Joe posted:
I just acquired a beautiful National NC-240-D receiver without it's
original NC-2TS speaker. I'd love to get the receiver operational. From what I
understand it uses more than a field coil (choke) to connect the B+ in the
speaker to make it operational. I've had previous experience with
Hammarlunds,etc that require a field coil to activate the B+, but I think this
one isdifferent. From what I can tell it actually needs a PP audio output
transformer to make it work.

Would anyone be able to give me any advice on how to hookup a generic speaker
to it? I have both 8 ohm and 500 ohm speakers I can use.
Is there anything I can jumper out, etc to make it work? Any information will
be greatly appreciated.


Nice looking receiver!

The power supply "smoothing chokes" are within the receiver, so you do not need
to concern yourself with that. The factory speaker is a permanent magnet
speaker (no field coil).

However, the PM speaker enclosure needs to have the audio output transformer.
Connector X1 pins has the B+ and the two 6V6 plates.

So you need to obtain an push-pull output xfmr if you wish to use the "speaker
output." The transformer is fairly common even today.

Alternatively, you can use earphones or an external amp by using the earphone
output. The earphone output is taken from the stage preceding the PP 6V6s.

The schematic is available from the BAMA site. Or let me know if you would
like me to email it to you. It's format is PDF.

Don