[Collins] 75S-3 "BFO TEST" jack

[Dr. Gerald N. Johnson]

Its not in the 4th edition manual that I have downloaded.

Be sure that the product detector mods weren't from service bulletins or 
the ASAB (Amateur Service Agency Bulletins). And remember than the 
75S-3A is just a 3 with the extra crystal bank.

One other sign it was original would be that its nomenclature is silk 
screened on the chassis and with the same font as the rest of those 
labels on the top of the chassis. Mods and prototypes were sometimes 
labeled using rubber stamps and paint and are less consistent than the 
silk screens.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association

On 10/29/2010 9:10 PM, Bob and Sue Jefferis wrote:
> Greetings,
>
> I just acquired a 75S-3A that has the "BFO TEST" jack in the chassis. The jack hole was punched, the jack label is there, and original, the jack itself, and the mounting screws are perfect matches to the HFO and VFO chassis jacks. Even though this jack is disconnected, there are red Glyptal [sic?] artifacts on the center post. So, I am currently believing that this jack was installed at original build time.
>
> I discovered that a previous owner made some very curious modifications to the product detector and BFO. I think the BFO TEST jack may have been disconnected during these mods. I have 2nd and 3rd edition manuals, but this jack is not shown in them, both the photos and the schematics. Does anyone have a first edition manual or hands-on experience that would tell me how the jack was originally connected? I would like to put it back to "stock" configuration while I undo the product detector mods etc. Thanks for any help here.
>
> Bob, KF6BC
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