The most significant differences between an 811A and a 572B are that the 572B
has a higher plate voltage rating and higher plate dissipation.
If installed into an amplifier with the allowed higher plate voltage available,
the 572B will produce almost twice the output power of an 811A operating at its
specified plate voltage.
A 572B can replace an 811A in most amps but an 811A cannot replace a 572B
unless plate voltage is reduced or very bad things will happen.
In some cases, replacement of 811A tubes with 572B tubes can result in
parasitic oscillations and one may need to improve the parasitic suppressors in
this case.
This would be true generally only with older amps that did not have very good
suppressors.
It is true that, generally, a 572B will take more abuse than an 811A, but why
run any amp to the point at which tube damage occurs? The half dB you might
would not be heard by the listener.
Tuning should be done at reduced power anyway. If you improperly tune a 572B
tube at full power, you will only destroy a more expensive tube than the cheap
811A tube.
Gary
W0DVN
> On Feb 5, 2016, at 9:09 AM, Paul Ceglia via TenTec <tentec@contesting.com>
> wrote:
>
>
> THE DIFFERENCE BETWEEN 811A'S AND THE 572B IS THE 572B CAN TAKE MORE ABUSE
> IN THE CASE OF MISTUNE AND ARE MORE HEAVY DUTY .
>
> IT IS MY UNDERSTANDING YOU GET NO MORE POWER .THAN THE 811A, HERE IS
> THE LINK TO RF PARTS ONE LINK IS THE INFO ON ORDERING AND THE OTHER LINK IS
> THE HISTORY OF THE 572B I WILL ONLY BUY FROM RF PARTS THERE SERVICE AND
> WARRANTY ARE STELLER THANKS PAUL N3TMX
> https://www.rfparts.com/572b-tubes
>
> https://www.rfparts.com/index.php/fileuploader/download/download/?d=0&file=custom%2Fupload%2FFile-1417561155.pdf
>
> -----Original Message-----
> From: Carl Moreschi <n4py3@earthlink.net>
> To: tentec <tentec@contesting.com>
> Sent: Thu, Feb 4, 2016 1:07 pm
> Subject: Re: [TenTec] Model 411 amp (aka Centaur)
>
> The 57B's are superior to 811's. When I had my Centaur, Paul Clinton at
> Tentec advised me to make the switch. That worked out very well.
>
> Carl Moreschi N4PY
> 58 Hogwood Rd
> Louisburg, NC 27549
> www.n4py.com
>
> On 2/4/2016 12:52 PM, Al Sirois wrote:
>> 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.
>>
>> N1MHC@arrl.net
>> Al Sirois
>> East Boothbay, ME 04544-0002
>> ==========================
>>
>> -----Original Message----- From: Joe Papworth via TenTec
>> Sent: Thursday, January 28, 2016 9:54 AM
>> To: km2km@twc.com ; tentec@contesting.com
>> Cc: k8mp@aol.com
>> 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 <km2km@twc.com>
>> To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
>> Cc: k8mp <k8mp@aol.com>
>> 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 <tentec@contesting.com> 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 <km2km@twc.com>
>> To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
>> 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='tentec@contesting.com?'mailto:tentec@contesting.com'>tentec@contesting.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='n4py3@earthlink.net?'mailto:n4py3@earthlink.net'>n4py3@earthlink.net>
>>
>> To: wb5jnc <<a
>> href='wb5jnc@centurytel.net?'mailto:wb5jnc@centurytel.net'>wb5jnc@centurytel.net>;
>>
>> Discussion of Ten-Tec Equipment <<a
>> href='tentec@contesting.com?'mailto:tentec@contesting.com'>tentec@contesting.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: www.n4py.com" target="_blank">www.n4py.com
>>
>> 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='xtraham58@hotmail.com?'mailto:xtraham58@hotmail.com'>xtraham58@hotmail.com>
>>
>>
>> >> To: Discussion of Ten-Tec Equipment<<a
>> href='tentec@contesting.com?'mailto:tentec@contesting.com'>tentec@contesting.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
>> >>
>> >> _______________________________________________
>> >> TenTec mailing list
>> >> <a
>> href='TenTec@contesting.com?'mailto:tentec@contesting.com'>TenTec@contesting.com
>>
>> >> <a href="http: lists.contesting.com="" mailman=""
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>> target="_blank">http://lists.contesting.com/mailman/listinfo/tentec
>> >>
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>>
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>> target="_blank">http://lists.contesting.com/mailman/listinfo/tentec
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>>
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>> target="_blank">http://lists.contesting.com/mailman/listinfo/tentec
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> _______________________________________________
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>>
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>> target="_blank">http://lists.contesting.com/mailman/listinfo/tentec
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>>
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