[R-390] R390A micro-switch saver circuit

[David Wise]

Apologies in advance because I haven't seen the triac circuit.

It can't supplant the switch by itself; triacs are hellish RF emitters.
It would have to close only for the short periods of time covering the
points at which the microswitch opens and closes.  You might as well
use a relay.  (Electromechanical type only.)

The cap, especially if enhanced into an RC snubber, is the ticket IMO.
There's stuff on the net for computing values, but since we don't
know the requisite transformer parameters, just cut-n-try until it's good enough.
I don't know why Collins didn't do this; it's a well-known technique.

Dave Wise

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Jim M.
> Sent: Saturday, March 04, 2006 8:46 PM
> To: Perry Sandeen; r-390 at mailman.qth.net
> Subject: Re: [R-390] R390A micro-switch saver circuit
> 
> 
> I hve found that a simple .01 ufd 1 KV disc cap put across the switch 
> reduces arcing a lot and can extend the life of any AC switch.
> 
> 
> 
> ----- Original Message ----- 
> From: "Perry Sandeen" <sandeenpa at yahoo.com>
> To: <r-390 at mailman.qth.net>
> Sent: Saturday, March 04, 2006 10:43 PM
> Subject: [R-390] R390A micro-switch saver circuit
> 
> 
> > Hi Gang,
> >
> > I've come across another circuit that may be useful to R390A's in 
> > particular and BA receivers in
> > general.
> >
> > When we used the A's in Turkey they were usually on 24/7.  
> Now days it's a 
> > completely different
> > story for most of us.
> >
> > It is a gated triac power on circuit from the 2/06 issue of 
> Audio Express 
> > magazine.  It will
> > greatly reduce the current through the micro-switch which 
> is getting 
> > scarcer by the day although
> > Hank Arney still has some NOS.  Reply off list and I'll 
> send you a pdf 
> > file.  Regards, Perrier