[TenTec] Centurion Amp Woes

[Duane Calvin]

My Centurion, vintage ~1998, ran flawlessly after (1) an early life (~1 hr
operation) fail of the bias transistor - I replaced with TT help, and (2) at
~ 3 years of age one of the 3-500ZG's failed with the common grid/cathode
short.  Otherwise, it put in many hours of operation without issues.

This tells you nothing about the current run of Centurions.  TT was making
their own transformers when I bought mine - don't even know if that's still
true.

	73, Duane
	

Duane Calvin, AC5AA
Austin, Texas
www.ac5aa.com 
 
-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Charles Delaune
Sent: Sunday, October 08, 2006 10:42 AM
To: TenTec at contesting.com
Subject: [TenTec] Centurion Amp Woes

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