[TenTec] Model 411 amp (aka Centaur)

k8mp at aol.com k8mp at aol.com
Thu Feb 4 17:55:50 EST 2016 

Yep, finding good tubes has been very frustrating. I just sent the new 811A's with the prematurely sagged plates back to DX Engineering. 
I have two, working, 40-plus-year-old Cetron 572B's that I pulled out of my SB-200 some years ago. My next (and probably last) try is those two tubes with a new Cinese 572B. It's an iffy proposition at best, but I'm tired of throwing money at the amp.


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-----Original Message-----
From: rick at dj0ip.de <Rick at DJ0IP.de>
To: 'Discussion of Ten-Tec Equipment' <tentec at contesting.com>
Sent: Thu, Feb 4, 2016 02:03 PM
Subject: Re: [TenTec] Model 411 amp (aka Centaur)


Al,

Unfortunately 2016 is not 1999.
It's tough to find good tubes anymore.

A few years ago, RF-Parts stopped the sales of 572B entirely until they
could work with their Chinese supplier and get the quality up to snuff.
They refused to sell an inferior product.

On their web site, RF-Parts writes "The Taylor Select 811A is the best
quality tube in current production." Obviously they mean best quality 811A.
The cost of a matched set of 3 is currently $95.85.

572B's are scarce.  They are available in very limited quantities with a
matched set of 3 costing $239.85.  More than twice the price of 811A.

It seems there is a waiting list.
See:  <a href="https://www.rfparts.com/572b-tubes" target="_blank">https://www.rfparts.com/572b-tubes</a> 

73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)



-----Original Message-----
From: TenTec [<a href="mailto:tentec-bounces at contesting.com?">mailto:tentec-bounces at contesting.com</a>] On Behalf Of Al Sirois
Sent: Thursday, February 04, 2016 6:53 PM
To: <a href="mailto:km2km at twc.com">km2km at twc.com</a>; <a href="mailto:tentec at contesting.com">tentec at contesting.com</a>
Cc: Ron Sirois; <a href="mailto:k8mp at aol.com">k8mp at aol.com</a>
Subject: Re: [TenTec] Model 411 amp (aka Centaur)

TUBES..........My T-T Manual says to use 811-A, not 572-B.....>

I bought matched tubes from RF Parts in 1999 and they are still in the amp

and working fine. I got 450 W out of them this morning on 80 meters.

I do have spare 572-B's, but they are for my back-up amp a FL-2100-B.

I've never swopped the tubes between the two amps..... I probably don't want
to.

Good Luck with you guys in this discussion group.

<a href="mailto:N1MHC at arrl.net">N1MHC at arrl.net</a>
Al Sirois
East Boothbay, ME 04544-0002
==========================

-----Original Message-----
From: Joe Papworth via TenTec
Sent: Thursday, January 28, 2016 9:54 AM
To: <a href="mailto:km2km at twc.com">km2km at twc.com</a> ; <a href="mailto:tentec at contesting.com">tentec at contesting.com</a>
Cc: <a href="mailto:k8mp at aol.com">k8mp at aol.com</a>
Subject: Re: [TenTec] Model 411 amp (aka Centaur)

Thanks Kris,
If I was desperate, I'd run it on two tubes.?
BTW- I haven't bit the bullet on a new tubes yet cuz from what I read on the
net, the ones on the market now just plain suck.


Seeeeeeeeeeeeya, Joe


-----Original Message-----
From: km2km <<a href="mailto:km2km at twc.com">km2km at twc.com</a>>
To: Discussion of Ten-Tec Equipment <<a href="mailto:tentec at contesting.com">tentec at contesting.com</a>>
Cc: k8mp <<a href="mailto:k8mp at aol.com">k8mp at aol.com</a>>
Sent: Thu, Jan 28, 2016 9:45 am
Subject: Re: [TenTec] Model 411 amp (aka Centaur)




Good morning Joe,

Yes, my AMP does make a "thunk" when turned on,  but, for example,  I have 
been
using it for an hour.  Then I turned it off.  Now, 15 minutes later, I turn 
it
on and it does not "Thunk".

I found that this AMP was built well, and the only issues for over 20 years 
have
been the tubes, and of of the toggle switches  (IP/EP).  The change to 10 
meters
was a snap.

Yes, it could have a quieter fan, but it is a good AMP and makes an S-unit
difference.

Good luck with the tubes.  BTW  I have used it with only two tubes, while
waiting for a new set.

Kris

Kris KM2KM
MERSCHROD
123 Warren Road
Ithaca, NY 14850

---- Joe Papworth via TenTec <<a href="mailto:tentec at contesting.com">tentec at contesting.com</a>> wrote:

=============
Hi Kris,
Thanks for the info.
It sounds like that store proprietor had gone a few rounds with some rigs. 
Hi hi
I'll try the tubes by adding one at a time tomorrow.
Say, does your Centaur make a loud in-rush clunk when you fire it up?
And where did you buy your matched set?

Later, Joe, K8MP


Sent from AOL Mobile Mail


-----Original Message----- 
From: km2km <<a href="mailto:km2km at twc.com">km2km at twc.com</a>>
To: Discussion of Ten-Tec Equipment <<a href="mailto:tentec at contesting.com">tentec at contesting.com</a>>
Sent: Tue, Jan 26, 2016 06:28 PM
Subject: Re: [TenTec] Model 411 amp (aka Centaur)


I'm late chiming in.   My problem with the fuses has always been a shorted 
tube.
You are on the right track.   Test one fuse at a time, or start with one, 
add
another, then the third.  BTW a matched set is better than an unmatched set
HOWEVER,  I had three misc tubes gathered over the years and put them in and

do
pretty well with them.  I did that while waiting for a new matched set.  Now

the
matched set is on the shelf waiting their turn!!!

