[Heathkit] Final Transistor replacement for Heathkit SB-104A

[Duane Gervasi]

To: John King K5PQW

From: Duane KF4ZS
Here is a copy of the listing from July 2006 regarding substitute Finals for the SB-104A.

I replaced mine with the recommended MRF- 450A and did not require any modifications.
I see RF Parts still lists them at $24.93 as MRF450A (note there is no DASH, MRF450A, if you do a search) here is the link.
http://www.rfparts.com/rftransistors/transistor-mrfsrfm/rftransistors-mrf-400.html?p=5


SB-104 A Final Transistor replacement MRF-450A





Message: 2
Date: Sat, 01 Jul 2006 15:41:49 -0500
From: JBA <uoba at bellsouth.net>
Subject: Re: [Heathkit] HW-104 finals
To: "KC8OPP Roger S." <kc8opp at yahoo.com>
Cc: heathkit at mailman.qth.net
Message-ID: <44A6DE0D.4060405 at bellsouth.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Roger!
I have used the MRF- 450A as well as the MRF-455A. Both work fine. I 
actually prefer the MRF-450A ($24.95 each at RF parts 1-19-2007, a little stouter than the originals and 
about $5.00 apiece cheaper that the MRF-455A ) . Solid 100-115 watts 
output across the bands. I've put them into seven or eight units with no 
problems. I currently have three SB-104/A here in the shack, all with 
the MRF-450A.
I used to try to follow Heath's advice and stay with matched sets only, 
but through the years I have found that it doesn't matter much about 
being matched. If the Beta numbers are anywhere close you should be fine.
The MRF-450A are also a direct replacement for the originals---no mods 
needed.
FYI------ I use the MRF-314A for the drivers. Never had a problem with 
them either. They're a little pricey, but I've never blown one.
Both are available at RF Parts.
My friend Kees Talen has an excellent site dealing with the 104's that 
includes among other things, a great schematic marked up with RF voltages.

http://www.qsl.net/k5bcq/sb104/sb104.html

Hope this helps,
Cheers!
Benton wb5twc