RK Henderson ) writes:
I've got an NCX-3 HF xcvr with a fried power supply. The rig's PS
connector is a big, square 12-pole affair. The manual says the poles
are wired like this:

1 -- power switch
2 -- power switch
3 -- -80 volt bias @ 6ma
4 -- 12,6 volt heater @ 5a
5 -- speaker ground
6 -- common ground
7 -- speaker
9 -- +280 volt @ 125 ma
11 -- +700 volt @ 300ma

(the missing poles are unused)

My question: is it possible to fire this rig with my 25 amp Astron
2-pole 13.8 volt PS, and if so, how do I wire it to that big square
plug?

The only way a 12V supply could power that is if the rig was
set up to run off 12v.

There were tube rigs that had little DC to DC converters, built in or
as modules that plugged into the rig, so one could run them off 12v.

But that connector indicates no such thing. There is no place to
feed in just 12V DC, and the fact that it is expecting various voltages
is a good indicator that you need a complete power supply, that
will supply:

3 -- -80 volt bias @ 6ma
4 -- 12,6 volt heater @ 5a
9 -- +280 volt @ 125 ma
11 -- +700 volt @ 300ma

By making the power supply remote, it allows for much more flexibility.
You don't have to lug around a built in power supply, that might be
a waste if you only used the rig at home or in the car.

So you could choose between an AC supply, or a DC supply, and plug
either into that socket. Or, if you ran the rig in the car, leave
the DC supply there, and then bring the rig into the house and
connect it to the AC supply.

Michael