SP200 Mods and Questions

[Steve White]

Sure enough, once I opened up the bottom I could see that there was a
partial recap done a long time ago.  Probably when the mods were done to the
radio.  So I have several electrolytics and a lot of .05, .01 and .1 to
replace.  Think I wills start there and then make a determination what to do
next.  There were mods done to the audio section too it seems.  But no
miniature tubes under the chassis at all.

Steve  NU0P

-----Original Message-----
From: Boat Anchor Owners and Collectors List
[mailto:BOATANCHORS at LISTS.TEMPE.GOV] On Behalf Of Al Parker
Sent: Saturday, May 23, 2009 7:37 PM
To: BOATANCHORS at LISTS.TEMPE.GOV
Subject: Re: SP200 Mods and Questions

Hi Steve,
    Congrats on finding an interesting rcvr.  They make good band cruisers, 
have great audio, and reasonable selectivity.  I like the variable 
selectivity function, as well as the xtal phasing.
    There were a number of articles in the 1960's re: mods to these rcvrs. 
If you can get an April, 1961 CQ mag, there are 2 in it, "the Ultimate 
Conversion of the Super Pro Receiver" by C E Reed, W6FHB, and "The Single 
Tube Product Detector" by Paul Lee, W3JHR (not specifically for the SP-200 
but applicable).
    The former was a major rework of most stages, in steps (sort of).  He 
used 6SN7's for the 1st "Infinite" detector, V8, and the Noises Limiter, V9,

as well as a 6BE6 as Prod. Det., V10.  He completely changed the RF section,

minimal changes in the IF.  The latter, by Lee, used a 6BE6 for the prod. 
det.
    Paul Lee also had one entitled "Save your Super-Pro for SSB" in the 
Sept., 1958 CQ, using a 6BE6.
    Somewhere I have the schematics included with a modified BC-779 I have, 
that has a prod. det. & some other mods.  I couldn't come up with them 
tonite, but I know there here in this morass somewhere.  Those mods were 
said to be done on this rcvr in Taiwan while the previous owner was station 
there 'many' yrs ago.  One of these days I'll get a round tuit & see how it 
performs.
    I can scan those CQ articles for you if you can't find them somewhere.
    I refurbed one of these a few yrs ago, but left it basically stock.  My 
experience with that one can be seen at 
<http://www.boatanchors.org/SP200.htm>  I just found some notes on a 
schematic for that endeavor that show a little more info than on the 
webpage.  20 caps replaced (paper & electrolytic), less than 5 showed no 
leakage at 25vdc, but all did have leakage at 150-200vdc.  I also replaced 
many resistors that were 10-20% or more off value.  Hopefully your recvr has

had all that taken care of before this.
    I'm cc'ing this to a friend who also picked one up a Dayton last wk.
73,
Al, W8UT
New Bern, NC
www.boatanchors.org
www.hammarlund.info

"there is nothing -absolutely nothing- half as much worth doing as simply 
messing about in boats."
   Ratty, to Mole


----- Original Message ----- 
From: "Steve White" <Stever2k at MCHSI.COM>
To: <BOATANCHORS at LISTS.TEMPE.GOV>
Sent: Saturday, May 23, 2009 12:06 PM
Subject: [BOATANCHORS-TEMPE] SP200 Mods and Questions


> Hi Everyone
>
> I picked up a functional BC779 or a SP-200 at Dayton and it has some
> different tubes in it than what is in the manual.  Most notably the IF 
> amps,
> 6k7 have been replaced with 6SN7's.  There is also a mod to the detector
> circuit of some kind.  Where the headphone jack was there is a rotary 
> switch
> installed which affects the demod...Product Detector perhaps?
>
> Is anyone aware of a mod that would replace the 6K7's with 6SN7's or was
> this a change in the manufacturing?  It is serial number 762.  Or is 
> anyone
> aware of a mod that used the 6SN7 in this application.  The tubes are
> considerably different beasts.
>
> Any input would be most helpful
>
> BTW it is cleaning up very nicely and without any work it seems to work
> pretty well.
>
> Steve NU0P
>
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