[Heathkit] Power Transformer Ratings

[Tom Chesek]

I checked my copy of the SB-401 and it uses a 54-198 power transformer which 
has a tapped filament and tapped bias section.  The main B+ has no tap.  I 
do not have the SB-400 manual to check but my 2 copies of Heathkit 
transformer cross reference show the 54-179 being used in the HW-16, SB-400 
and SB-401 and the 54-198 (dual primary input) for the SB-401 only.

Tom K3TVC


-----Original Message----- 
From: Michael D. Harmon
Sent: Friday, August 15, 2014 11:35
To: Heathkit at mailman.qth.net
Subject: [Heathkit] Power Transformer Ratings

Hi Andrew,

I don't have the exact specs for the transformer - most of the time
Heathkit had their transformers custom made for them, so you probably
won't find an exact match from Stancor, Triad, UTC, etc.

I can tell you that the same transformer is used in both the SB-400 and
SB-401 SSB transmitters.  I looked at the HW-16 schematic and added up
the filament currents.  The 6.3V winding supplies 5.25A to the HW-16
filaments, so it's good for 5-6A.  The bias winding supplies around
-130V when used with a half-wave rectifier.  The B+ winding supplies
700V to the PA, plus the B+ voltage to all the other tubes.  The PA
draws around 220mA when loaded up, plus probably another 75-100mA for
the other tubes in the unit.  I's guess that the transformer can provide
700V at 250-300mA when used with a voltage doubler arrangement.  If you
are building a home-brew transmitter, you should be able to get enough
out of the transformer to run 75-100 watts.  Just bear in mind that CW
and SSB service is ICAS, NOT CCS!  Don't try to use the transformer at
these ratings in AM, FM or RTTY service!

Hope this helps.
Mike, WB0LDJ