[TenTec] 1999 Centurion amplifier - grid goes negative/output goes to zero

[Frank Kirschner]

Same here.  I bought a matched pair, replaced both tubes, and it has worked
FB since then.

73,
Frank
KF6E

On Fri, Mar 9, 2018 at 4:07 PM, P.C. Anderson <xtraham58 at hotmail.com> wrote:

> I had one bad tube in my Centurion that caused that condition.
>
>
> Andy...W3LI
>
>
> ________________________________
>
>
> Don't do that for a long time. The output matching network is designed for
> the plate impedance of two tubes in parallel, which is one half the
> impedance of only one tube. The variable capacitors in the Pi network
> probably have enough adjustment range to work at either impedance on the
> higher bands, but maybe not on the lower bands.
>
> DE N6KB
>
> On Fri, Mar 9, 2018 at 8:58 AM, Mike Schatzberg <
> cherokeehillfarm at earthlink.net> wrote:
>
> > You can remove one tube, greatly reduce drive, and see if there is any
> > output. Make sure the anode cap from the removed tube is clear of
> > everything near it and not shorted. Replace all safety screening.
> >
> > You can test both tubes, one at a time.
> >
> > 73,
> >
> > Mike
> > W2AJI
> >
> > Sent from my iPhone
> >
> > > On Mar 9, 2018, at 12:48 PM, Stan Gammons <s_gammons at charter.net>
> wrote:
> > >
> > > Sounds like one of tubes shorted. If they are still under warranty, I'd
> > contact RF Parts and see what they say.  They replaced a tube I had that
> > shorted.
> > >
> > >
> > > 73
> > >
> > > Stan
> > > KM4HQE
> > >
> > >
> > >> On March 9, 2018 11:11:45 AM CST, Bob  <w3hkk at roadrunner.com> wrote:
> > >> Bought this  used  from an estate sale in 2014.  Worked great for 3
> > >> yrs. Then a tube short blew a fuse.  Replaced both finals  and all was
> > >> well until a few months ago. The  amp  worked well for a few
> > >> transmissions, then the output went to zero.  After a few  cycles of
> > >> this I noticed the grid current which rested at zero began to migrate
> > >> negative.  As it   got worse, the output dropped to nil.
> > >>
> > >> One suggestion was that one of my new tubes  ( from RF parts)   is
> > >> failing.  Another was  a possible problem in the AGC circuit.
> > >>
> > >> Other suggestions?  Also, I may need  a repair tech and don’t want to
> > >> ship the amp, so someone in Ohio or driving distance from central OH
> > >> would  be a plus.
> > >>
> > >> Thanks.
> > >>
> > >> Sent from Mail for Windows 10
> > >>
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