MT200 Low Output

[GuitarJesus]

I finally got my MP-1 today and hooking it up to my rack, it has almost no output, and sounds fizzy as all hell.  I have the controls dimed all the way, try channels independently, also in bridged mode, and its just low.  like maybe what would be a 1 watt amp set at 1.  The protect mode doesn't light up after the initial warmup, the tubes seem fine, and I also put new JJ's in it and all is well with the tubes. 

Fuses are all good, so I can't think of where to start inside this thing. 

Any suggestions?

[rnolan]

Hey Jeff, so first step is to isolate the issue.  Do you know you have decent output from the new MP-1?  e.g. plug it into your micro cab into PC? (or headphone out into either headphones or into PC line in)   Has the MT200 worked before ?  Try a different line level signal into it e.g. mini jack from you phone > 2 x 1/4" jacks > MT200 > cabs.  Are all the leads known to be good?  Are you using proper speaker cables (not guitar input cables) to the speakers?  Do you know the speakers work?  Alternately, if you are running the MT200 into the Microcab and not speakers, the Microcab my be the culprit (are all it's settings correct?).

If the issue is the MT200 (and it may well be if it's never worked for you before?) it may be the output FETS (Field Effect Transistors), possibly damaged by someone using bridge mode incorrectly  .  It's unusual for both channels to be damaged, IIRC past issues tend to be one channel not working because of blown FETS but that seemed to be the most common MT200 problem (aside from protect mode issues). 

If I understand correctly, you've bought a bunch of gear (Microcab, MT200, Digitizer 4 and now MP-1) but have never been able to use it all together until now that you've got the MP-1.  So you need to check each unit separately to ensure they work correctly, any of them could be the issue except maybe the Digitizer 4 (although if it's in the MP-1 loop and the loop is "In" and it's not working correctly it could part of the issue, easy to isolate though, just turn loop off). 

You also have other amps (that you know work) so test MP-1 and digitizer 4 with them.  When you are sure it's the MT200 (or if you are sure already) then it's time for tests for it. 

For me, that you get some sound but it's supper low and fizzy, would indicate either something in the chain isn't working properly (either leads or another unit), but if you know they all work, then my guess would be the MT200 output FETS.

[GuitarJesus]

Hey Jeff, so first step is to isolate the issue.  Do you know you have decent output from the new MP-1?  e.g. plug it into your micro cab into PC?

So here is how I trouble shooter to make sure it wasn't my other gear.

1. Plugged MP-1 into my Super Reverb.  All is good.
2. Plugged headphones into MP-1, all is good.
3.  Plugged directly into Digitizer which then went to my Super Reverb, all was good (other than it may not be the piece for me and I might unload it).
4.  Microcab was never in the signal chain as I don't have my PC setup for recording yet.
5. Plugged my Super Reverb speaker out to my Marshall 4x12 that the MT200 was plugged into.  It worked fine despite only doing it for 10 seconds since the SR runs at only 2 ohms and the cab is 16.

So the issue is definitely the MT200. 

[Harley Hexxe]

Super Reverb runs at 4 Ohms. 16 Ohm speakers won't hurt it, but 2 Ohm speakers will. Never run a speaker load below the niminal impedance of your amp. That will cook your output transformer.

[GuitarJesus]

A Blackface SR has four 8ohm speakers wired in parallel.  That works out to 2ohms.  Crazy, I know but it's true.