[Heathkit] SB-401 Final Question (was HW 101 Final Question)

[Glen Zook]

Replacing the 10 ohm resistors is pretty much a "must
do" on the HW-100, HW-101, SB-100, SB-101, SB-102,
SB-110, SB-110A, SB-400, and SB-401.  In the Collins
32S-1, 32S-2, 32S-3, 32S-3A, KWM-2, and KWM-2A there
are 12 ohm resistors used for the same purpose.  Those
need changed as well.

Another thing is tighten all of the machine screws and
nuts that go through the chassis (especially those
that hold the circuit boards in place).  All of the
grounds in the units are made through these and they
definitely work loose over the years.

The various elecytrolytic capacitors in the unit are
suspect and replacements from places like Mouser are
pretty cheap.  I would consider replacing those.

The potentiometers in the SSB balanced modulator often
go bad.  Replace these with multi-turn potentiometers
for ease in nulling the carrier.

Other than that I cannot think (at least "off hand")
other things that might cause problems.

Glen, K9STH


--- Chris Kepus <ckepus at comcast.net> wrote:

I picked up a nice looking SB-401 that will soon be on
the bench.  After reading your comments about the
HW-101 10 ohm resistors, I looked at the schematic.
Sure enough, there were the 10 ohm resistors that you
recommended replacing in the HW-101.  Same
recommendation for the SB-401??
 
Also, are there any other "don't ask, just do it(s)"
with respect to the SB-401 restification when it's on
the operating table?









Glen, K9STH

Website:  http://k9sth.com