[AMRadio] Protecting receiver (was WTB: Coax relay, 110VAC, aux contacts)

[Robert Nickels]

On 11/19/2011 9:04 AM, Rick Poole wrote:
> This relates back to something someone else said about being exposed
> to 110VAC on the relay coil connections, a shock hazard... with the
> Hammarlund, the actual B+ to the first few receiver stages is routed
> out the accessory connector and back in again, posing yet another
> shock hazard since it could be easy to get across that at the wrong time, too.
That was me, so I'll chime in on this too - as I don't like ANY 
"shockable" voltages running between pieces of equipment, on exposed 
screw terminals, etc.
(Those with cats, small children, or wayward fingers will understand why!)

One solution I've used on several receivers that switch the B+ for 
muting is to install a small external low-voltage relay on an angle 
bracket at the rear panel to do the B+ switching.  This slave relay can 
be actuated by an external switched voltage, or by a wall-wart in series 
with the external contact closure.   (Or, as I usually do, but simply 
rectifying and filtering the filament voltage, via one wire run through 
an existing hole.  The whole thing is easily removable without a trace 
and while it's always a good idea to make sure all power is off before 
touching anything, this just makes me feel safer, plus it standardizes 
the muting connections fif you want to play with different receivers.   
Suitable relays are a buck or two from Mouser, etc.

73, Bob W9RAN