[Milsurplus] More on BC375 Tube Subbing

[Lloyd KK7IZ]

Don't know about the BC-375s but I do know that he bought a bunch of Collins 
18S units and turned the parts into marine radios. How do I know? I used to 
rebuild them. There is/was a surplus place at the east end of Old Spanish 
Trail in Houston that bought a bunch of 18S units about 1970. I was there 
when they were unloading them and bought the whole lot. Got my money back on 
the first dynamotor I sold. They were run on the shrimp boats on 32 vdc. 
Kinda took its toll on them. Final was an 813 mod by a pair of 811s. I would 
"rebuild" an old DuBose transmitter for $300. Includes new tubes, caps, mod 
transformer, clean up and paint and a new dynamotor. Had more work than I 
could handle. Finally gave up the hobby as it was interfering with my 
aircraft career.
Incidently if anyone runs onto a TP-250 marine unit built by AR&D or Harbor 
Electronics out of San Diego or an RP-400 from RM Parsons Co, Pasadena Ca I 
would like to know about it.
Thanx
Lloyd  KK7IZ
kk7iz at cox.net

Lloyd Godsey  KK7IZ
1315 N. udall Circle
Mesa, Az  85203
480-620-7145 (cell)
Visit my  web site
www.lloydsdipsydumpster.com
And my NEW  web sites
www.antiqueradioarchives.com
www.antiqueaircraftradios.com
Collecting OLD civilian aircraft radios and literature
Particularly Lear. Got anything?
Some boatanchors got wings

----- Original Message ----- 
From: "Skip Frolik" <frolik at gulftel.com>
To: "'Milsurplus New mailman'" <milsurplus at mailman.qth.net>
Sent: Tuesday, June 07, 2005 12:57 PM
Subject: RE: [Milsurplus] More on BC375 Tube Subbing


> Dubose converted BC375's for use in the 2-4 MC Marine Band
> along the Gulf Coast. They used 838's as the modulators.
> Course they also changed out the 211 in the final to an 813
> along with a better rf chain and speech amp so other "Fine
> Tuning" was incorporated. Bottom line for mentioning this
> is that for the most part "Most" of the 375 was kept intact
> so apparently at least in the modulator stage this was a
> win-win situation.
> Skip
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net]On Behalf Of David Stinson
> Sent: Tuesday, June 07, 2005 11:39 AM
> To: Milsurplus New mailman
> Subject: [Milsurplus] More on BC375 Tube Subbing
>
>
> While getting the SCR-287 ready for W5E in April, I subbed
> an 838 triode in both the oscillator and power amplifier stages of the 
> 375.
> The 838 physically looks like the 211, with a more robust mechanical
> structure. It costs less than half what one would pay for a NOS 211.
>
> The 838 is a "zero bias" triode amplifier, while the 211
> is a more conventional triode.  It also has a somewhat different
> interelectrode capacitance.  After re-neutralizing the PA,
> the 838 seemed to work just fine in the final.
> In the OSC stage, it appeared to be somewhat less
> stable, but I didn't really give it a proper warm-up.*
>
> Does anyone have any thoughts on using this tube
> as a lower-cost substitute for the VT-4 / 211?
>
> 73 Dave S.
>
> * as an aside- once the 375 had run for a couple of hours
> prior to the W5E event, it became quite frequency stable on 3880 KC.
> After two hours, I never had to correct it again.
> But then, I did hand-pick the oscillator 211 for stability,
> so that may have been a factor.
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