[Milsurplus] power requirements

[Mike Morrow]

>However, the 46104 is wired the same way and has the same power requirements 
>as any other ARA or SCR-274-N receiver.  Probably a bzillion places on the 
>internet where the schematic and information (or in some cases disinformation) 
>has been posted.  About 30% of them will be wrong in one respect or another but 
>if you look at ten and take the seven that agree you'll probably have it 
>right.

The CBY- or CCT-46104 is a good case in point.  As near as I can tell, ARA schematics for all five receivers are listed on several mil list sites, each with their onw individual unique URL.  But examination shows that ALL dipict the only the CBY- or CCT-46106 6.0 to 9.1 MC receiver.  There are some significant differences in the way things were done on this range of receivers, mainly in IF stage coupling, compared to the other ranges.  It would be much more honest if the various schematic links pointed to the same URL, rather than multiple URLs that all show the *same* model. 

>And a tip, do not ever under any circumstances ever solder to any of the male 
>mini-banana pins.  From the standpoint of destroying the receiver, you might 
>just as well drill holes all over it.

Though I've never seen it pointed out, it may be worth mentioning that the connections made at that front-panel 8-pin connector also vary between models and versions.

1.  HV POWER:  Except for the BCB BC-946-B receiver, designed to supply power to the R-1/ARR-1 through a FT-310-A power adapter panel, none of the other SCR-274-N receivers provide high voltage at the front panel connector (pin 8).  But the ARA and AN/ARC-5 models all do.

2.  AF OUTPUT:  None of the AN/ARC-5 receivers provide AF *transformer* output to the front panel connector (pin 4).  But the ARA and SCR-274-N models all do.  Instead, AN/ARC-5 navigation receivers (R-23, R-23A, R-24, and R-148) provide a filtered audio signal from the cathode circuit of the AF output tube to pin 4, designed to send ILS localizer receiver AF to the AN/ARN-9 Air-Track ILS through the MX-19/ARC-5 ILS adapter panel.  The other AN/ARC-5 receivers have no connection to pin 4.

Every old ham-compendium of "command set" characteristics that I've ever seen burps out some arbitrarily selected SCR-274-N receiver, transmitter, or modulator schematic and pretends that the schematic will apply to any item that one comes across that looks even vaguely similar.  As Robert mentions, they usually don't to varying degrees.  Try applying a BC-456-B modulator schematic to a MD-7/ARC-5!

Mike / KK5F