-> What do you consider proffesional use?  I play mine between 5 and 6
-> hours straight every Saturday at volumes enough to get over a too
-> loud inept drummer. Been doing this for a while now, close to a year.
-> I haven't had any problems and seriously hope I don't.  Have you
-> heard anything about substituting a beefier transformer?
I have heard that they don't stand up to touring very well.  Remember
that in a very big hall, you have to really crank the amp most of the
way up.  After being run very hard for a few hours, then they are moved
while they are still warm and take a lot of bumps and jolts when they
are the most succeptible to damage.  The newer amps from all
manufacturers are this way and it's a problem for the professional user.
Anyway, my comments on the 900 output transformer don't come from
personal experience, just what I hear.  If you look at a Mojo or other
catalogs, the 800 and earlier transformers are substantially more money.
The 900's are considerable less.
I also looked at the Guitar Center "NOS" 800's.  One was sitting on top
of a 900 and you could compare the transformers.  There *is* a
considerable difference in the size, and they do have a rep for blowing
up under hard use.
As far as beefing it up, I don't know if that could be done or not. I
know that voltages must be met and maybe Rich or Jeff V could tell you
better than I could.
I do know that if yours has given you no trouble this far, I wouldn't
worry about it at all.  Even it it does happen to go, they aren't too
expensive to replace.  Hell, the Fender Blues series amps have a
horrible rep as well, and I'd buy one if I needed one.  The breakdown
ratio to units actually produced and sold are probably in the
.000000 percentage.  It's just the troublesome ones we hear about. So
bear that in mind.  Also, how many 900's are out there in the world?
I bet it's a helluva lot :)))
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