[TenTec] RE: Centurion Amp Woes

[Dan Atchison]

You are not alone.  The HV power transformers in the Centurion are a piece
of crap, IMHO.  Why?  I personally have lost two HV transformers, both for
shorted primaries (high resistance between the two 115V primaries).  This is
a known problem and nothing has been do about it.  My first transformer let
loose after 18 months.  I tried to get them to replace it under warranty
since I've read of this happening to many people.  They would not.  To boot,
I sent in my perfectly working 3-500ZG with the amp and they told me one was
defective (although it is quite possible it was damaged in shipment -- BUT
if the transformer didn't let loose I wouldn't have had to send it back,
would I?). 

Eight (8) months after the first HV transformer was replaced, the second one
failed exactly the same - high resistance short between the two primaries.
After having no luck with TenTec replacing the first under warranty (even
tho it was out of warranty, I realize, but it's been an ongoing problem for
them), I bit the bullet and ordered a Peter Dahl replacement.  Yes, TenTec
would have replaced it under warranty but I didn't want another piece of
crap.  The Peter Dahl transformer is the same size, drops right in, and I
had them put a few extra windings on the secondary to give 2400VAC vs.
TenTec's 2250VAC or so.  Haven't had a problem since.

TenTec needs to come clean on this and fix their problem with their vendor.
This is silly.  Since I got my amp 3 years ago, I've spent another $1K
getting it fixed.  Am I upset?  You bet.  The Centurion is a fine amp, but
their HV transformers are crap. Did I say their HV transformers were a piece
of crap? 

I have a spare, TenTec HV transformer with shorted primaries if anyone wants
one.

Next time I'll tell you what I really feel about the Centurion HV
transformer.

Dan -- N3ND

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I'm having an on going problem with my NEW Centurion. Several weeks ago the
line fuses blew for no apparent reason. The amp had been on for several
hours, but in Standby mode. All of a sudden the amp bit the dust as both
line fuses blew. The line voltage is 240v and checked O.K. The tubes
checked-out O.K., as well. That is to say, no shorts between elements
(checked with ohmmeter) or plate arcing (removed tubes and replaced line
fuses then turned amp back on - fuses blew, again). After I made these
initial checks I sent the amp back for repair. It was repaired then returned
with the following list of items which were replaced:

Relay and cover (relay contacts were welded)
Q1 (transistor from HV-AC board)
Rectifiers (looks like all of them) in HV rectifier board 
Power Transformer (Hi impedance short)

I've never heard of a Hi impedance short, by the way! In electronics school
I was taught that a short, if anything, is zero or near zero resistance.
Anyway, it looks as if the power transformer was defective and took all
those other components with it when it bit the dust!

Since the amp was repaired (about two weeks ago), it has been operating
flawlessly. Then, last night, after making a few contacts and being on for
approximately six hours the line fuses blew AGAIN!!! The fuses blew about
two hours after I had made my last QSO on 40 meters with the amp. Like
before, the amp was on but not being used. Then, out of nowhere the line
fuses blew. I'm going to assume that, once again, I have a defective power
transformer! Looks like, Monday morning, I'll be on the phone, once again,
with Ten Tec! It's a shame because when the damn thing is working it's one
of the finest amplifiers I've ever operated, but I'm getting close to the
point where I'm ready to tell them to either replace the amp or refund my
$$$! 

My question is...have any of you other Centurion owners experienced this
problem? Is there a power transformer issue with the Centurion. In other
words...is it possible that there was a run of defective power transformers
that "fell through the cracks", sort of speak? I understand Ten Tec builds
their own power transformers for the Centurion. If there is an "issue" with
those transformers I feel the problem will only happen again if the
transformer is replaced or I opt for a new Centurion. 

Charlie - N5BLY