[Collins] PM-2 help

[Dr. Gerald N. Johnson]

On Sat, 2008-11-01 at 00:29 +1030, spock wrote:
> Hello Everyone
> I am wiring  the ac power input to the PM-2  Is it normal for the hot side of 
> the filament winding to be soldered to tb6 ( this is the 3 terminal board on the 
> edge of the chassis next to the 115V/230V switch) it also has two wires from pin 
> 8 and 9 of P2 which are colored solid white with black strip, if not where are 
> they soldered to together?  Where is does the wire at the back of the 4 amp fuse 
> go? is this where the neutral ac line is to go?  this is the first time I have 
> worked on the PM-2 power supply and it was supplied to me without a power cable. 
> Your help please.
> 
> 73 Lee 
> 
I'm not sure about the PM-2, but some early Collins supplies were wired
with the fuse in the neutral which is contrary to safety codes. The fuse
and switch should be in the hot side, so that when open, voltage is
removed from the wiring beyond them.

Basically the line cord neutral wire (usually white insulation) should
go to the transformer primary (and there will be a wire from the 120/240
switch). The line cord hot wire (generally black in color) should go to
the radio connector to go to the power switch. The wire from the power
switch goes to fuse and the other side of the fuse goes to the other
side of the transformer primary (and there will be another wire from the
120/240 volt switch there). That way all the wiring beyond the switch
will be at ground potential with the switch off. A safer condition for
poking fingers.

I suspect early supplies didn't have three wire cords or polarized plugs
so there was no way to enforce the switch in the hot side and when a
draftsman changed the assembly drawings to connect up the three wire
polarized cord, he didn't realize which way was safer. I KNOW I had to
argue with draftsmen at Collins about RF symmetry details that was
beyond their comprehension of circuits.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer