[Hammarlund] SP-600 Chokes

[roy.morgan at nist.gov]

Quoting "Gary H. Harmon Jr." <gharmon at idworld.net>:

> I had a SP-600 that needs one maybe both of the octagon chokes.  One seems
> to have purged some if not all of its black yuck

Gary,

Lore from some years ago had it that some of the SP-600 chokes develop leakage
from the winding to the case. This increases the load on the B+ supply, the 5R4
and HV winding, but is not detectable otherwise unless you compare currents in
the choke output to the HV center tap at ground.

A "fix" published in Hollow State News called for mounting the choke on
insulators to "eliminate" the problem. Trouble is it creates a VERY DANGEROUS
situation for you and subsequent owners.  The thing becomes a somewhat lethal
source of unfused B+. DO NOT DO THIS "FIX".

Your radio may have this trouble because the one choke seems to have heated it's
potting tar to the gooey state.  To confirm, unbolt the thing, insulate it
temporarily from the chassis and measure for B+ on the case, or current from
case to chassis.

While you are at it, move the line connection to the primary tap on the
tranesformer from the 115 volt tap to the 125 (?) volt tap.  Your radio will
thank you.

Roy
K1LKY


Roy Morgan
7130 Panorama Dr.
Derwood MD 20855