[R-390] R 390A Work in Progress (Long)

[Craig C. Heaton]

Bill,

Have you checked or replaced C551? It's the 2uF oil filled cap in a large
metal can on top of the deck. Both of the two R-390/A that I've restored had
bad C551's.

Check this cap both for value and insulation resistance. If in doubt and you
want to replace it, you could mount a new one under the deck. I've got lots
of time and use a dremel tool with a cut-off wheel to open this cap on the
bottom. Cut along the soldered seam close to the edge, use a wood screw to
pull out the old foil & paper. I've seen two types of connection to the
rubber mounted solder posts. Some are crimped; these will have to be drilled
& tapped to add a screw and solder post. Another was real easy with holes
where the leads of the cap passed through to the outside and soldered.  A
NTE MLR205K630 fits inside perfectly, values are 2uF @630 volts.

73's
wd8kdg
Craig

Hi Group

I recently bought a Collins R390A that has or  had many issues but in great
physical
shape.

I recapped the IF module so far, AF & RF decks to go.  I seems to receive
well
however but overloads on moderate to strong signals......yes the AGC jumper
is
on the rear.  Reducing the RF gain corrects this overload,, all tubes tested
fine.

My question is this......I haven't aligned any modules or recapped the AF,RF
decks
could this be the problem?? I have tried turning the IF Gain lower.

I am unable to work with the IF in the radio (no  jigs).

Thanks

Bill  KB9IV