Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Hello,

I have a Marshall MG100DFX combo amp that isn't working properly. I'd appreciate any help troubleshooting and repairing this amp.

Here is the issue I'm having: When using the clean channel, I have to turn the volume and gain almost all the way up in order to hear anything. When using the overdrive channel, there is a lot of hum, as if the guitar cord was unplugged and someone was touching the tip.

Any ideas as to what the issue may be?

A quick google,, tells me it has a fancy effects loop.

Does the FX control knob have any impact on sound level?
Or turning any other (not so obvious) knobs have an effect on sound produced?

Sometimes the FX loop *Sockets* can cause loss of Volume and just by bridging those loop sockets with a guitar cord can bring it back to normal.

Just trying to cover the easy stuff first.
Phil.

Or a broken ground connection on the input jack.

Quote from: phatt on August 29, 2016, 08:23:46 AM
A quick google,, tells me it has a fancy effects loop.

Does the FX control knob have any impact on sound level?
Or turning any other (not so obvious) knobs have an effect on sound produced?

Sometimes the FX loop *Sockets* can cause loss of Volume and just by bridging those loop sockets with a guitar cord can bring it back to normal.

Just trying to cover the easy stuff first.
Phil.

Hi Phil,

The effects knob does not seem to be doing much of anything at all. The bass, treble, and mid knobs seem to be working, but just barely making a difference in the sound.

Jim

OK,, As Enzo has mentioned something broken,, often just a cracked solder joint.
Enzo's copyrighted thumping diagnostic approach comes highly recommended :lmao:
Give it a good thump with your fist,, does anything happen? Even a click or a change in the hum.
trust me it all can lead to a faster diagnosis of what is wrong. :tu:
Phil.