Do keep in mind that replacing 811's with 572's will only allow the amp to
perform to the limit of the power supply as designed for 811's. In practice
there is no advantage unless one desires to stress the power supply beyond
its design rating.
Yes, running the 572's at the lower voltage will greatly extend their life.
As to pushing the current higher on the 572's than the 811's to get more
output, one only has to wonder how long the power supply will last.
73
Bob, K4TAX
----- Original Message -----
From: "Rick NJ0IP / DJ0IP" <Rick@DJ0IP.de>
To: "'Rick Denney'" <rwd@iteris.com>; "'Discussion of Ten-Tec Equipment'"
<tentec@contesting.com>
Sent: Wednesday, November 07, 2007 8:36 PM
Subject: Re: [TenTec] Omni VI and non TT Amp
> Rick
>
> The better reliability of the 572's is not just a "perceived" improvement.
>
> The 572's have about twice the plate dissipation of the 811a's and they
> were
> designed to run at a much higher plate voltage. Running in place of the
> 811's at the lower voltage, the 572's should last forever, whereas the
> 811a's are prone to frequent popping under contest or heavy-use
> conditions.
>
> Most reports I've heard from people replacing the 811a's with 572b's in
> the
> Ten-Tec Centaur have been nothing but positive!
>
> 73
> Rick
>
> -----Original Message-----
> From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
> On Behalf Of Rick Denney
> Sent: Tuesday, November 06, 2007 11:07 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Omni VI and non TT Amp
>
> Ken Brown writes...
>
>> Last time I had an amplifier using anything like 811A tubes, they
>> were actually 572B, and it took two of them to get 650 to 800 watts
>> out. It was a Heath SB-200. Is that really an 811A?
>
> I was talking about the Ameritron AL-811a amplifier, which uses three
> 811a transmitting tubes, not the tube itself. The 572b tubes are
> indeed capable of greater output because of their higher plate
> dissipation rating, their greater grid current rating, and their
> higher plate voltage. Yes, the 572b is "like" an 811a tube, and some
> use them in amps designed for 811a tubes because of their perceived
> greater durability, but they aren't really the same.
>
> Rick, KR9D
>
> ---
> Richard W. Denney, Jr. PE|Iteris, Inc.
> Associate Vice President |107 Carpenter Dr. Ste 230 | 703.925.3819
> rwd@iteris.com |Sterling, VA 20164 |Fax 703.471.1757
>
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