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.

Any suggestions?

Thanks, Tom

wrote:

Any suggestions?

Sure - have 'em gone over by someone conscientious when something fails
instead of in a replacement/repair rush, to find out what the real
issue is. Cld even be a parasitic problem.

wrote

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.

Any suggestions?

If you fix it you should ensure that the fuse will blow before the
trannie in future! There is some chance that it can be fixed but if
not then a replacement is reasonably priced and available, so at
least you won't need two.

You must find out what the underlying problem is. Since it has
failed in the same way, it may not have been the fault of the output
transformer in the first place. Perhaps the guy who fixed it also
made some adjustment which has now wandered again.

Anyway, either you need to learn how to fix it yourself, or find
someone who cares about it enough to find out what it needs and do
the job properly.

If it sounds good it is worth fixing, and nearly all valve amps can
be made to run reliably. Nearly all require routine maintenance,
however, so you should arrange for this when you get it fixed, or
learn how to do it yourself.

Incidentally, lots of good stuff is made in China. They make rubbish
too...anything that sells, but you certainly can't assume that
poorly-made components are Chinese, or that Chinese components are
poorly made. They are not lacking in science and technology.

cheers, Ian