[ARC5] Re: ARC-5 repair

[David Stinson]

Many years ago, I just assumed most of the caps in the cans were
going to be bad.  But, thanks to talking with "Boatanchor Bob,"
both my thinking and my test equipment have evolved over time. 
The big 3 x .22, which is such a pain to change, 
seems to be good more often than not.
I now gather hacked-up receivers just to salvage the caps, 
and I find a goodly percentage of them to still be good, 
and that's after leaving them under full voltage for several hours.

I now replace the bad ones with "good" ones.
I haven't found many "good" 15 or 5 mFd caps- most seem to
have gone off into the gathering darkness.  
I don't try to "restuff" them, since you'd need a big-bore drill
and a machine shop to get the old one out of the can.
I just nip the wire off, leaving it there, follow the wire to the
connection point, and tack-solder one of the tiny modern caps from
there to ground.  You can do that with the .05s, but it makes
a big mess and destroys any appreciation of the craftsmanship.
However- they're still 60-year-old caps which are prone to fail
if operated for long periods as though they were new. 
 That's another reason I usually run the sets at reduced B+.  
28 volts works fine on my Command Sets. 
90 volts gets you in a better place on the tube curves, 
and I think that's why most other boatanchor receivers seem to 
need around that much.  That our sets will work with 28 volts 
when others need about 90 or so got me to thinking:
Perhaps the A.R.C. engineers were even more brilliant than we know, 
because I'd bet a donut and coffee they "tweeked" the design 
so the sets would keep working into the aircraft interphone,
which would provide an audio boost, 
even if the dynamotors went belly-up.

Regards,
Dave S.