Speaking of which, does anyone have first hand knowledge of loosing a
mechanical filter due to a leaky or shorted C553? I know Henry Rogers mentions
having some bad R-390A mechanical filters but the failure was on the grid side
of the filter, not the plate side. I think that it has more to do with the
reliability of those early mechanical filters then to a leaky C553.
I have repaired a few of the mechanical filters used in the R-390A. The
problem is usually a broken transducer wire connected to the internal solder
terminal. This is sometimes caused by the rubber isolator turning into goo and
allowing the internals to slide down inside the tube and stress the transducer
wires. It also could be due to a hard drop of the R-390A since those
mechanical filters are mounted vertically. It is a little tricky unsoldering
the end bells and replacing the isolator rubber but it is not that difficult.
This is my experience but YMMV.Jim
Logic: Method used to arrive at the wrong conclusion, with confidence. Murphy
On Tuesday, August 12, 2025 at 10:58:17 AM CDT, Adam Morehouse
<morehous...@gmail.com> wrote:
Hey Barry,
I have not yet - I wanted to check in and make sure there aren't any
components that should be changed before a test, like the filter killer cap
in the A model.
Adam
On Tue, Aug 12, 2025 at 11:46 AM Barry <n4...@knology.net> wrote:
> Hi Adam,
>
> While I only have a sample size of one R390, I think you may find the
> components in these are much more likely to still be good and there may not
> be that many "replace on sight" components as might be in other radios.
>
> Have you powered it up to see how it behaves?
>
> 73,
> Barry - N4BUQ
>
> > Hey guys,
> >
> > Long time lurker here. You fellas helped me through my R-390A restoration
> > (which just got back from Bill Riches for his finishing touches). This
> > weekend I purchased an R-390, and another R-390A. Both them are are
> pretty
> > pristine - faces are great, extremely clean inside. The R390A has some
> > weirds to the IF deck and Audio deck, which I haven't figured out....the
> > R390 looks untouched.
> >
> > I am not very smart with electronics - I'm a young man, and typically
> > restore old Philcos, Zeniths, etc as a hobby. Replacing caps and
> resistors
> > I can do. Everything else confuses me, but I am trying to learn,
> especially
> > since I've got a growing collection of communication receivers.
> >
> > Supposedly, the R390 went to Rick Mish around 2004 - I think the owner
> > might be confused with the R-390A, as it's cleaner than new inside. The
> > R390 looks untouched. I am sad that there doesn't seem to be as many
> > articles, etc for the non-A...I do some original TM's on the way.
> >
> > In order to test thing, what are the bare minimum caps/resistors to
> > replace? I haven't torn it down yet - I see a 10uF can behind the front
> > cover, and what looks like an oil filled cap near the P/S. Hopefully
> > nothing under the RF deck needs to be looked at, as that seems like a
> bear
> > compared to the R390A.
> >
> >
> > Thanks for any help, or advice. I really appreciate it!
> >
> > Adam K2AAM
> > ______________________________________________________________
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> >
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