Is your ADA MT-100 (Microtube 100) only workin in one channel? Try this

[Dante]

As much as I hate to say this, it's a common problem with these amps. But, do not despair, it's an easy fix!

See this thread

Some cheap parts and some solder skills should put you back in the driver's seat (parts list below}

[Harley Hexxe]

Now if we could only figure out the cause and fix it, that would be great!

[Dante]

Yeah, if something else is FUBAR, maybe those transistors won't get fried. My question is; which two run channel B? I would only have to change two instead of four parts.

I guess that's another reason to change one part, and then check

[Harley Hexxe]

IF I'm not mistaken, as I was looking in the chassis at the four transistors, I think I traced the circuit from the B channel to the two on the right. This is as I'm looking at them with the three legs pointing towards me.
If I traced the circuit correctly that is. I'm nowhere near the level of MJMP.

[Dante]

so....the two closest to the rear of the unit?

[Harley Hexxe]

 

[MarshallJMP]

Here is the loadsing chart for the MT100, the power fet's for the B channel are Q106 and Q107 located on the bottom left of the PDF.

[Dante]

Thanks man!!
Correct me if I'm wrong, but does that mean the two closest to the FRONT of the unit? That's what it looks like
So, Q6 and Q7 are for channel A?

[MarshallJMP]

Not really sure, compare it with the pcb. But from what I can see the jacks are in the back so I "presume" that these are at the front. So double check it when the unit is open.

[Dante]

Yup - Nearest to the Front (I should have rotated this to match the PDF)
NOTE: you can see the Volume & Presence knobs at the bottom of the PDF (just noticed that)