N00b Question

BearBoy · Post by **BearBoy** » Tue Sep 18, 2012 1:26 pm

I've got a Marshall DRP-1 with "scratchy" knobs. i.e. I get a crackling noise when I turn them and at some positions the sound just cuts out completely.

Does it sound like opening it up and squirting it with something like this might fix it?

Yes, I know this is probably billy basic...

Post by **Mike** » Tue Sep 18, 2012 1:30 pm

Could help if it's dirt or dust preventing the wiper contacting with the strip of resistive material, however it could be just worn through and you have dead spots - They might need replacing.

I think they're board mounted so it could be painful.

BearBoy · Post by **BearBoy** » Tue Sep 18, 2012 1:33 pm

Thanks Mike

Sounds like it's worth a go for a couple of quid. TBH I've never used it that much so hopefully they haven't worn out.

mixtape · Post by **mixtape** » Tue Sep 18, 2012 2:52 pm

Yeah, try the contact cleaner first. It has kept me from unnecessarily replacing an amp and a set of computer speakers, so you never know.

Concretebadger · Post by **Concretebadger** » Tue Sep 18, 2012 4:54 pm

I've experienced the same problem with the gain knob of my HT-5's drive channel. It goes from low to maximum at the nine O clock position and that's it. My first thought was, "oh. A dirty pot. I can just clean it..." but it's not a particularly old amp and there's no visible gap in the control panel around the knob or pot shaft where any dirt could get in. I reckon it's a bad pot, but as the bossman said: many amps these days have board-mounted pots so it's going to be a PITA to replace.

Shame really, because it's a nice little amp and I was thinking about selling it, but that's not a good idea when it's in this state.

George · Post by **George** » Tue Sep 18, 2012 6:25 pm

Concretebadger wrote:I've experienced the same problem with the gain knob of my HT-5's drive channel. It goes from low to maximum at the nine O clock position and that's it. My first thought was, "oh. A dirty pot. I can just clean it..." but it's not a particularly old amp and there's no visible gap in the control panel around the knob or pot shaft where any dirt could get in. I reckon it's a bad pot, but as the bossman said: many amps these days have board-mounted pots so it's going to be a PITA to replace.

Shame really, because it's a nice little amp and I was thinking about selling it, but that's not a good idea when it's in this state.

Something like this happened on a pedal once. It was a loose solder connection to one of the lugs.

Concretebadger · Post by **Concretebadger** » Tue Sep 18, 2012 8:39 pm

George wrote:
Concretebadger wrote:I've experienced the same problem with the gain knob of my HT-5's drive channel. It goes from low to maximum at the nine O clock position and that's it. My first thought was, "oh. A dirty pot. I can just clean it..." but it's not a particularly old amp and there's no visible gap in the control panel around the knob or pot shaft where any dirt could get in. I reckon it's a bad pot, but as the bossman said: many amps these days have board-mounted pots so it's going to be a PITA to replace.

Shame really, because it's a nice little amp and I was thinking about selling it, but that's not a good idea when it's in this state.
Something like this happened on a pedal once. It was a loose solder connection to one of the lugs.

Thanks for the suggestion - that makes more sense actually. It would explain why I'm getting the 'all or nothing' effect of a malfunctioning pot as I turn it, but none of the crackle that you'd expect from a dirty or worn one. It would be more straightforward to fix too.

Bacchus · Post by **Bacchus** » Tue Sep 18, 2012 8:56 pm

Concretebadger wrote:I've experienced the same problem with the gain knob of my HT-5's drive channel. It goes from low to maximum at the nine O clock position and that's it. My first thought was, "oh. A dirty pot. I can just clean it..." but it's not a particularly old amp and there's no visible gap in the control panel around the knob or pot shaft where any dirt could get in. I reckon it's a bad pot, but as the bossman said: many amps these days have board-mounted pots so it's going to be a PITA to replace.

Shame really, because it's a nice little amp and I was thinking about selling it, but that's not a good idea when it's in this state.

Hmmm, do some amps not have the "wrong" type of pot on the volume knob, so that most of the effective use of the knob is in the first quarter of a turn? I thought it was something to do with whether the pot was linear or logarithmic, and I always assumed it was a cynical way to make people think the amp will be really loud cranked because it gets much louder at lower settings than they expect when they are trying it out in a shop.

I thought the cheaper Fender amps did this, like the Frontman and such?

Concretebadger · Post by **Concretebadger** » Tue Sep 18, 2012 10:28 pm

BacchusPaul wrote:
Concretebadger wrote:I've experienced the same problem with the gain knob of my HT-5's drive channel. It goes from low to maximum at the nine O clock position and that's it. My first thought was, "oh. A dirty pot. I can just clean it..." but it's not a particularly old amp and there's no visible gap in the control panel around the knob or pot shaft where any dirt could get in. I reckon it's a bad pot, but as the bossman said: many amps these days have board-mounted pots so it's going to be a PITA to replace.

Shame really, because it's a nice little amp and I was thinking about selling it, but that's not a good idea when it's in this state.
Hmmm, do some amps not have the "wrong" type of pot on the volume knob, so that most of the effective use of the knob is in the first quarter of a turn? I thought it was something to do with whether the pot was linear or logarithmic, and I always assumed it was a cynical way to make people think the amp will be really loud cranked because it gets much louder at lower settings than they expect when they are trying it out in a shop.

I thought the cheaper Fender amps did this, like the Frontman and such?

I'm not sure about Fender amps, but my Blackstar's problem isn't that (it's interesting though, and I wonder if anyone's investigated that quirk in those cheaper Fender models). The gain jumps from completely clean to really distorted - it basically goes from 1 to 10 and misses out 2 to 9. My RAT's gain control used to have the 'wrong' taper pot so I think I know the issue you're outlining here, but this is definitely a damaged pot or solder joint; even a different taper will give some 'sloping' increment as you turn the knob, but this is all or nothing. It's weird; it never used to do this either, so I'm dead certain that something's wrong. George's suggestion sounds more plausible than a simple dirty/worn pot, given my amp's age.

Bacchus · Post by **Bacchus** » Tue Sep 18, 2012 10:49 pm

Ah, okay. Well, that sounds nothing like what I'm talking about.