I discovered I've sold all my extra filter chokes. Hopefully I can find one. The parts list says "13 h at 100 ma." The one installed is 8 h at 85 ma and 250 ohm dc resistance. Original mounting holes 3 1/8" (3.125") apart.
The bad choke:
Possible replacement parts:
Hammond 159P 10 h 125 ma 3.56 mounting
Hammond 159M 15 h 100 ma 3.56 mounting
I removed the choke and tested again, it matches what it says on the label. Confusing. Still wrong part though.
My starting point for this part of the job... I found it easier to make notes on a picture than to tag the wires.
The great knotted thing on the right is power cord. It was dry-rotted. The fuse holder takes a
1
One thing to note: This radio has a very early version of the power transformer.
Here are some screen grabs from the web:
While doing this, I note that in the black & white image (left), the date of 1944 appears on the stamp and the tuning cap cover is the
later version (SX-28A) with the top cover clips. This sort of contradicts 'early version'.
I added a Thermistor (NTC 10D-1, 3 amp, 10 ohm) in series with the white AC power lead. I replaced the two 0.01 caps
from power transformer primary connections to ground. I replaced the power cord.
My new cord is only a few inches long. I don't
like arguing with a long cord while I'm working with the radio. If I want to power it up, I add an extension cord.
(Doesn't look like it but it is a grounded plug.)
When I got the radio - the speaker terminals, all three of them, all different styles, one
missing the knob - were mounted on a piece of broken plexiglass. I didn't even bother taking a
picture. I replaced the mess with two modern banana plug jacks as shown. They fit in the holes perfectly.
No rectifier tube, meter on one half of high voltage winding, 2 amp fuse. Turn on Tone Contol knob, measure 339 volts on each half of the secondary. Meter only does 600 volts. Fuse didn't blow.
Next step: find a choke.
Page: /5th_radio_resurrection/Power_supply/Resurrect_power_supply.shtml
Last modified: Thursday, 23 Apr 2026