[Heath] Cheyenne and Comanche (MT-1/MR-1) problem

[Alexander N. Gerli]

Hi, gang,

I'm dusting off my old pair. So far, the receiver is really hot and is
still very accurate. Not going to mess with it. And the TX works well too.
I'm using my old UT-1 power supply which I've recapped and re-dioded.

Problem is when I try to interconnect them. If I go my the Manuals for the
pinouts for the short interconnect cable, neither unit will turn on.
Problem seems to be that the filament line appears shorted. Now, I can run
either unit by itself with the UT-1 with no problem at all.

So far, with the plug X to the Receiver into the transmitter rear apron, I
can get proper voltages on the pins with my DMM:

Pins 5 and 6 are the Filaments 6.5VAC
Pin 1 is appx 350Vdc for the RX B+
Pin 4 is the relay line between the units
Pin 2 is NC as no HV is required for the RX

What bugs me is Pin 3 from the TX which is the ground lead. With this
connected using test leads, the filaments short. I have checked the wiring
on both units, and they are wired for 6V filaments, as is the UT-1.

Somehow, there's got to be a wiring error in the manual somewhere. The
Manuals do not mention which power supply is to be used, although I believe
that they hint at the old MP-1 12VDC supply for mobile operation. The UT-1
is clearly the matching supply for base-station operation.

I'm thinking of wiring the interconnect cable with Pin 3 open. The units
are grounded together via the coax cable between them anyway. That should
present adequate ground for the RX B+ line and should not disturb the
filament path.

I've been fussing with this for the past couple of days and so far I
haven't nailed it. It has got to be something simple. I'd appreciate any
thoughts from anyone on The List who runs these neat old rigs.

73,


Sandy AC1Y


Alexander N. Gerli, Sr.
548 Allred Mill Road
Mount Airy, NC 27030-2202

Scotsmen walk about 900 miles each year.
A Scotsman drinks around 45 gallons of Whisky a year.
Scotsmen get about 20 Miles Per Gallon.
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