[ARC5] Power up Modulators

[Jack Antonio]

I second everything David said, plus a couple of others.

1. In checking the can capacitors, check for leakage between
the individual caps as well as leakage across each cap. I have
seen a few caps where each capacitor checked OK from its terminal
to ground but there was significant leakage inside the can from one cap 
to the next.

2. Run all tubes through a tube checker, mainly looking for
the gross problems, like shorts or no emission. This step
would have saved me around half an hour inside a BC-454.
(It was a heater to cathode short, which killed the gain
control line)

3. In the modulator, check C-54B( in the BC-456, I don't have the
info handy for the MD-7/ARC-5), most of these I have seen
have lost capacitance, and this will kill audio gain in
the modulator. Also check C-57, this is an arc suppression
capacitor, and if it is low in value or leaky, can cause
some severe arcing in one of the relays. (The arcing destroyed
a relay in an MD-7 I have).

4. On the air variable caps in the transmitter, check to see
that all the little glass bead insulators holding the stators
in place are there.

5. In the transmitter, check R-76 closely. This is
a 20 ohm resistor made by winding some small wire
around a ceramic body, and it tends to act as a fuse,
I have run across a number of open ones.

But first, spend a couple of hours reading the posts
in the ARC5 mailing list archive. Lots and lots of
useful information and interesting reading there.

Jack Antonio WA7DIA
scr287 at sbcglobal.net




David Stinson wrote:
> Tom Dawson wrote:
> 
>> Looking for caveats and gotcha's regarding powering the modulators and 
>> transmitters up after so long in storage.
> 
> (and receivers, I assume)