[R-390] Call For Information

[Bill Hawkins]

Here's another obscurity for the real 390:

There was a MWO to add a B+ fuse to the set. It lifted the transformer
center tap from ground in the PS module and brought it out to the
chassis using the wire for a + 28 VDC dynamotor supply. The dynamotor
wasn't used in the field because it was electrically noisy.

Then the +28 wire was clipped from the chassis power connector and
returned to ground through a fuse holder with a 3/8 A fuse.

What happened was that a modified PS module wouldn't work in an
unmodified receiver. Some radios were scrapped because they wouldn't
work, because of this modification. That's how I got my 390.

Bill Hawkins

P.S. There was also a thyratron DC/DC converter for 120 VDC supply,
but that one was also too noisy.