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Really strange Master volume in my Classic 20

8/11/1999 5:16 PM
Really strange Master volume in my Classic 20
Hi !  
Don't be afraid of all the mistakes you're going to read: I'm just french (you know, those pretentious people...)  
My Classic 20 master volume behaves strangelly:  
- at 0, I can hear my guitar but the sound is "thin". Sounds like a phase-cancellation thing.  
- going to 2, the sound progressively fades out and at 2,no sound at all. Just what it should do at 0.  
- then,it works normally  
Moreover, sometimes, when I'm playing, the volume increases ITSELF and my amp works normally after this (no sound at 0)  
My amp retailer told me it must be a defective pot. I'm not sure of it after viewing the schematic at Steve Ahola's site.  
Has anyone seen this kind of problem before?
8/11/1999 6:13 PM

It does sort of sound like you may have a defective pot in there. I'd go ahead and replace it with a pot of the same value. Just take notes are to where the wires were connected to the pot.  
Good luck!  
8/11/1999 6:22 PM

Thank you, Trace!  
I'll check the Steve Ahola project (Classic 20-> AC 30 TB) and change this defective pot.
8/11/1999 10:57 PM

Anytime! :-) Let me know if this cured your problem. You can also try and spray the pot with some good contact cleaner. Craig makes a good few good cleaners. "CAILUBE MCL" works great for pots.  
8/12/1999 7:23 AM

I'll try to clean the contacts before changing the pot. I'll tell you if it works not really soon because those charged caps in the power supply fright me... (not really sure about safety procedure and I will do it only when I'm TOTALLY sure !). And I must purchase a soldering iron first (not before 08/24/99)...  
Thank you for your help !
8/12/1999 7:18 AM
Steve A.

    Just take  
notes are to where the wires were connected to the pot.
    Wires? I guess you don't get inside these new-fangled pcb amps too much... < g >  
    The cleaner may help but it could be something else in the circuit acting up. I always figure it is cheaper to replace the part you think is bad than paying someone else to guess... And if you are wrong, well, you now have a spare part that might come in handy later.  
Steve Ahola  
P.S. The Classic 20 probably uses special OEM pots (like the C30 and C50) but you can make a 7/8" diameter generic pot work (as I explained in a post to you in the Open Forum).
8/12/1999 1:34 PM

"Wires? I guess you don't get inside these new-fangled pcb amps too much... < g >"
Ok, ok, ....(ha, ha) you got me good Steve :-) All's fair in "love & amps" as the say! (ha, ha)  
I should have said make sure you note where things were connected before you remove more than one part and forget exactly how it was connected to begin with. it saves a lot of time and headaches :-) (can you tell i've done it a few times? ha, ha)  
Actually though you are right. I don't get inside Peavey's, the latest Marshalls, etc....only if I really have to. I've been mighty lucky that I can be a little picky as to what I work on but who knows how long that will last! ;-)  
Wires rule!!  

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