tube in V2.
I was thinking that!

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JamesPaul
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Re: classic 20 channel 2 not working right

Post by JamesPaul » Tue Sep 13, 2022 6:53 pm

adirhunterc wrote:
Tue Sep 13, 2022 1:06 pm
JamesPaul wrote:
Fri Sep 09, 2022 11:09 pm
Welcome to the forum.

Do the TSI lights stay green, indicating no concerning issues with the power tubes?

After Channel 2 fails, does Channel 1 still operate normally?

I am not sure if I have a schematic for the Classic 20MH. Let me check and I may have a suggestion(s).
Both lights stays green I even changed preamp tubes it still does it
Does Channel 1 still operate normally after Channel 2 has failed?

If you did not start with this, it is a good first step to take a 1/4" plug, spray some Deoxit on it, and plug/unplug it a few times in every jack on the amplifier. Respray the plug before each jack. At a minimum try this on the CHNL/BOOST Footswitch jack, and the Effects Loop SEND & RETURN jacks.

I have not yet found a schematic.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

adirhunterc
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Re: classic 20 channel 2 not working right

Post by adirhunterc » Tue Sep 13, 2022 9:49 pm

JamesPaul wrote:
Tue Sep 13, 2022 6:53 pm
adirhunterc wrote:
Tue Sep 13, 2022 1:06 pm
JamesPaul wrote:
Fri Sep 09, 2022 11:09 pm
Welcome to the forum.

Do the TSI lights stay green, indicating no concerning issues with the power tubes?

After Channel 2 fails, does Channel 1 still operate normally?

I am not sure if I have a schematic for the Classic 20MH. Let me check and I may have a suggestion(s).
Both lights stays green I even changed preamp tubes it still does it
Does Channel 1 still operate normally after Channel 2 has failed? yes channel 1 still works.


If you did not start with this, it is a good first step to take a 1/4" plug, spray some Deoxit on it, and plug/unplug it a few times in every jack on the amplifier. Respray the plug before each jack. At a minimum try this on the CHNL/BOOST Footswitch jack, and the Effects Loop SEND & RETURN jacks.

I have not yet found a schematic.

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JamesPaul
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Re: classic 20 channel 2 not working right

Post by JamesPaul » Tue Sep 13, 2022 11:36 pm

adirhunterc wrote:
Tue Sep 13, 2022 9:49 pm
JamesPaul wrote:
Tue Sep 13, 2022 6:53 pm
adirhunterc wrote:
Tue Sep 13, 2022 1:06 pm


Both lights stays green I even changed preamp tubes it still does it
Does Channel 1 still operate normally after Channel 2 has failed?


If you did not start with this, it is a good first step to take a 1/4" plug, spray some Deoxit on it, and plug/unplug it a few times in every jack on the amplifier. Respray the plug before each jack. At a minimum try this on the CHNL/BOOST Footswitch jack, and the Effects Loop SEND & RETURN jacks.

I have not yet found a schematic.
yes channel 1 still works.
Okay.

Try the jack cleaning and see if Channel 2 still fails.

If it does, do you have another amp you can use to test with? Connect an instrument cable or patch cord between your Classic 20MH Effects Loop SEND jack, and the Effects Return jack, or Power Amp In jack, or even the Input jack on your test amp. Try it using the power amp setion of your test amp. Does Channel 2 still fail? I see Pappy B already recommended this. If you tried it, what were the results?

If it is still failing, the issue would seem to be in the Channel 2 preamp signal path and likely thermal related. Still I would like to see a schematic to know how the Channel switching is being accomplished.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

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