[R-390] CV157 manual

[Bill Hawkins]

Roy, sorry to hear you are sick. Let me reinforce your message. 

I had a CV-157 for a time. The madman who sent it to me sent it in
a box for paper towels filled with peanuts. The 100 KC section looked
like something heavy had fallen on it, and I never got it working.

The problem with bringing it up on a Variac is that the rectifiers
are thermionic. No DC will flow until the heaters are at red heat,
near 85% of rated line volts. They heat up rapidly and soon put full
voltage on the caps.

The best thing to do is to use an external DC supply on only the main
filter caps. You have to isolate those caps.

The next best thing to do is to put a lamp socket in series with the
line, assuming you still have incandescent lamps in 60, 100, and 150
watt
sizes. This will save the transformer and regulate current to the caps.

Now, 60 watts may not let a beast like the 157 warm up, so you'll need
to try higher wattages until B+ starts rising. Maybe even parallel
lamps.

Don't pull all of the tubes. There are lower voltage electrolytics that
will get full B+ if the tubes aren't there to load the circuits.

That said, this is military gear, not commercial. It would probably
come right up. A big light bulb in series will serve to protect the
transformer from overloads. A bright bulb means trouble.

And if all you want to do is protect the transformer, then a fuse of
the proper rating will do that. I've seen gear with a copper tube 
where the fuse used to be.

What will you use to test the functionality of the 100 KC auto tuner?

Bill Hawkins


-----Original Message-----
From: Roy Morgan
Sent: Wednesday, February 19, 2014 5:57 PM

have not been turned on for over 20 years and I'll need to bring them up
slowly.

Glenn,

If there are old electrolytic caps in the power supplies and you Bring
It
Up Slowly on a Variac, you may destroy the power transformer.  I have a
diatribe on this but can't get to it now (computer is busted) but
briefly:

An electrolytic cap can reach a limit while reforming that tuns it into
a
shorty circuit.  This overloads the power transformer, and you will not
know it.

Just don't do that.  (Sorry I can't send more information: both my only
computer and I are both sick.)

Roy