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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