Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: bogner100b on July 23, 2014, 12:49:45 PM

Title: Roland JC120 HELP!!
Post by: bogner100b on July 23, 2014, 12:49:45 PM
So we lost power on this bad boy, checked the fuse and it was bad.  Pulled the chassis the two 6amp fuses were also blown.

No resistors on the board look back, did take my meter and test several.   Anyone have any similar experiences?


Thanks
Title: Re: Roland JC120 HELP!!
Post by: ilyaa on July 23, 2014, 01:21:34 PM
might be a short somewhere -

do you have a light bulb limiter?

if not, make one and you can use it to see if there is a short somewhere in the amp -

-replace the fuses
-plug the amp into the limiter and the limiter into the wall
-turn it on
          if the bulb burns bright you have a short somewhere you gotta track down
Title: Re: Roland JC120 HELP!!
Post by: Enzo on July 23, 2014, 03:26:57 PM
QuoteAnyone have any similar experiences?

Has anyone ever had an amp blow its fuses?

Yes.


When an amp blows fuses, first thing I look for is shorted output transistors.  After that I look for shorted rectifiers in the power supply.   That covers the majority of fuse blowing.

Most bad parts do not look any different.