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?

Hello,

Can anyone help diagnose a Yamaha B100-115III bass amp? Here are a few pictures of the amp. The third shows a resistor that appears to be burnt (doesn't show up in the pic well). I also have a service manual with a schematic. I'm not experienced with electronic repair, so any help getting this amp working again would be greatly appreciated.