JCM 800 Input Problem

Dax-The-Ax · Post by **Dax-The-Ax** » Sun Oct 03, 2004 11:37 pm

I was playing my JCM 800 through the high input and the sound started crackling in and out and finally, with the amp cranked, i can barely hear any sound, it is very faint. The low input works fine. Anyone have any suggestions, the amp is from 86' and has the frickin inputs and tone controls mounted on the PCB!! Ugh!!!

Post by **VelvetGeorge** » Sun Oct 03, 2004 11:43 pm

Uh OH! Sounds like an input jack may be bad. Fortunately, they're cheap. It could also be the V1 tube or a handfull of components around it.

Most likely the jack.

George

Dax · Post by **Dax** » Mon Oct 04, 2004 12:45 am

They are cheap, but getting them off the Board sucks!!

Dax · Post by **Dax** » Wed Oct 06, 2004 10:14 am

Changed the input jack, tubes and high input still not working.

Flames1950 · Post by **Flames1950** » Wed Oct 06, 2004 1:59 pm

Hey Dax, you may need to change the low input jack as well. MV amps use the switching contacts of the low input jack to make a connection between the first and second gain stages for the high input, when you stick a plug into the low input the first gain stage is now disconnected. If those contacts are dirty or bad you will not pass signal to the second gain stage using the high input anymore but your low input will still work fine. If you still have the jack you took out swap it back in for the low input and see if it helps.

Dax-The-Ax · Post by **Dax-The-Ax** » Wed Oct 06, 2004 7:53 pm

Thanks, i will try that out, these Board mounted pots and jacks are a joke! I'm very close to yanking the board , jacks and tone controls out and converting to Superlead PTP!! It's a modded bastard, anyway. It has an added effects loop, which i like, but haven't decided if i will keep it yet.

Dax-The-Ax · Post by **Dax-The-Ax** » Wed Oct 06, 2004 8:16 pm

Dude, you are a genius!! My low sensitivity's jack contacts dont spring back and touch when i remove the cable. So i plugged into the high, pushed the contact with a pencil and walah!! I may take the jacks off the board and run wires.

Thanks alot!!

Dax-The-Ax · Post by **Dax-The-Ax** » Wed Oct 06, 2004 11:49 pm

Fixed her right up. Thanks a ton for the help.