[Hallicrafters] S20R BFO dead

[Roy Morgan]

On Apr 23, 2009, at 9:23 AM, SX-25 wrote:

> ...the coil is a cantankerous component and, excepting for one,   
> every SX-25 I have restored (6 so far) has had a problem with the  
> coil. ... If you don't have continuity through the coil, don't be  
> afraid to sacrifice a turn to produce enough wire to strip enough  
> varnish and resolder to the terminal.

Neat trick that I have not tried yet:

Place an aspirin tablet under the varnished end of the tiny thin wire  
- single strand or Litz wire.  Apply a bit of solder with the solder  
iron so the aspirin acts like a flux.  This is reported to be the  
simplest safest way to tin the thin wire used in coils.

I'd rinse with water (or Windex, my favorite cleaner) after soldering.

Note:
Litz wire is normally 7 (sometimes 9) strands of VERY thin wire all  
twisted together.  It's found in IF coils and the like.  It turns out  
(pun) that even missing one of the strands as you solder it reduces  
the effectiveness of the wire by quite a lot.  The Q of the coil might  
be reduced by 20 or 30 percent.  The aspirin tablet trick above can  
make it easier to get a good connection than stripping the teensy  
wires with a sharp exacto knife.

Roy


Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073