Crate guitar amp switching from dirty to clean, like a short or something

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That is probably a momentary switch that is dirty and sticking. These onboard effects on guitar amps are usually nothing more than a computer sound card and I've found bad connections going to and from them as well. I do think that switch is dirty and sticking, though.

I had a Crate G120C XL COmbo amp that was only outputting very quietly. I checked all pots. They were operating as they should be. I checked the speakers outs, the footswitch and its connections and both guitar inputs ..all operational. Problem: turns out when you plug an effect into the effects loop, there is an internal switch that lets the rest of the circuitry know an effect is there and routs the correct internal signal to it. As soon as I plugged in a pedal, Voila!!!! Full volume was completely resorted, no problem at all. So at this point I can either limp along with a pedal in the loop that isn't even doing anything, or I can go inside and repair the switch OR bypass it (short it out) so the loop is no longer functional.
There are other situations that can cause the same symptoms, but this is what was happening in this particular case. Amp cost me $50, sold it for $225. Nice. Got me another one-- almost same low price.

NEVER use switch cleaner such as DeOxit on pots !!!!!

I have used CRC226 available at Home Depot electrical dept.

I SUSPECT that the resistance element in that pot is cracked. This is common if the knob sustained a hit. Replacing the pot is the only cure if the element is cracked.

Reviewing the schematic, ALL audio passes through the wiper on the HIGH tone pots. If the wiper is intermittent, so will be the sound.

If your unit is solid state amp, the pot looks like a 10K ohm LINEAR taper.
If you have a tube type, then the pot is a 250K ohm LINEAR.

Note that the other tone pots in the units are AUDIO tapers, but the high is a linear taper.

Get repair parts from either DigiKey.com or Mouser.com

Not good. If you have electronics experience, you can replace the power amp IC to fix it.
Paul

When a piece of equipment causes a fuse to blow or a breaker to trip, it normally means something in the equipment's circuit was shorted. Either because of heat, moisture, a loose screw, loose wire, loose part, a bug, etc. For safety reasons, don't plug it back in and take it to a repair shop.

Hope this helps!

You can try Loud Technologies @ 866-858-5832, [email protected].

They hooked me up with parts and schematic for my Crate G212XL.

guitar amps are all set to a low Z resistance configuration. wich are made for guitar only. make sure you are using the right cables.
you need sheilded guitar cable not unshielded speaker cable in many cases these cables look exactly the same. look at your cable look for the words speaker or instrument. you need the instrument cable. if you still have that problem. then you may just not be satisfied with the quality of the amp it self.

turn that ****** on and get a can of freeze spray. coming and going type issues is usually related to a failing electrolytic capacitor. there may also be a bad mosfet, rectifier, diode, etc. i would be suspect to caps. schematics probably only available thru crate and you have to pay a couple bucks, but trust me its worth the couple bucks spent and having it on its way than wasting hours online not getting anywhere. by the way i checked my sources and came up with nada.
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