Rebel 30 112 COMBO VOLUME PROBLEM

  • Thread starter Thread starter Fathernature1959
  • Start date Start date
F

Fathernature1959

New member
My Rebel 30 112 combo normally runs ok and sounds terrific, but will occasionally get real loud if I'm playing at low volume and the volume control will lose most of its ability to control the overall volume on the overdrive channel, but the gain control still seems to work like normal. It sounds almost like the master volume pot is almost wide open no matter where it is set at. Even if the master volume is all the way down there is still sound coming out of the speaker, albeit thin sounding, but will go quiet if I turn the gain volume down. I fliped the Bright/Deep switches tonight and it seemed to clear the problem but that may have just been a coincidence. The problem doesn't seem to affect the clean channel. Maybe a bad peamp tube(?), and is there a preamp tube that is used in the overdrive channel but not used in the clean channel? Any clues???? :confused:
 
I had the same thought about a cold solder joint, but I was hoping someone out here or Bruce himself had seen the same problem before and had a fix (hopefully a simple one). I may pull a couple of preamp tubes out of the Marshall that I know work good and put them into V1 & V2. Thanks for replying back to me Steedee.
 
My Rebel 30 112 combo had a either a loose element or a cracked resistive trace on its Master volume control (due to someone applying pressure or an impact on the volume knob). It would apparently work normally up to a point and then zip up to a very high volume past that point.

I got mine to work by applying pressure to the tabs on the rear of the control (the frame tabs that hold the pot together) and it has been working fine for 6 months!

Of course, you have to get into the internal circuitry which is potentially a warranty killer. My amp was purchased "used" (and non-functional... it was a multi-problem shipping-damaged lemon so I got it cheap) so I had no expectation of warranty coverage.


Steve
 
The same problem happened again tonight with my amp while I was noodling around. When I started to take the screws out of the upper back plate to have a look inside, I noticed the problem went away when the screw closest to the master volume on Ch.2 was loosened. I tightened it back up and the problem came back. Either the screw is too long and touching something near the ch.2 master volume circuit, or it's pulling on something when tightened snug.

I'll need to look at it tomorrow after work. I have a hunch that the screw is a little too long and is touching something in the circuit. I hope that is the problem because I can get some shorter screws and CASE CLOSED!

Thanks to you guys for replying with your thoughts. :thumbsup:

Bob
https://www.myspace.com/magaliajamband
 
As always......contact nate@egnateramps.com This is not normal. I do not believe you will find the screw hitting something. You may have a broken pot, which is covered under warranty.
 
Bruce,
I finally got a chance to take the back off the amp last night when the same problem returned, and I did see there was plenty of room behind the screws, so that wasn't an issue. It appeared to be the overdrive channel volume pot nut was loose in the chassis. I tightened the nut down and it stopped the problem. I suppose when I tightened the rear screws down, it slightly pulled on the chassis and the volume pot lost its good ground. All this over a loose NUT! :doh:

With a bad ground, the master volume was basically non-functional except for about the last 1/4 of its range, and the first 3/4 range of the pot made the amp sound very thin like my Les Paul had "Lipstick" pickups in it. Now all is well, and the Les Paul is fat once again. Does this scenario seem to be the symptom of a badly grounded master volume pot???

Thanks for the reply,

Bob Vincent
 
The pots do not rely on the physical chassis ground to work. I still contend there is something wrong with the amp and should be properly repaired. Be sure the problem will reoccur until you have it fixed. Please contact nate@egnateramps.com. This type of problem resolution is something I see quite often. Someone buys an amp and a problem shows up. They go onto forums looking for the solution. Most of the suggestions from other well intended players are, unfortunately, typically not correct. Now the new amp still has the problem after all the suggestions fail. I have seen people replace entire sets of tubes in brand new amps in an attempt to fix an issue when the problem was not a tube at all. Now this has dragged on for a few weeks and the owner is frustrated. This person is angry at the manufacturer and bad mouths the product and the company because they spent money on new tubes, etc. and the trouble is still there. If you bought a new TV, or a car or ??, and something went wrong, would you try to fix it yourself? Wouldn't you contact the dealer you bought it from? Most amp companies (unlike TVs and cars) have an easy way to contact the manufacturer directly for problems. I still insist the owners contact the company right away when a problem comes up, before the frustration sets in.
 
Before I tightened up the nut, I could push on the circuit board near the master pot and the problem would go away with pressure on the board. I was thinking that it may have been moving the ground on the pot enough to make good contact, but now I think it must be a cracked trace on the board or a bad solder joint on or near where the pot is attached to the board. With the nut tightened, it is holding well for now, but I will need to make the fix permanent. I don't like broken solder joints whether working well or not.

The warranty is void as I bought the amp from Musician's Friend as a used unit early this year, so I'll have to pull the board myself and do some continuity tests on the solder points.

Once again, thank you for your reply Bruce, and I'll have this fixed soon enough. I don't hold the manufacture responsible for the problem. The loose potentiometer nut that I wasn't aware of until recently probably allowed the pot to move back and forth over time enough to crack the solder joint where it attaches. That's an easy fix, and if the pot is bad, that's also an easy fix.

Bob
 
You must log in or register to reply here.
Back
Top