[R-390] R390A micro-switch saver circuit

[JMILLER1706 at cfl.rr.com]

Someone (I forgot who) replied to me personally that adding a 100-500 
ohm resistor in series with the cap would absorb the spark energy 
better.  But I have always just used a cap (with no resistor) across 
the switch contacts.  Adding the the resistor is a good idea.
Jim N4BE

----- Original Message -----
From: David Wise <David_Wise at Phoenix.com>
Date: Tuesday, March 7, 2006 12:40 pm
Subject: RE: [R-390] R390A micro-switch saver circuit
To: r-390 at mailman.qth.net

> 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
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