[Heathkit] MT-1 Cheyenne and MR-1 Comanche.

[Mike Olbrisch]

Progress!

The HP-20 power supply was the first big worry.  The power cord was in bad
shape, cracking and brittle - the plug had 2 fuses in the plug, but the
plastic of the plug was in bad shape and was held together with electrical
tape.  I replaced it all with a 3-wire computer cord in its place, with a
fuse holder mounted in the underside of the cabinet, in the black hot lead
of course.  Then it was time for testing.

As of this moment I believe the Power Supply is OK.  Not 100% certain, and
here is why.

+600v is really +740v
+300v is really +320v
-150V is really -170v

I had the P/S running unloaded for about 5 minutes.  When I was done probing
the voltages I shut it off and picked it up to move it.  The right side of
the upper cabinet was very hot.  There is a large wire-wound resister in
there.  Is it normal for it to run so hot that the outside of the metal
cabinet is hot?

I suspect that the higher voltages and perhaps also the heat is because the
supply was unloaded.  My next step would be to try powering up just the
receiver and see if it can hear anything.

Anyone out there got experience enough on the HP-20 to tell me if this is
normal?

Thanks a bunch.

Mike.