[ARC5] SCR-183 Transmitter: Essential Knowledge and Tips for Revival, Part One

[David Stinson]

I've been working and experimenting with SCR-183/283
for a long time.  It's the "Rodney Dangerfield" radio-
"it don't get no respect."  That's an injustice, because it's
a very important set with a long and distinguished service
career, spanning 1931 until the end of WWII in U.S. Military
use and years longer outside the U.S. and in the Civil Aviation.
I check-into local AM nets with good reports.

SCR-183 sets made by Western Electric in their Kerney, NJ
plant flew in Jimmy Doolittle's 1942 12-Volt B-25
Bombers in their famous "Bombs Over Tokyo" raid.
The transmitter is simple and, if one pays attention to these
pointers and tips, easy to revive and operate.

If you supply well-regulated B+ the Master Oscillator is
very stable and reliable, even on 40 meters.
I have a BC-230 transmitter which was (slightly and successfully)
modified for crystal control on a 3 MC frequency.
The simple, reversible change works for 40 and 30 meters.
Attached is an .mp3 of BC-230, crystal controlled on 10.110 KC
(5055 crystal, double in the PA.)

Been trying to write a concise-but-through
manuscript for a gentleman for months but keep not
getting it done, because excuses. including the lose of
a thick notebook of hand-written notes, charts and experiment
results.  Makes me sick to my stomach every time I turn
the place over again looking for that book.  Fortunately,
I do have copies of illustrations I saved as files and
posts full of info, some of which was obsoleted/superseded/corrected
in that notebook.   It's got to be here... somewhere...

This thread has inspired me to try try try to FOCUS and
create something useful both here and for him on -183.
So decided to break the job up into smaller bites for here
and flesh it out later for there.  Staying on-task has gotten
very hard, but not impossible.  So enough whining.
  "Your work and patience will be rewarded."

There are a series of issues to investigate/work when
reviving a BC-230/430.  We'll write a post for each
and work through them one-at-a-time.  Some of them,
I'll need to put the rig back on the bench and redo
to work I did long ago, because the charted results
and "current" recommendations are in that blasted
book.  Those charts are probably joining all the other
data in there, stuck in some dark corner where I
probably put it myself, laughing at the old doofuss
every time I look right at it and don't see it.

1.  Inspection and Base Condition.
      Determining basic condition, missing bits,
     lubrication, fixing low-Z grounds, De-Ox-it
      where needed, testing the
     mod transformer, replacing leaky caps etc.
      The base-line stuff we do when starting
      any boatanchor revival.

2.  Deciding what tubes we'll use, how to
      mount them for use.  CW only or CW/AM?
      Filament issues. Intro to Biasing issues.

3.  B+ Power supply needs and issues.
      Regulation required for smooth operation.
      Relay (or relay-ish) keying as-designed,
      recommendations.

4.  Transmitter plug-in coil:  Common issue
      with the Neutralization coil and how to
      fix it.  Pre-setting your coil tuning taps
      and cap.  External matching cap requirement.

5.  Making a Neutralizing tool. Neutralizing.
      Measuring PA current.  Tuning-up.
      "First Light"  and first QSO.

We'll tackle other gremlins as they dare
bother us.  It will be fun.

GL OM ES 73 DE Dave AB5S


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