[ARC5] IF transformers.

[WA5CAB at cs.com]

Ken,

REF NAVAER 08-5Q-4 Figures 37A, 37B & 37C, bottom one third (center and top 
thirds are 239 KC and 85 KC respectively).

First, my earlier statement about the pie thickness was incorrect.  All six 
705 KC pies are the same approximate thickness.

But I'm afraid that some of your statements aren't correct.  All three of 
the IFT's in the 1.5-3.0 receivers (and for that matter the others) use the 
same base contacts.  1 and 2 Primary, 5 and 6 Secondary.  3 and 4 are not 
used in any of the three.  

Regardless of which pins are omitted from the male connectors in the 
chassis (mainly done in later production SCR-274-N receivers, which set does not 
include a 1.5-3.0 MC receiver), you cannot rotate the IFT 180 deg. and plug 
it in.  The pin pattern is 6-pins on an approximately 6-3/4-pin pattern.  The 
distance from pins 1 to 6 is not the same for example as the distance from 
pins 1 to 3.

Balance of comments interleaved.

In a message dated 06/15/2013 19:17:28 PM Central Daylight Time, 
kgordon2006 at frontier.com writes: 
> On 16 Jun 2013 at 11:53, neilb at ihug.co.nz wrote:
> 
> >What I'm building up to asking is this:
> >If a 3rd IF transformer is fitted into the 1st IFT position, does its 
> >primary
> >now get used as the secondary and vice versa?
> 
> Good question. I don't think so.

They do not.  Primary remains primary and secondary remains secondary.

> 
> >The tap? Is it still active
> 
> Not as far as I can tell.

Yes, it is.

> 
> >or does the entire winding get brought into use
> 
> Yes.

No.  If the winding has a tap, the top of the coil is NOT connected to a 
connector contact.

> 
> >(I don't know whether the "top" of a 3rd IFT secondary is actually 
> brought
> >out to a terminal).
> 
> It is.

It is not.  Neither is the top of the primary.

> 
> >
> >If the "top" is not used and the tap is active, does the tap become the 
> B+
> >terminal for the 12K8 plate, the plate terminal itself, the "grid" of the
> >1st 12SK7, or the cold end of the grid winding?
> 
> Dunno. I'll have to look, but these are interesting questions.


In the actual 1st IFT, the top of the primary goes to the mixer plate.  If 
you plug a 2nd IFT or a 3rd IFT onto the 1st IFT connector on top of the 
chassis, the primary taps go to the mixer plate in both cases.  The bottom of 
the primary still goes to B+.  And so forth.

> 
> >Does the radio work well in this condition? There are some conditions
> >that I've just described where it ought not to.
> 
> As I said, I'll have to try it to see.
> 
> However, in this case, as Robert Downs accurately surmised, the outer case 
> was simply 
> installed backwards.
> 
> Ken

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480