[ARC5] Re: [Milsurplus] SCR-183 question

Thu, 18 Apr 2002 10:33:15 -0400

Theoretically, due to tracking concerns, none of the receiver coil sets were
interchangeable, unless they had the same serial number as the set. Each was
individually aligned for the set and the serialized. The biggest problem was
BFO tracking, where a LO was used to provide BFO injection as there was no
IF. Coils of course could be re-tuned, but it is something to keep in mind.
I believe that the AA through AS designations more or less were related to
date of contract rather than manufacturer. An AH would be made later than an
AA but not as late as an AS or AR etc.... I also plan on putting a set of
these on the air one of these years. Along with a lot of other stuff, HI.
73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ, 07731
(732) 901-9193

----- Original Message -----
From: "Mike" <[email protected]>
To: "Jack Antonio" <[email protected]>
Cc: <[email protected]>; <[email protected]>
Sent: Thursday, April 18, 2002 8:37 AM
Subject: [ARC5] Re: [Milsurplus] SCR-183 question

> Jack Antonio wrote:
>
> > I'm working toward an SCR-183 setup, the BC-230 transmitter is up and
running,
> > with 5 watts out.
>
> Ouch!  Take care of those rare (due to the audiofools) VT-25 tubes.
> Soon they'll be like VT-4-C tubes!
>
> > Now is the task of building an ersatz TM-172 junction box.
>
> Why not just buy a TM-AH-172?
>
> OK, OK...that's my little joke!  I suspect the junction boxes are
> extremely rare, since the manual for this gear says that normally its
> function would be provided by a junction box built by the aircraft
> manufacturer.  One wonders why the USAAF would want an aircraft to be
> customized at time of manufacture for the installation of such an
> archaic radio set.
>
> > The manual shows the junction box and its schematic, but no parts list.
> > I need to find the value of resistor 143.
>
> I also have never been able to locate that information.  I have looked
> at the USN manual (has more complete info) for the RU-16/GF-11
> equivalent box, but the USN RU/GF-series is *grossly* different
> electrically from the SCR-183/283 and there is no precisely equivalent
> resistor.  The SCR-183 design is far far more primitive in comparision
> to the rather refined (but still obsolete by WWII) design of the RU/GF.
>
> One has to wonder at the incomplete nature of the information in the
> SCR-(*)-183 manuals.  Though the junction box and resistor 143 and relay
> 153 would have likely been provided by the aircraft maker, still
> troubleshooting by a radio tech would likely require knowing the value
> of resistor 143 (in the oscillator/modulator HV supply line) for
> replacement purposes.
>
> > Also in the BD-AO-83 dynamotor, what is the value of resistors 146 and
> > 152?
>
> According to T.O. 08-10-158 for the SCR-AS-183 (and BD-AS-83):
>
> 146 = 5,000 ohms, 2%, 10 watts wire-wound,
> 152 = 1,500 ohms, 2%, 10 watts wire-wound.
>
> Being wire-wound, they have likely changed little in value.
>
> > Again, the manual I have does not have that information.
>
> Check under MISCELLANEOUS ITEMS in the Table of Replacable Parts.
>
> > Lastly, I am assuming there would be no differences between
> > the BD-AS-83 and BD-AO-83 Would this be a valid assumption?
>
> I believe that to be true.  More knowledgable people on the list may
> correct me, but I think most of the many letter distinctions in the
> SCR-(*)-183/283 were due to there being different
> contractor/manufacturers of basically the same gear.
>
> What gets really confusing is all the tuning units whose nomenclature
> varied with the various models.  For example, the tuning unit for 201 to
> 398 kc and 2.5 to 4.7 mc is the C-439 for the SCR-AS-183, but C-379 for
> the SCR-AR-183.  That almost leads one to think that the coil from one
> set was not intended to be interchanged with the same range coil from
> the other set.
>
> It is really amazing that the USAAF and USN continued buying this type
> gear until at least 1943.  The SCR-183 is particularly nasty, though
> today its antiquity of design is appealing.  Of course, you can hardly
> ever find the transmitters with the VT-25 tubes in them anymore.
>
> BTW, I'd love to buy receiver coil sets C-436 through C-440, a
> MC-125/372/390 dial, as well as a TM-AH-172 for my SCR-AS-183.  Also,
> I'm looking for SCR-274-N shock mounts FT-221 and FT-225 for the
> 3-receiver rack and modulator.  I know...fat chance!
>
> 73,
> Mike / KK5F
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