[R-390] R390A Basics Finished

Fri, 9 Apr 2004 14:55:37 -0700

Hello Michael & fellow BA'ers,
Nice job on reporting all your actions.
IF YOU'RE NOT TESTING THE COMPONENTS THAT YOU REMOVE, I have a suggestion
that I'll be happy to undertake.  I will be happy to test any of your
capacitors that you send me and report to the group the test findings. This
is just for capacitors. All you need to do is tag the suspect component with
the C# and what it was removed from, and where in the circuit it functions.
i.e. C-126, R-390, Audio Module, on cathode of V-106. These numbers or
hypothetical. If you want the components returned, please include return
postage. Please note I stock a lot of NOS mica, silver-mica, and oil filled
caps. I'm working to inventory, centralize, and catalog these components,
including wire-wound and carbon resistors.
Best wishes to all for a Blessed Easter Season.

73,
Glen Galati, KA7BOJ
424 Puyallup Ave.
Tacoma, WA 98421-1317
(253) 272-1061
email: [email protected]
----- Original Message -----
From: "Michael Murphy" <[email protected]>
To: <[email protected]>
Sent: Friday, April 09, 2004 8:16 AM
Subject: [R-390] R390A Basics Finished

> Hi All,
>
> Well folks, I have finally completed the basics on my 1960 Stewart Warner.
> This radio had good synchronization and basically worked on all bands like
a
> normal radio. All tubes were tested as good. I had five problems which
were
> driving me nuts:
>
> 1. The classic stuck ON power microswitch
> 2. I had a weak band (8-16 MHz) with no antenna trimmer action
> 3. Sensitivity to varying wildly day to day. Shorting the hot plate
trimmer
> on the RF coils to ground (Z20x series) would temporarily fix the
problem -
> spark!.
> 4. Cal signals weak.
> 5. I had a a weird audio gain control problem at the top of the range and
> generally low audio gain.
>
> Anyway, I did the did the basic IF Module and Audio Module cap and
resistor
> changeouts and pulled the front panel and did the RF Deck. The power
supply
> was inspected but not touched. 149.9 Volts on E-607. I also did the
typical
> gearset cleaning using Mystery Oill and a lube with Mobil-One. The thing
was
> reassembled. I then did a quick tune up per the manual.
>
> The results:
>
> Main AC Microswitch - The stuck microswitch was indeed stuck but after
> removing it and inspecting it, the contacts were not fused; the u-shaped
> flopper was not flopping. A slight bend to the spring metal that pushes it
> fixed the problem. I cleaned the contacts and re-assembled it, testing for
> contact action as I performed each step. By the way, this switch can be
> installed backwards and it actually still functions. The power wires will
be
> on the wrong side of the switch!
>
> Weak Band - After re-furbing the RF Deck and reinstalling everything, the
> Front End coil assembly was removed from the top of the deck and
> dis-assembled. I simply hit the trimmer with deoxit and cleaned the
> contacts. The band came back and the front panel trimmer now worked on
that
> band.
>
> Intermittent Sensitivity - The paper caps changed in the RF deck
apparently
> fixed this. Just as a precaution, I changed several of the 0.005 1KV caps
> around the RF amplifier too. No idea which one fixed it. Found a weird
thing
> at C257. It was a 47 pF NPO dogbone cap but no C227 at all. I added C227,
> 0.047 uF in parrallel with it.
>
> CAL Marker - Besides replacing the paper caps and a couple of 1/2W
> resistors, I found that the resistors in the plate circuit of the
> multivibrator, R224 and R226 were pretty much cooked and double value so I
> replaced them with 10K, 1 Watt flameproofs.
>
> Scratchy Audio - The audio module got the treatment and I found that the
> front panel audio pot had a value of 5K instead of 2.5K. I must have put
> this in years ago not realizing that the cathode followers could not
> tolerate the DC bias shift. I found the original pot and disassembled it,
> cleaned it and replaced it. This was all it took.
>
> After a quick tune up, the radio is a new beast indeed. All on my list
> responded beautifully. I used the NTE MLR-Series dark orange mylar film
caps
> throughout. These caps are just as inexpensive, available and fit better
> than the Spragues. Here is the data sheet on the NTE caps:
> http://www.nteinc.com/capacitor_web/pdf/mlr.pdf
>
> Next - AGC, Product Detection and Audio improvements.
>
> MM
>
> ----- Original Message -----
> From: "Roy Morgan" <[email protected]>
> To: "Jim Brannigan" <[email protected]>; <[email protected]>
> Sent: Wednesday, April 07, 2004 10:29 AM
> Subject: Re: [R-390] CV-591 Audio
>
>
> > At 07:55 AM 4/7/2004 -0400, you wrote:
> > >I just completed a substantial re-build and alignment of my CV-591 SSB
> > >converter.
> > >
> > >The audio output is still low.  The Audio gain must be fully open to to
> get
> > >any reasonable audio output.
> >
> >
> > There are various arrangements of the audio output and rear panel
jumpers.
> > Study the manual to see if you have the thing set up right.  If I
remember
> > right, one output arrangement delivers 10 milliwatts or some low power,
> and
> > the more normal arrangement delivers rated output.  The normal output is
> > not very high. I suggest you run the line output to a small external
> amplifier.
> >
> > Roy
> >
> >
> >
> > >Is this a drive problem from the R-390A?
> > >Has anyone else experienced this problem?
> > >
> > >Thanks,
> > >Jim
> > >
> > >_______________________________________________
> > >R-390 mailing list
> > >[email protected]
> > >http://mailman.qth.net/mailman/listinfo/r-390
> >
> > - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> > 7130 Panorama Drive, Derwood MD 20855
> > Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
> > [email protected] --
> >
> > _______________________________________________
> > R-390 mailing list
> > [email protected]
> > http://mailman.qth.net/mailman/listinfo/r-390
>
>
> _______________________________________________
> R-390 mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/r-390
>