Scott Super Special

[Bill Liers]

Hi everyone,

My friend has acquired a Scott Special Communications receiver and we are presently cleaning and evaluating it's condition. We wondered if any copies of the user manual or other technical documents exist and might be available. Serial number JJ256 for those keeping track. The set has unfortunately been stored improperly and been "fiddled" with. We are hoping to place it on life support and possibly get her functional without any original component replacement. Early tests look good. Any assistance would be appreciated.

Photos can be seen at;

http://billsradioden.shutterfly.com/portable/28

regards,Bill

[Norman S Braithwaite]

Bill:

Thanks for the note.  Many of us will be watching for your progress reports!  A nearly correct schematic is published Radio and Television News, September 1940.  If you do not have access to that issue, I can scan and post a scan of this schematic.  Let me know if you have questions.  I have completely disassembled and reassembled a Scott Special Communications Receiver to have the chrome finish replaced.

Norman

[Bill Liers]

Thanks Norman,

We have the schematic from the "Silver Ghosts" Book which seems close, but it may be from later builds as there are a few differences. Would love to see if the one you have is the same. I expect that the Low band RF & IF sections will be close to the Phantom so a few "educated guesses" should get us running.

Bravo on the re-chroming effort. I can imagine that it was a job and a half.

regards, Bill

[Norman S Braithwaite]

Bill:

Interesting.  My copies of Silver Ghosts do not include the schematic for the Special Communications Receiver.  The magazine schematic is reproduced in EH Scott, Dean of DX, Second Edition.  Unless an official Scott schematic turns up (none known to exist), I doubt there are any schematics other than the original and reproductions of the magazine schematic.  There are errors in the magazine schematic.  My notes include the following:

1) Back half of Osc SW/LW switch wafer not shown (haven't rechecked this one).

2) The schematic shows a capacitor between the screen grid and cathode of the Mod I&II tube.  My receiver has separate decoupling capacitors from screen grid to ground and from cathode to ground.  If wired as shown on the schematic, the receiver may produce rather interesting results.

Norman

[Bill Liers]

Norman,

My error, we are using the Dean of DX schematic. So far, we have noticed on the power chassis, the audio interstage transformer is not the type using a balance pot and appears to match my Phantom. Our Mod decoupling is the same as yours and I expect the schematic was in error. Will continue updates as the holiday schedule allows.

Happy holidays, Bill

[Kent King]

Bill -

Norman is correct, the only known schematic is in the Radio & TV News, actually Oct 1940. No manuals or other information exists. I also own a Special and have been through mine replacing all the caps and other issues. Keep us posted on your progress.

Kent

[Bill Liers]

Thanks Kent,

I suppose the schematic we have will have to do. Of course we're taking notes and making sketches as we go. My friend is hesitant to change any components so a best effort was made to reform the electrolytics. The radio was run up slowly on a constant current transformer and monitored carefully at a number of points. Even with many of the adjustment screws well off the original paint mark, Broadcast came in very strong with amazing fidelity from the 12" speaker in the original 13" metal box. Then, a sag in B+ was noticed and one Electrolytic heating up. Power was cut immediately. She'll have to sit until after the holiday while decisions are made on how to proceed. Bdcst, LW and 3 lower SW bands operating.

regards, Bill

[Norman S Braithwaite]

Bill:

One funny thing about pre-war Scott receivers is that they will pick up stations even if they are pretty well screwed up.  The fact that the Special Communications Receiver is capable of picking up stations is good because that indicates that the coils and transformers in the circuit used for the bands selected are all good.  In my experience, there is always an opportunity to improve reception of Scott receivers unless recently gone through by someone who really knows what they are doing.

Unless you have the odd version shown in the Radio and Television News schematic (I'm not sure anyone does), the power amplifier used with the Scott Special Communications receiver is the same as that used by some of the late Phantom models.  Although I would not remove the original filter cans, I would not worry about securing axial capacitors under the chassis in place of the original electrolytic filters (this can be done without any modification of the chassis).  After reforming, some sections of the original filters may still work but given their age they will not hold a form for very long.  They might be OK if used on a daily basis but if left for a few weeks or months between uses, I would not fire the set up without going through the metered variac process again.  Also, many of the original wax-paper capacitors may pass a signal allowing the receiver to work but they may also be passing DC current as well.  If left in circuit, you almost certainly are stressing the receiver (higher currents demanded of the power supply & higher currents through components and tubes) and run the risk of burning out components, not just resistors but much more significantly, low frequency RF windings, IF windings, and audio chokes.  Both Kent and I have removed the original wax-paper capacitors, removed the original capacitor guts, and stuffed new film capacitors in the old capacitor housings.  They look original but perform reliably.

Norman

[Bill Liers]

Norman,

We are in agreement on all points. Of course the owner will be the final word on how the work will be done. In your opinion, would the sets value be adversely effected by expert level re-stuffing and re-capping? I assume not however, this piece may ultimately be sold. 

regards, Bill

[Norman S Braithwaite]

Bill:

If anything, the value of the receiver will be greater if the original wax-paper capacitors are restuffed with new film types provided that the quality of work is high.  When I restuffed the capacitors used in my Special, I melted the guts out using a heat gun (gloves recommended and care must be exercised not to burn the cardboard tube), separated the sealing wax from the bees wax, and resealed a new film capacitor within using the salvaged wax.  The problem with this approach is that the new capacitors are so small that other fillers are required or much more sealing wax is required.  Sealing wax is used in the ends.  Bees wax or parafin is then used over the entire surface to complete the sealing process (cardboard tube is porous).  For the Quaranta chassis, I chose to use a heat gun and appropriate glue for the end seals then covered with parafin.  For other sets, I forgo the parafin cover since the cardboard tube is not being relied upon for moisture exclusion anyway.  FYI, I only restuff capacitors on receivers that are historically significant.

Norman

[Bill Liers]

Norman,

Agree on restuffing only for radios of Historical significance. Thanks also for your process on this. For my M.S. VI, I used a similar technique with silicone adhesive used to bind the new cap inside which I felt would limit "lead migration" over time. Have you completed your radio and have you possibly made any sensitivity / selectivity measurements?

Also, if not too much trouble, I'd love to see the article from Radio and Television.

regards, Bill

[Norman S Braithwaite]

Bill:

Thanks for your note and inquiry.  My Scott Special is operating on all but one long wave band (procured with broken wire on an RF coil that I have yet to repair) but the two highest frequency bands are not yet aligned.  Given the tube complement of the Special, the two highest bands are somewhat novel and not the best available technology for those bands at the time the receiver was manufactured.  I have not made any measurements of sensitivity and selectivity.  I scan and post the Radio & Television News article.

Norman

[Bill Liers]

Norman,

Thanks for the scans, your set looks amazing.

Bill