Hello Simon,

I presume you are talking about the DC plug. The AC (through which the
batteries ostensibly receive charging current while the radio is plugged in
is just a standard AC cheater cord type jack. The goofy polarized bladed
plug and jack were "J502" and "P502" generics. You might be able to find a
Cinch plug..from Surplus Sales of Nebraska or Fair Radio or somewhere; .not
sure of the number but it will have "502" somewhere in its nomenclature. .
Years ago I replaced the jack with a more standard jack to allow me to get
the power to the NiCd charging circuit and I no longer worry about losing
the DC cord with the oddball plug since the jack is now easily mated with a
much more standard plug. You can use anything, even an SO-239 coax jack if
you aren't concerned about convention or appearance . Also I found that
the NiCds Heath supplied were notoriously weak and would only survive,
maybe, a hundred charges. Once I seem to remember I was able to break the
internal short by supplying high current to it and "revitalize" the NiCd for
another 20 or 30 charges but that was it. I built my GR-78 in 1975 and by
the time Heath folded I had probably replaced that darned battery 3 or 4
times and it was fairly expensive as I recall. With the battery, too, I
replaced it with, I think, two 6-volt batteries in place of the internal
battery and it has worked since Heath closed its doors.

Good luck.

Vern W9STB

"Simon" wrote in message
...
Hi

The GR-78 runs from internal Ni-Cad batteries charged through either
240v AC or 12v 2 pin rear sockets. I am looking for plugs to suit one or
the other. Does anyone know what the technical description of these
(other than a Heath part no) and/or a possible source of supply? It is a
nuisance to open up the set to charge the batteries!

Thanks

Simon