wrote in message
oups.com...
About three years ago I bought a pair of Minnesota Audio Labs MAL 6550
tube mono blocks, about 10-12 years old and cost me $400 used. New they
cost $2400(from what I was told). Apparently they are fairly well
built, quality units which I can verify, that really do sound nice-when
working. Each amp uses 2 6550's and a 6an8. They worked very well for 2
years and then one of the output transformers went bad(Chinese
transformers?). The repair place replaced the output transformers on
the 2 amps with quality Hammond transformers, parts and labor $450.
They worked great for 6 months and then both amps started blowing
fuses, the big Buss KTK-1/4 $12 each type of fuse. One of the amps
started smoking from the new output tranformer before the fuse blew.
Took the bottom plate off and one of the wires from the transformer is
toast.


Worth fixing or is there possibly some design flaw that would make
these just a money pit. Seems that my old Dynaco's that I use as a back
up are way more reliable, but don't sound as good. I really don't want
to take these back to the same repair place, I don't trust them. But I
have another repair place to go to.

It sounds to me like they ARE Dynacos. That's the exact tube complement
used in the Dynaco 60 watt units. These are fixed bias circuits. It's
entirely possible that the output stage bias was improperly set (not set at
all.)

Norm Strong