[Collins] PM-2 help

[Bob Spooner]

> -----Original Message-----
> From: collins-bounces at mailman.qth.net [mailto:collins-
> bounces at mailman.qth.net] On Behalf Of Dr. Gerald N. Johnson
> Sent: Friday, October 31, 2008 10:49 AM
> To: collins at mailman.qth.net
> Subject: Re: [Collins] PM-2 help
> 
> 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
> 
Another thing to remember when rewiring AC circuits is that the hot wire
from the cord should go to the terminal on the fuse holder that is furthest
from the end of the fuse holder where the fuse is removed. That way if
someone pulls out the fuse without unplugging the equipment, once the fuse
is part way out it can no longer make contact with the hot end of the fuse
holder and cause shock.

73,
Bob AD3K