Hey man, mines unmodded, i have a hammond tube from an old hammond a100. Similiar to an NOS RCA. I use the cabnetulator output, because it takes some of the harshness out is all it really does. Its supposed to mimic the sound a 4x12 celestion being mic'd. It's the hughes and kettner "Redbox" inside the preamp. I switched the spring reverb to large hall lastnight at a gig and it took the harshness out of the tone and sounded wonderful.
That issue your talking about CMC, i had the same issue with my last one its the transformer and the bad part is it can't be fixed, or it would be pricey to fix since its a custom one for such a small preamp. Just let air flow get to it because i found it would drop the signal if it got to hot! I have mine on a rack tray with holes in it with 2 spaces above it so it has "breathing room" these little guys get hot.