[TenTec] 422 Centurion blowing fuses...

[Bob McGraw - K4TAX]

A secondary fuse for that transformer must be a HV fuse.  Thus should it 
blow, it must not explode or arc internally.  Your ordinary 3AG type fuse is 
not at all suitable for the secondary application.

Inrush circuit?    The original design was such that inrush current 
protection was inherent to the design.  Was something added by a previous 
owner?  Sounds as thought the amp had been sitting for years, perhaps not in 
a suitable environment.

I have had two different Centurion amps.  Always ran both to the max rated 
values with no issues.  Even with the AM mode.  Although lightning did eat 
one of them on the control board and QSK board area, there were no issues 
with the primary circuits.  The last amp was purchased new in 1991 and was 
sold fully operational and making rated power out only last year and with 
original tubes.  Care in tuning is the secret to success and longevity.

I find that many hams do not understand the correct tuning of a linear amp.

73
Bob, K4TAX






----- Original Message ----- 
From: "Bry Carling" <bcarling at cfl.rr.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Friday, January 31, 2014 1:08 PM
Subject: Re: [TenTec] 422 Centurion blowing fuses...


Thanks - I really appreciate the sage advice from you guys... it's a pity 
that the primary fuses
and inrush circuit didn't properly protect the transformer, but to be fair 
it is an old one. Serial
number is 11A10162. I wonder what year that signifies... I did notice that 
the core looks a bit
stained or maybe rusty?

This amp only lasted for a few weeks after buying it used.  You can be sure 
I will add a fuse
in the secondary after I repair it, and take a few other steps to better 
protect it. It seems
obvious that these transformers from TenTec are being run to their absolute 
limit in the
Centurion and should probably be derated a minimum of 10% in the future at 
this station. I
will not be running at more than about 800-900 watts output after this bad 
experience. I think
I will go the rewind route since the guys rewinding them has a great 
reputation, and will
probably create something better insulated and more reliable than the 
original.

I probably shouild have spent more and bought a new amp to begin with, but 
it's difficult to
spend the tens of thousands on ham gear that some guys are able to do...

Again many thanks to each person who shared comments and ideas.

Brian AF4K

On 31 Jan 2014 at 11:39, mcelmer1 wrote:

> I would keep it factory - the guys with the slide rules, pocket pens
> and
> letters after their names usually are qualified to design and/or the
> transformer.
>
> Mike
> W8TRN
> ----- Original Message ----- 
> From: "Mike Bryce" <prosolar at sssnet.com>
> To: "Brian Carling AF4K" <bcarling at cfl.rr.com>; "Discussion of
> Ten-Tec
> Equipment" <tentec at contesting.com>
> Sent: Friday, January 31, 2014 09:45
> Subject: Re: [TenTec] 422 Centurion blowing fuses...
>
>
> Brian, Bob, and the group,
>
> Let me pop in here with a bit of wisdom and a question
>
> was the $385 rewind from ten-tec or from another company?
>
> If if remember correctly, ten tec had some issues with their
> transformers
> used in some of the amps.
>
> If you have it rewound by a third party, you might end up with a
> better unit
> than a new one from the factory.
>
> Personally, an external high voltage power source always scares the
> snot out
> of me. It´d keep it factory and used either rebuilt or new.
>
> Mike Bryce wb8vge
> prosolar at sssnet.com
>
>
>
> On Jan 31, 2014, at 7:39 AM, Bry Carling <bcarling at cfl.rr.com>
> wrote:
>
> > Thanks so much Bob... The choices are rough - $500 plus shipping
> for a new
> > transformer
> > from Tentec or $385 plus shipping both ways for a rewind job!
> >
> > Yes, we get lightning, but this occurred when there was no
> lightning...
> >
> > Any thoughts or ideas are appreciated. I may have to go with an
> external
> > power supply...
> >
> > Brian AF4K
> >
> >
> > On 30 Jan 2014 at 22:05, Bob McGraw - K4TAX wrote:
> >
> >> Sorry to learn of the bad news.
> >>
> >> There are companies around that can rewind/rebuild that
> transformer.
> >> Certainly worth checking into as opposed to engineering some
> other
> >> transformer in its place.
> >> Per chance have you had a lightning strike lately?  That will
> do
> >> it.
> >>
> >> 73
> >> Bob, K4TAX
> >>
>
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