Fender Rumble Gain Pot

[Larry23]

I Purchased a used Fender Rumble 500 combo knowing that the gain control was not working correctly. When it is turned to full volume it works fine. All the rest of the range does not work at all. I am gigging with it with the gain all the way up. Should I replace the pot? I am pretty handy and would want to do it myself. Could it be something besides a bad pot? Should I just leave it alone?

 

[Redbrangus]

It wouldn't be too difficult to slide the chassis out to take a look-see about how difficult the task is likely to be. I haven't seen inside the Rumbles, but I know how complicated a modern electronic package can be to disassemble to the point you probably would need to. I can solder at the circuit board level, but I would anticipate choosing to take it to factory-authorized tech after making a quick check inside to be sure. Only you can evaluate how well your ability matches up to the difficulty of task -- if you can live with it, you might choose to leave it as is.

BTW, the symptom lines up pretty well with indiscriminate use of contact cleaner to clean pots.

 

[Larry23]

It wouldn't be too difficult to slide the chassis out to take a look-see about how difficult the task is likely to be. I haven't seen inside the Rumbles, but I know how complicated a modern electronic package can be to disassemble to the point you probably would need to. I can solder at the circuit board level, but I would anticipate choosing to take it to factory-authorized tech after making a quick check inside to be sure. Only you can evaluate how well your ability matches up to the difficulty of task -- if you can live with it, you might choose to leave it as is.

BTW, the symptom lines up pretty well with indiscriminate use of contact cleaner to clean pots.

Thank you so much for your reply. I ordered a can of DeoxIT. I will slide it out and look for bad solder joints and clean the pot, along with checking the input jack. Then I will put it back and move on with my VERY fortunate life. I am a little afraid to start soldering! Are you ok with DeoxIT?

 

[Redbrangus]

...the symptom lines up pretty well with indiscriminate use of contact cleaner to clean pots.

Uhmm...what I was intending to convey is the likelihood this pot has already been ruined by someone using too much contact cleaner of some sort. DeOxit D5 is what I'd recommend, but it's easy to use too much. They (Caig) have a specialized DeOxit spray intended for use on faders, but it's seriously pricey.

 

[agedhorse]

The fader lube (F-5) is not great for rotary controls. It's awfully messy unless you are super careful, and the mess is a pain to clean up afterwards unless you have a proper cleaning set-up (PCB washing machine w/ DI or distilled water final rinse and warm chamber bake dry.

You are likely at the point where the pot needs to be replaced, it's either damaged beyond salvage or cracked. Be sure you have the technique to replace properly or you may find that the resulting damage is no longer (easily) repairable.

 

[Redbrangus]

The fader lube (F-5) is not great for rotary controls. It's awfully messy unless you are super careful, and the mess is a pain to clean up afterwards unless you have a proper cleaning set-up (PCB washing machine w/ DI or distilled water final rinse and warm chamber bake dry.

You are likely at the point where the pot needs to be replaced, it's either damaged beyond salvage or cracked. Be sure you have the technique to replace properly or you may find that the resulting damage is no longer (easily) repairable.

Agree that the pot is likely beyond hope. I've been using the FN5, which doesn't seem quite so odious, but generally speaking, all that stuff is likely to do as much harm as good. In this case, where the pot is probably worthless anyway, there's probably no harm in giving it a judicious shot.

 

[agedhorse]

Judicious is in the eye of the "shooter"!

 

[Larry23]

You’re not going to believe this but someone desoldered and cut out the pot for the overdrive level. It was just screwed to the case. I cleaned the gain pot and now it works cleanly, but still just on or off. I would never use the overdrive, however the volume now since the gain is clean is way too much. I really need to cut down the preamp gain. Now I wonder why the overdrive pot was cut out and if I put it back in is something else wrong. I have two questions, besides all of you experts I’m sure will have ideas. I was wondering if I could run an external pedal or something to be able to turn the preamp gain down, or how much it would cost to buy that board new from Fender.

 

[agedhorse]

Yeah, you ended up with somebody's hack job mod. I would look to see what else may be damaged. Restoring the amp to the (fully) stock configuration is my recommendation.