[R-390] Metal Paper Caps?

[Michael Murphy]

Hey Tim,

I had to change out one of those round metal triple-caps on a command set RX
myself, last weekend. It was on the the B+ feed of the BFO. The BFO would
run for a while, warble for a few minutes and then quit all together. Normal
voltage on the cap was supposed to be about 180 VDC. It turns out that the
BFO had around 27 VDC when it was functioning "normally" and 14 VDC when it
would warble. Below that it would finally quit. Now that is overdesign. With
a new cap the voltage returned to the nominal 180 V. The command set was
last weekends project.

This weekend I brought a Sky Buddy back to life for a "buddy" at work. It
had some bad caps of course and a little creative modification or two which
had to be undone, but it came back and I was listening to AM and CW all
afternoon on it. What a simple box! I think this was a 1938 design, but it
is a late model S-19R with the more modern tube lineup. 6K8, 6SK7, 6SQ7 and
a 41 in the PA. The BFO is a separate 76 tube. It has a "real" power supply
with a type 80. I am keeping it long enough to use it at the end of the
month in the AWA Linc Cundhall Memorial OT Contest which is CW only,
pre-1946 only.

I see you are getting into HBR's. I have not done that yet, but I am on the
lookout for a carcass to rebuild. My latest craze is re-discovering
Q-Multipliers. I just built two, one for my TCS at 455kc using a single 6J5
which is a "peaker" and one for the 3-6 McCommand set for 1415 kc IFs using
a 12AT7 which peaks and nulls. Wow! is all I can say; almost enough to make
my R390A a little nervous.

Mike WU2D

----- Original Message ----- 
From: "Tim Shoppa" <shoppa_r390a at trailing-edge.com>
To: <r-390 at mailman.qth.net>; <kf4yio at charter.net>; <chacuff at cableone.net>
Sent: Saturday, January 14, 2006 1:44 PM
Subject: Re: [R-390] TIRED OF READING ABOUT CARDBOARD SPEAKERS


> "Cecil Acuff" <chacuff at cableone.net> wrote:
> > What are some of the other group members current winter time
projects.....
> > We'd love to hear about them!
>
> Making a HBR-16 type receiver from scratch is mine. Been tearing through
> junker BC-453B's for IF transformers. For those who don't remember,
> the HBR-series of receivers were in QST articles in the 60's, and are
> dual conversion (1.6MHz first IF and 85kHz second IF, adjust to fit
> whatever IF transformers you can find.) Have a nice big Millen dial
> and VFO put together already, and have been sweeping out and tweaking IF
> transformers for eventual use. qth.net also has the HBR mailing list,
> I highly recommend it as well as the HBR site: http://k5bcq.edebris.com/
>
> I know the habit here is to talk about brown beauty caps, but the
> paper-caps-in-metal-cans in my BC-453B's make brown beauties look good
> in comparison! In many cases the metal cases are leaking green gunk
> (or, they have been leaking gunk for a couple decades now.) I didn't
> know that paper caps had that much gunk in them!
>
> I still have my project from summer to wrap up too, the yellow-striper
> R-390A from Fair Radio. All the modules are cleaned up, recapped,
> and re-aligned, and work in my other chassis, but haven't quite put
> the banged-back-into-shape chassis from Fair back together yet (there's
> actually some banging still to be done on the back panel - the front
> panel has been done for half a year now!)
>
> Realistically these projects will stretch into summer too.
>
> Been on the air with my Ten-Tec Triton IV on CW recently. It's sweet
> on CW w/break-in, but no tubes!
>
> Tim.
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