upgradde

Hello everyone. I bought, used, a Marshall MG100HDFX head and matching cab about 2 weeks ago. I had a gig last weekend and brought out my early nineties crate 4 x 12 extension cab to make her a full stack.

I had been playing it all week in practice with the master volume around 3. During sound check, it was making an awful, indiscernable chirping, screeching sound. After checking my connections, I changed my instrument cable and unplugged the footswitch, for some reason it worked fine for about 5 minutes.

I cranked it up to 5, played about 2 minutes of one song, and it blows and powers off. I could smell smoke, took her apart, fuse is fried. Keep in mind I know nothing about electronics. I put in another fuse, switched it on, blows it. I unplug everything, try another fuse, turn it on, blows it immediately and see some smoke come out of the fan unit.

I have since taken it to the local shop for repair.

I have a few questions perhaps you guys can answer. I researched this amp extensively after this happen and see this is a somewhat common problem with this model, is that true? Second, when the tech opened it, he asked me if I had done anything work on it prior, I said no and he said it looked as though someone's already been in there as the white glue on the fan was amateurly done.

Now I don't know if this amp is just flawed, or if perhaps I did something myself to it. The Crate extension 4 x 12 is only 4 Ohms. The Marshall is 8 Ohms, could this difference have blown the fuse like that? Is there a reason it would work at Master set to 3, but not 5?

I'm really lost here and sadly don't know much about electric.