[ARC5] P-47/SCR-522

Sat Dec 22 09:26:16 EST 2012

My first experience with having to recap a radio was with an SCR-522.  I had scored a brand new in-the-box 522, complete with control head, cables, junction box and dynamotor.  The first time I fired it up, what a shock!  The capacitors started exploding (!).  There would be a POP! and smoke; the case would be split.  Sometimes they would go out by twos and threes.  Usually the force of the explosion would be enough to damage the resistor invariably placed above the cap on the terminal board.  Even if the resistor wasn't fried by the shorted cap, the little gold-plated (?), wax-sealed plug in either end of its ceramic tube would be dislodged enough to make the resistor intermittent.  Those must have been some awfully expensive resistors!

(Hmm, I wonder if this might have been a problem in actual service 522s?)

This radio had apparently been left on the production line when the war ended, because the receiver had never been aligned (!).  After replacing all the caps and many of the resistors, I converted the oscillator to tunable operation and even on the local FM BC station, it was deaf as a post.  Started tweaking screws in the IF cans and whoooOOOOOOOSH! came the rush noise.  

After that, and doing a very well thought-out published conversion to limit the tuning range to 2 meters by removing most of the plates in the variable capacitors -- VERY carefully because of the ceramic shafts; this required disassembly of the variable to be done successfully and this was easy because the rotors were secured to the shafts with set screws -- the receiver worked very well indeed.  

Some time later, I even used the 522 receiver on 2 meter FM, rebuilding it into a dual conversion set using the IF and Permakay filter from a Motorola railroad packset (solid state -- HORRORS!).  Those who were around back then on 2 meters may recall that the biggest problem was getting the ex-commercial radios we all used to cover more than two or three frequencies.... The 522 as-modified and tweaked had incredible sensitivity for a tube receiver, measured at something like 0.5 uV for 20 dB full quieting (I worked in a commercial shop at the time, with access to good test gear); but you had to really hold your mouth right to get it to stay on frequency.  Air currents in the room would cause it to drift.  Even with a metal panel over the front, hand capacitance was noticeable though not as much an issue as the receiver skating off frequency every time the central air conditioning spewed forth from the vent.  I put what I recall was a BC-375 tuning unit
 case over it and that helped some but the drift issue was never completely solved.

The same 522 became my first satellite receiver!  I used it to listen to the first OSCAR repeater, which as I recall was 10-meter uplink and 2-meter downlink.  With a BC-221 or LM, I forget which, as the BFO, it was sort-of-possible to tune SSB and CW signals by warping the freq meter's output across the IF passband.

We did have great fun back in the day, didn't we?  What we learned was invaluable.  And surplus gear was more often than not the means to the end.  Now, we enshrine it.  Where's the fun gone, you may ask....  I do see the point, though.  The stuff has huge historical provenance; and as a trained historian (MA, even; and my thesis was technical, about early radio) I appreciate it immensely.

And back to the P-47... the town where I grew up had a P-47 razorback model sitting in the city park for years, until the Board of Aldermen in their "infinite" wisdumb decided that some kid might get hurt climbing on it, mommy/daddy might sue the city, etc, so they had it cut up.  When that a/c was originally placed in the park after WW2, so I understood, it was complete... over the years though, it had been heavily scavenged.  The rack for the 522, however, was still in the fuselage behind the cockpit, above the tunnel for the turbocharger.  If anyone is interested, there is a photo of that very aircraft, USAAF s/n 42-25199, as the "centerfold" in the book "P-47 Walkaround" published by Squadron/Signal.  It had been the last aircraft left on the flight line when the base closed and was not airworthy; it had been used as a taxi-trainer for ground crew personnel.  The markings in the photo are the same ones it wore when in the park.

73

Mike
W4DSE

--- On Fri, 12/21/12, Sandy <ebjr37 at charter.net> wrote:

> From: Sandy <ebjr37 at charter.net>
> Subject: Re: [ARC5] P-47/SCR-522
> To: mstangelo at comcast.net, "Tim" <timsamm at gmail.com>
> Cc: "ARC-5 List" <ARC5 at mailman.qth.net>
> Date: Friday, December 21, 2012, 10:35 PM
> My best guess would be the ARC-27
> made by Collins Radio.  They were in the T-33A trainers
> too.  (F-80 two seater that uses the British jet engine
> design (Whittle)
> 
> The F-86D version which was the radar interceptor used
> it.  Basic airframe design the same except for the
> radome nose and intake under lower side of radome instead of
> the "open mouth" intake.  The F-86D also had a J-57
> engine which had an afterburner the F-86 fighter did not
> have.
> 
> The old Douglas B-26 bombers we had before going jets, had
> the ARC-3 and the older SCR-522 radios.  Biggest
> problem we had with the older SCR-522 was it was filled with
> Micamold PAPER capacitors!  They frequently shorted
> out. They looked like a large "postage stamp" capacitor but
> were really a paper dielectric!  Eventually you had to
> completely rid the receiver and transmitter of the
> "Micamold" capacitors, drop in some 6AK5's in place of the
> old 9003's to pepup the receiver and they were "OK".
> 
> 73,
> 
> Sandy W5TVW
> 
> -----Original Message----- From: mstangelo at comcast.net
> Sent: Friday, December 21, 2012 5:02 PM
> To: Tim
> Cc: ARC-5 List
> Subject: Re: [ARC5] P-47/SCR-522
> 
> Does anyone know what radios were in Gabreski"s F-86 Sabre
> jet?
> 
> Mike N2MS
> ----- Original Message -----
> From: Tim <timsamm at gmail.com>
> To: ARC-5 List <ARC5 at mailman.qth.net>
> Sent: Fri, 21 Dec 2012 22:45:36 -0000 (UTC)
> Subject: [ARC5] P-47/SCR-522
> 
> Don't know about the rest of the P-47's but here's some nice
> Pix of an
> SCR-522 in a restored Thunderbolt.
> http://www.twinbeech.com/radio.htm
> 
> Tim
> N6CC
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