The guy at the local electronics store said to me one day when I bought a 
dozen
fuses, "You do know that if you don't fix it then it will still blow fuses!"

good luck,

Kris


Kris KM2KM
MERSCHROD
123 Warren Road
Ithaca, NY 14850

---- Joe Papworth via TenTec <<a 
href='<a href="mailto:tentec at contesting.com">tentec at contesting.com</a>?'<a href="mailto:tentec at contesting.com" >tentec at contest?'="">mailto:tentec at contesting.com'>tentec at contest</a>
ing.com>
wrote:

=============
It has stayed on with the tubes removed for a while.?
I'm examining/ohming the tubes now.


-----Original Message----- 
From: Carl Moreschi <<a 
href='<a href="mailto:n4py3 at earthlink.net">n4py3 at earthlink.net</a>?'<a href="mailto:n4py3 at earthlink.net" >n4py3 at earthlink.ne?'="">mailto:n4py3 at earthlink.net'>n4py3 at earthlink.ne</a>
t>
To: wb5jnc <<a 
href='<a href="mailto:wb5jnc at centurytel.net">wb5jnc at centurytel.net</a>?'<a href="mailto:wb5jnc at centurytel.net" >wb5jnc at century?'="">mailto:wb5jnc at centurytel.net'>wb5jnc at century</a>
tel.net>;
Discussion of Ten-Tec Equipment <<a 
href='<a href="mailto:tentec at contesting.com">tentec at contesting.com</a>?'<a href="mailto:tentec at contesting.com" >tentec at contest?'="">mailto:tentec at contesting.com'>tentec at contest</a>
ing.com>
Sent: Tue, Jan 26, 2016 3:03 pm
Subject: Re: [TenTec] Model 411 amp (aka Centaur)




Don't overlook the possibility on an intermittent short in one of the 811's.

Carl Moreschi N4PY
58 Hogwood Rd
Louisburg, NC 27549
<a href="http: <a href="http://www.n4py.com" target="_blank">www.n4py.com</a>" target="_blank"><a href="http://www.n4py.com" target="_blank">www.n4py.com</a>

On 1/26/2016 2:54 PM, Al Gulseth wrote:
> Joe,
>
> Just an ohms check may not be enough. You may be dealing with an 
intermittent
> breakdown under high voltage. A "hi-pot" (high potential) test with an
> insulation tester etc. would be the only way to know for sure. A 
winding
> layer to adjacent layer partial short in the HV side could also account

for
> your symptoms, and might not be obvious because the winding resistance 
could
> show right at the low edge of the manufacturer's spec. (I went through 
that
> scenario years ago with a HV filter choke in a small AM BC 
transmitter.)
>
> 73 es GL, Al
>
> On Tue January 26 2016 11:28:03 am Joe Papworth via TenTec wrote:
>>     Thanks Andy. Was it the HV secondary that shorted?
>>
>>
>>    I isolated the HV secondary from the HV board and it reads open 
to the
>> frame and chassis. (Reads about 45 ohms when connected to the 
board)
>>
>>
>>    Thanks, Joe, K8MP
>>
>>
>>   -----Original Message-----
>>   From: P C Andy Anderson<<a 
href='<a href="mailto:xtraham58 at hotmail.com">xtraham58 at hotmail.com</a>?'<a href="mailto:xtraham58 at hotmail.com" >xtraham58 at hotm?'="">mailto:xtraham58 at hotmail.com'>xtraham58 at hotm</a>
ail.com>

>> To: Discussion of Ten-Tec Equipment<<a 
href='<a href="mailto:tentec at contesting.com">tentec at contesting.com</a>?'<a href="mailto:tentec at contesting.com" >tentec at contest?'="">mailto:tentec at contesting.com'>tentec at contest</a>
ing.com>

>> Sent: Tue, Jan 26, 2016 11:52 am
>>   Subject: Re: [TenTec] Model 411 amp (aka Centaur)
>>
>>
>>
>>
>>   Joe, I had a similar problem with my Centurion AMP.  It 
eventually failed
>>   completely. The secondary of the power transformer shorted to the

frame. I
>> had the Xformer rewound at TRS.  BTW this transformer problem is a 
known.
>>
>>   73' Andy, W3LI
>>
>>   ________________________________________
>>
>>
>>   Tuesday noontime, Joe:
>>
>>   I have a Centaur..............keep it covered when not in use.
>>
>>   My Elmer told me to always keep it covered..................dust 
is the
>>   problem.
>>
>>   Even when covered, open it up every two-three years and do a 
internal
>>   cleaning.
>>
>>   N1MHC/alsirois
>>   =============
>>
>>
>>
>> Gents,
>>
>>
>>   Have any of you gone a few rounds with a Centaur amp?
>>   I have a one that blows fuses very intermittently. It vaporizes 
them both,
>>   simultaneously, so it's apparently a dead-short somewhere. This 
happens
>> even in stand-by. (i.e. No key-down)
>>
>>
>>   Before I tear into it, anyone have any ideas of common failures 
in these
>>   amps?
>>
>>
>>   Later, Joe, K8MP
>>
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