I assume that you do not have the companion AM-65 audio amplifier?
Shame, because internal to that unit is a power supply (don't remember the
numbers now) that allowed you to operate the AM-65/RT-70 combo from 6, 12 or
24 volts depending on the power supply used. The usually supplied unit used
24 volts (Korean War American military standard elec system). If you can't
get the 12 volt version, modification instructions can be found in a 73
Magazine article called
"New Orders for the R-108" which was a companion receiver for the big
brother of the RT-70, the RT-68. R-108 used the same series of plug in
internal power supplies that the AM-65 did.
There was also a magazine article in the now defunct as well Ham Radio
mag titled "Get on Six Meters-The Easy Way". It dealt with a manpack 6
channel radio of Canadian ancestry that also needed 90 Volts. I have the
entire run of that magazine from 1969 to 1990 on cd. If I can figure out how
to extract the stuff off the disk, I'll email it to you. Now, the fee for
such information.....
You will regale me with tales of operation and modification of
aforementioned Olive Drab garbed electronic equipment!!! I'll email you
later from my own account so that you will get my real email address, or you
can use the arrl reflector. 73
Chris
"James F. Mayer" wrote in message
nk.net...
I need to generate 6v DC and 90v DC from a 12v DC automotive
electrical system to power an RT-70A/GRC surplus military radio. I need
about 250 mA at +6 volts and about 75 mA at +90 volts. I was thinking
about using the guts from an old battery back up but it would be a bit of
a kluge. Are there any 90 volt regulators in the 78xx series? How do I
get the voltage up to where I can get something that I can get the 90
volts from. Getting the 6 volts doesn't seem to be a problem. A 7806 off
the battery should work for that unless any of you can see a problem doing
that. Maybe the common common would be a problem. Right now I'm running
it off of an HP6299A and an HP6236B with commons jumpered. I'd like to be
able to go portable with it.