Guitar Amp Repair
A collection of guitar amps that I have repaired.
Repairs:
- Marshall MG100DFX 100w
Article Date: 5/25/2024
Marshall digital FX combo amp.
Worked on this last year. This was an amp that had no sound. You should always check the basic stuff first like the speaker wiring, speaker, etc. The basic stuff checked out on this one.
After researching found there could be a number of other reasons for no sound on this model.
It could either be a blown fuse.
The fuse is located at the F1 on the circuit board (kind of lower center of the picture).
Or one of the resistors, one of the legs would sometimes burn off or come unsoldered and would stop working.
The larger flat black colored one in the picture (lower right).
Or possibly a certain 6.8V zener diode (D14)
could go bad forcing the amp into "mute" mode.
In this case the amp output chip had gone bad.
The larger chip with the 15 legs on the left side of the above picture here.
You can also see the amp output module conected to the heat sink and plugged into the main board in the flat black resistor picture above.
Used to be able to purchase the complete output module which would be great = plug and play. Can't do that anymore unless you're lucky enough to find one.
Even contacted Marshall directly, they do not produce that module anymore. So you have to carefully replace the TDA7293v chip itself, 15 legs to unsolder and then solder the new chip in place.
It can be done, this was a success.
This amp has since transformed into something different. It now looks like this.
