MG100

Hi

Heads up (sorry - awful pun!) if you hook an 8ohm with a 4ohm cab to the amp, the load is 2.6ohm. The amp is not designed for less than 4ohm. The more you turn up the volume, the more you are likely to damage the amp in this scenario.

The white glue your tech is talking about sounds like heat seal compound that you might (should!) see where the tab on the IC on power amp PCB attaches to the cooled heat sink unit. I'd epect to see some spillover. If he thinks its glue I'd wonder if he's experienced.

Stick a set of head-phones into the jack / run the FX send directly into the FX return of another amp - if this works fine the chances are the problem is with the power amp section.

I had a problem with my amp generating a terrible racket (and that wasn't just my playing...) that was fixed by replacing IC1 (TDA7273 - costs about €6. (I didn't have any problems with the fuse)

Whatever you find works please post an update so we learn

Hope it helps

Paul