[Collins] 572B and the 30L1

[Robert & Linda McGraw (K4TAX)]

Around and around we go.  For the life of me I can not find any true or 
sound advantage to replacing the 811's in the 30L-1 with 572B's.

Let me say that Glen is absolutely correct as well as those statements by 
Jerry regarding the correct tube configuration for the 30L-1.  Be sure the 
plate orientation is correct or likely failure will occur.

The way I see it, quality 811's suitable for use laying on their side are 
available for reasonable prices.  The 572B's are also readily available but 
for somewhat higher prices.  The output of the 30L-1 amp is no greater with 
572B's nor is the IM improved when utilizing the 572B's.  As to longevity, 
the 811's in my amp are 40 years old and have 1000's of hours of usage. 
Should I replace them with new 811's then I'd expect them to last another 40 
years at which time I'll be 105 years old and perhaps a SK long before that. 
I can't take the amp with me so again, I find no advantage.

Now as to using the 572B's in the SB-200, it was designed to use 572B's. 
That's a given and a must for that amp.   The 30L-1 was designed to use 
811's.   In this case comparison of amps,  "A" does not equal "B" nor does 
"B" equal "A".  While the plate dissipation of the 572B is greater than the 
811 there is nothing to be gained by this fact.  The input power vs. output 
power of the 30L-1  is the same regardless of which tube is used.  Thus the 
added plate dissipation capability of the 572B factually provides no 
advantage.   As to 572's running cooler, I don't see this as being correct 
as plate dissipation result is heat.  My physics book says that 50 watts of 
dissipation  from one tube is equal in heat the 50 watts of dissipation from 
a different tube.  Roughly, input power minus output power equals 
dissipation.

The only thing I can find to be gained by using 572B's in the 30L-1 is the 
basic inflation of ones ego.  Perhaps that's worth the aggravation in 
changing tube types and the dollars to obtain them.

73
Bob, K4TAX

----- Original Message ----- 
From: "Glen Zook" <gzook at yahoo.com>
To: "Frank" <frank at k5dkz.com>; "Glen Zook" <k9sth at sbcglobal.net>
Cc: <collins at mailman.qth.net>
Sent: Friday, March 30, 2007 10:10 AM
Subject: Re: [Collins] 572B and the 30L1


> The original post was about replacing the 811A tubes
> in the 30L-1 with 572B tubes.  My original reply was
> to be careful when using the Chinese manufactured 572B
> tubes in linears like the Collins 30L-1 linear and
> Heath SB-200 that have them mounted horizontally
> because those particular tubes are notorious for being
> manufactured with the elements not in the same plane
> as the original U.S. manufactured tubes and that the
> elements tend to "sag" and short out.
>
> In the 30L-1 linear you won't get any more power
> output from 572B tubes than you will with the original
> 811A tubes because the power supply just cannot put
> out any more.  In the Heath SB-200 you will definitely
> get only about half of the power if you put in 811A
> tubes in place of the 572B tubes.  The major benefit
> of replacing the 811A tubes in the 30L-1 linear is
> much longer tube life.
>
> By the way, you do know that the 30L-1 linear was not
> the first equipment produced by Collins Radio Company
> with the model number 30L-1.  When the 75A4 came out
> Collins announced the 30L-1 SSB transmitter and ran
> full color advertisements in various amateur radio
> magazines, in the ARRL Amateur Radio Operator's
> Handbook, etc.  However, after the ad "blitz" Art
> Collins decided to change the model number to KWS-1.
> If you look closely at the early KWS-1 ads you will
> see that the unit pictured actually has 30L-1 on the
> front.
>
> Also, Collins advertised the 32W-1 SSB exciter at the
> same time.  The 32W-1 was the 30L-1 (KWS-1) without
> the linear amplifier.
>
> Glen, K9STH
>
>
> --- Frank <frank at k5dkz.com> wrote:
> Have you considered using 811s?
>
> They are cheaper, run cooler, fit better, and you get
> just about the same power out.
>
>
>
>
>
>
>
>
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
>
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