old Decade amp saturation channel issue

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danzigdan
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old Decade amp saturation channel issue

Post by danzigdan » Thu Jun 01, 2023 8:09 pm

Hello all, I’m wondering if anyone has seen this issue on a Decade amp or any older Peavey with a saturation input channel.

My Decade sounds fine on the clean channel, but when I plug into the saturation channel it doesn’t sound like it’s working correctly. It almost sounds like an effect pedal where the battery is almost dead and you only get about 25% of the potential of what it should sound like. I’m getting some of the saturation effect but not all.

I did take the chassis out to see if anything looked incorrect including the solder joints to that input. I’m not noticing anything. I saw a few posts on the ssguitar (solid state amp) website about the saturation stage being like the clipping stage of a distortion pedal (more or less). Could one of those components be failing?

Thanks for any help anyone might provide.

-Dan

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Pappy B
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Re: old Decade amp saturation channel issue

Post by Pappy B » Thu Jun 08, 2023 9:05 am

Both of the input jacks have small contact switches in them. With the chassis pulled out insert your guitar cable in each jack and spray those contacts with contact spray. While your at it spray the pots also. There is a 4558 opamp in there. If it is in a socket, remove it , clean the legs and socket with contact cleaner then put it back in. Be careful, the legs bend easily and put it back in turned the same way it came out. I mark mine with a Sharpie. Or if you have some opamps on hand try a different one.

If this doesn't fix the problem it's still good maintenance. Components I would check would be the electrolytic capacitors and the diodes.
The more I learn the more I realize how much I don't know.

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dak
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Re: old Decade amp saturation channel issue

Post by dak » Thu Jun 08, 2023 10:24 am

Pappy B wrote:
Thu Jun 08, 2023 9:05 am
There is a 4558 opamp in there. If it is in a socket, remove it , clean the legs and socket with contact cleaner then put it back in. Be careful, the legs bend easily and put it back in turned the same way it came out.
Pulling ICs is a question of technique so that it doesn't pull with a jolt when you overcome the rest friction (more likely than not acerbated by corrosion). Using flat tweezers or a flat screwdriver for leveraging from below, maybe alternating sides until it is loose everywhere, is what usually works for me. The leveraging makes for much better controlled movement.

danzigdan
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Re: old Decade amp saturation channel issue

Post by danzigdan » Fri Jun 09, 2023 4:51 pm

Thanks for all of the advice. I'll give it another look this evening. I'm fairly handy, but if it looks above my pay grade, I have an "amp guy" that may be able to look at it at some point.

jackjofi
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Re: old Decade amp saturation channel issue

Post by jackjofi » Sun Oct 01, 2023 3:25 am

Consider checking the electrolytic capacitors in the saturation stage, as they can affect the clipping characteristics. Also, inspect for any aging resistors or transistors in that section. A failing component might indeed be the cause. Good luck troubleshooting!JTWhatsapp

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