[AMRadio] NC270 Muting

[C.L. Mitchell]

Got a chance to look at a schematic for the NC-270.  The 'standby/receive' switch opens the +145 VDC line from the power supply, which effectively shuts down most of the radio.  The other section of the DP switch shorts the rear apron terminals.  You could change the wires going to the rear terminals to across the section of the switch that controls the low B+ line and switch it with an external relay, etc; leaving the 'standby/receiver' switch in 'standby' to use external switching.  The drawback to this is 145 VDC floating around on the control wiring.  I personally would, and have in some of my receivers, install a small low voltage relay in the National and use it to control the low B+ line as above and control the relay with external switching.  You can always pick up low voltage from the filament winding on the power transformer.  Hope this helps.
 
73,  Mitch
K9PNP
 

> From: rwpeters at swbell.net
> To: boatanchors at mailman.qth.net; boatanchors at puck.nether.net; amradio at mailman.qth.net
> Date: Thu, 7 Apr 2011 09:56:43 -0500
> Subject: [AMRadio] NC270 Muting
> 
> Hi Guys... Have a Natoional 270 and need to know how to mute it... It has
> relay screws in the rear but when shorted do not work...
> Any ideas????
> 
> 
> Very Best 73's
> Bob Peters
> W1PE
> 
> ARRL, QCWA, AM FOREVER
> 
> Money is only temporary, Radio is forever
> >From The Old Dog
> 
> 
> 
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