Was there anything that preceded it not working? Like a pop or hiss? Check the effects loop switch on the back of the amp. If it's engaged and nothing is connected, you won't get signal from the preamp to the power amp. Failing that, (and if you are comfortable doing so) you can drop the head out an...

For the pop when switching channels, unplug the foot switch and see if the channel button on the amp still generates the pop. If only the foot switch pops, there's yer problem. :bgrin On the other hand, if the button on the amp causes the pop as well, then try disconnecting the reverb tank. In my ca...

Yep. Sounds like you have a bad tube. The plate is glowing brighter because it's drawing too much current, which blew the fuse (the flash and the pop). Assuming it's a used amp: Replace the power tubes, replace the fuse and re-bias. Then you can get back to rockin'. :jam EDIT - If you plan to do it ...

Did you buy it new or used? If it's new, take it back as it's under warranty. If it's used (not under warranty) and you are not comfortable opening up the amp and trying to fix it yourself, then take it to a tech to have it checked. Just a guess, but it sounds like a power tube let go and smoked an ...

To echo what Lizzy said, the MA100H and MA100C have 4 power tubes. So the test points on the amp are each measuring 2 tubes. Per tube it should be 38mV, so the measurement for 2 tubes is 76mV. An observation from my own experience; when one of my original tubes died (MA100C), I playing around with d...

As long as you match the impedance by having the speakers plugged into the correct jack, it will not make a difference on the bias setting.

In the schematic, C5 is the cap in the clean volume path. So based on that, it's definitely the treble bypass cap (a.k.a. the bright cap). It's most likely soldered to the pot between hot lug and wiper lug. Like Surf said, you could always swap it out for a 47pF and if it doesn't have the desired re...

The power tubes are Winged C EL34's and the preamps are Shuguang 12AX7's. At least that's what they were in my MA100C. The only difference should be that the 100C has 4 power tubes vs. the 2 in the MA50C.

Like SteveD said, they are just branded Marshall.

I'm new to the forums. I'm the proud owner of a MA100C since Dec 2010 and it seems everytime I look for info on this amp, my search brings me back here. So I finally decided to register. The MA series gets bashed pretty hard in a lot of forums and other places...mostly by people who have only played...