[R-390] R-390A help

[Tim Shoppa]

"TChirhart" <sparks at codepoets.com> wrote:
> This is my first R-390A project. I have an Imperial 1963 vintage R-390A
> and the previous owner may have modified it. First of all, all 3 fuse
> holders are either missing or have been bypassed, the AC, B+ 1/8 amp and
> B+ ? amp have been bypassed with F-102 B+ ? amp fuse holder missing.. 

A couple of thoughts:

1. Verify that the original B+ wiring is still there and intact. Wire
colors and diagram are in the Y2K manual. Also look for charring etc.
on the wiring harness and check out the filter inductors (on the AF
deck) for continuity.

2. Verify that the wiring harness you have is one appropriate for B+
fuses. It is vaguely possible that someone transplanted a back panel
with fuseholders for B+ onto a chassis with a wiring harness that
didn't have B+ fuse connections.

> In the power supply, the 2x 26Z5?s are missing, the metal tube sockets
> crimped and a selenium rectifier installed over the sockets and the
> F-102 fuse holder is missing, apparently this is a modification. 

Is it vaguely possible that the "selenium rectifier installed over
the sockets" is an approx 200 ohm resistor (maybe with fins?) and
that there are diodes under the sockets?

> But why would you bypass the AC and 1/8 amp B+ fuse?

Original radios had no B+ fuses. But it makes no sense at all to
bypass the AC fuse.

Tim.