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Re: [Amps] Replacing 3-500Z tubes with 4-400A tubes

To: "donroden@hiwaay.net" <donroden@hiwaay.net>, "amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] Replacing 3-500Z tubes with 4-400A tubes
From: Glen Zook <gzook@yahoo.com>
Reply-to: Glen Zook <gzook@yahoo.com>
Date: Fri, 9 Dec 2011 07:42:29 -0800 (PST)
List-post: <amps@contesting.com">mailto:amps@contesting.com>
How are you going to use an SB-200 as a "tube checker"?  The 572B tubes used in 
the SB-200 are 4-pin "medium" and the 4-400A and 3-500Z tubes use a 5-pin 
"large"!  Then there is problem of the filament voltage.  The 572B has a 6.3 
VAC filament and the 4-400A and 3-500Z have a 5.0 VAC filament!
 
Glen, K9STH


Website:  http://k9sth.com


________________________________
 From: "donroden@hiwaay.net" <donroden@hiwaay.net>
To: amps@contesting.com 
Sent: Thursday, December 8, 2011 4:26 PM
Subject: Re: [Amps] Replacing 3-500Z tubes with 4-400A tubes
 
4-400s will work in an SB 200 , but you cant slide it back in its case.

( tube checker only !!!  HV EXPOSED !!  )

Don W4DNR



Quoting Bill Fuqua <wlfuqu00@uky.edu>:

> Well, it does blow some air on the socket but not up thru the socket to the
> seals.
> In some 4-400A tubes the pins are connected by smaller conductors from the
> socket and
> do not themselves conduct a lot of heat.  That is why the sockets and tubes
> have holes
> in them and the shields as well. The air is supposed to blow up thru the
> holes and hit the
> seals and then out the sides holes in the metal shield.
>    The 3-500z tube do not have the metal shield and the side flow does hit
> the seals and
> along with the pin cooling they stay cool enough.
>    You may get by anyway with the 4-400As because  they will be running at
> lower power and
> they are running in either CW or SSB modes. But if you were running full
> bore RTTY you
> may have a problem.
>    The tubes were designed to run with the plates red 24/7 and which is
> unlikely in
> a SB220. This is why I was wondering if someone had some real experience.
>     A very interesting seal cooling mechanism is the one that was used in
> the EIMAC
> 1000T.  The tube was the same size as a 450TH but lots more power. They
> provided small
> metal tubes that carried low pressure air straight to the seals on the base
> and the grid.
> I guess they were intended to be used as a upgrade for 450T transmitters
> using same sockets
> and physical size.
>
> 73
> Bill wa4lav
> At 04:32 PM 12/6/2011 -0500, Carl wrote:
>> The SB-220 cools the filament pins.
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message -----
>> From: "Bill Fuqua" <wlfuqu00@uky.edu>
>> To: "John King" <k5pgw@yahoo.com>; <amps@contesting.com>
>> Sent: Tuesday, December 06, 2011 9:15 AM
>> Subject: Re: [Amps] Replacing 3-500Z tubes with 4-400A tubes
>>
>>
>> >  One possible issue with the 4-400A is that it has a metal shield around
>> > the glass seals on the base.
>> > The cross flow cooling used in some amplifiers does not work well and an
>> > additional fan
>> > may be need to cool the seals.
>> >   Maybe someone can comment on this that have had personal experience
>> > making the conversion.
>> > 73
>> > Bill wa4lav
>> >
>> >
>> >
>> > At 04:20 PM 12/4/2011 -0500, John King wrote:
>> >>I have several very good 4-400 A tubes and have replaced a pair of bad
>> >>3-500Z tubes with a pair of 4-400A tubes in a Heath SB 220 amp.
>> >>
>> >>I have noticed much lower resting current being drawn when keyed up. I
>> >>have noticed about 200 watts less power output with 100 watts drive. The
>> >>4-400A tubes are as new.
>> >>
>> >>I made no changes to bias or other parameter adjustment. I would
>> >>appreciate the benefit of your knowledge and experience regarding the tube
>> >>substitution. Thanks and 73, John, K5PGW
>> >>_______________________________________________
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>> >
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>> >
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>
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