Grateful Dead Music Forum

I have an older Carvin Valve Master 100 Series amp head. On both the clean and distorted channels, the volume cracks in and out when you turn it up. When it is set on a volume, it will fade in and out randomly. It also does this on the distorted channel, but not as much as the clean. What could this problem be, and how can I fix it?
-Space

Dirty pots

Thats what i was thinking. Can i just buy new ones?

Spray some contact cleaner in there and work that shit out!

Spray it on the pots?

the volume cracks in and out when you turn it up.

When it is set on a volume, it will fade in and out randomly.

First off, if I'm reading it correctly, you have 2 different issues going on: 1. The cracking when turning the volume up is likely dirty pots as others have said, an easy fix. 2. Volume fading in and out is harder to trace, but I'd start with the Power Tubes, NOT the pre-amp tubes. How old are the power amp tubes?

BTW, that's a dam nice, cool amp. Is this the one you have?

http://www.carvinmuseum.com/decade/images/95-vm100.html

Just a tip, don't use contact cleaner on pots. Use tuner/potentiometer cleaner, it has special lubricants to prevent the pot from wearing out. Contact cleaner. without lubricants,will cause the resistive coating to wear out due to friction.

Spray it into the pots, not onto the pots. There should be space near where the wires are connected.

Crackling from the pots can also be caused by DC voltage being present on the pots due to bad capacitors.

It is an older amp. I don't think the tubes have ever been changed. It is that amp in the picture. I will try to clean the pots first. Where can i get the cleaner?

You can get tuner/potentiometer cleaner at any Radio Shack or another electronics store.

And if that doesn't solve the fading problem, which I suspect it won't, its time for new pre-amp and power-amp tubes. Your tubes could be 15 years old, right?...It's time. Yer amp will sound amazingly new, bright, and sweet again. I see it can take 6L6s or EL34 power tubes, cool...desicions, decisions. Like I said, I think you have a dam nice amp there, hang onto it.

Depending on how old the amp is, and how much (actually how little) it has been played you might want to consider a cap job also.

What exactly is a "cap" job?

You replace all of the electrolytic capacitors. They degrade with age, especially if they are not powered up often. Most have a designed life of about 15 years but usually end up lasting over 20 years if the amp is used regularly.

Hey Guys,
I just left my band and so I will have to give up my user name and use a new one. From now on I'll be loging-in as steve6string. New package, Same old person.

Steve6string:

Just a suggestion: you might want to put your handle change over in introductions. I think more people will see it there than in a far-off thread on amp problems.

Mick

Thanks Mick. Good idea. I've gone ahead and done that.

-s