B200s One channel phasing/flanging/cuting out then coming good again.

[rnolan]

I built a new rack recently MP-2, TC MOne (in MP-2 loop), B200s.  One B200s channel (channel B) looses volume and starts to phase/flange then cuts out.  After a while it starts to work again and then is ok, so seems heat related. 

I've completely re-flowed this amp in the past as I was getting very loud crackles and the fix (thanks MJMP) was re-flow around the power supply.  While I was doing that I just re-flowed the whole thing and it's been fine for a few years.  I haven't gigged with it as I bought a Carvin TS100 when the B200s was crackling and typically use the TS100 live, it's much newer and reliable, albeit much heavier. 

Any ideas what wrong? I'm guessing it's something to do with the phase inversion to feed the push/pull outputs transistors.

[MarshallJMP]

Are you sure it's the B200 and not the MP-2? When it does it switch the inputs, if the fault stays on the same channel, it's the B200, if not I would suspect the MP-2.