[R-390] Mech filter repair, big knob refurb

[Tim Shoppa]

OK, I'm taking stock of my yellow-striper from Fair Radio.

They were pretty quick about getting it to me and did a great job
packing it.  Despite the packing job one tube (a 5814A) did get
cracked in shipment.  There's other physically-banged-up-damage
that obviously occured far earlier in its life - a corner of the front
panel is a bit bent, the side panel and back panel of the mainframe show
some evidence of it getting dropped on a back corner, etc.

The guys at Fair Radio did a pretty good job checking it out even
though it was a "Used-reparable" and not a "checked" unit.  Green dots
on the power supply, IF, and AF assemblies indicate that they
actually were checked before shipment.  The green dot on the IF says
the 8KC filter is broken, but actually it's the 4KC filter.  That's
not so bad - I'm likely to use 8KC or 16KC when listening to
MW and SW broadcasters, and to shift to 1KC when listening to CW.
(SSB and I have never got along).

Some knobs, pots, and fuseholders were broken but Fair shipped
me a little box with suitable replacements.

Both the main tuning (MC and KC) knobs have some damage.  Between
the two of them I can swap a clamp around and get a good one.  The
other one, which has damage to the slotted part, I will probably
drill out, insert a piece of stainless steel tubing, slot the tubing,
and put a non-original clamp on.  I think I saw this method of
repair mentioned here before... any advice before I start hogging
away with the drill press?

And the 4KC filter is open circuit on one end.  The other end measures
about 50 ohms.  I guess this means that either the really skinny wire
has come undone or has burnt out.  Is mechanical filter repair by
an average guy like me feasible?  My guess is that the mechanics
are still in good shape and I all I have to do is somehow replace
the skinny wire.  But I don't know how to begin.

Oh, and the guys at Fair already replaced the killer cap in the IF.
Ohming around the resistors in the modules shows some leaky caps and
out-of-spec resistors that I'll probably take on next.

Incidentally, Fair claims to be out of big knobs, big clamps, and
IF filters... not coincidentally what my unit needs :-).  But I'm
sure I'll figure something out.

Tim.