[R-390] Arcing in 25Z5Ws

[Dennis Wade]

Good evening all,

            Recently I flipped the power on to my trusty Motorola
R-390A, and instead of the comforting sound of HF radio, I hear
nothing, and see a couple of blue-white flashes.  Because I all the
covers were on and where I was standing, I couldn't see just where the
flashes came from.  When looked at the fuses, the 1/4A B+ fuse was
blown.

             After a brief detour to replace a cracked fuse holder and
a physical inspection, I replaced the B+ fuse and flipped her on
again.  Nothing.  The main 3A fuse went too.  Replace that.  Now it
lighted up, but no sound.  All the fuses held too.

              Now I pay more attention to what's lit and what's not.
I noticed both 25Z5s were dark, and after flipping it off again, cold.
 Replaced both.  Now one is lit, but not the other.  Swap tubes...same
tube is lit in the other position, and now the tube starts to arc
inside.  Hear a 60 (120?) cycle buzz now too, but nothing else.  Turn
power off quickly.  Fuses all held.

              Anybody have a guess as to what's going on?  Do I just
have some bad rectifiers, or has something else gone south and taking
the rectifiers with it.  I'd rather not feed it rectifiers if they're
not bad to begin with.

                  Opinions welcome.

                  Thanks!

                     Dennis



-- 
Dennis L. Wade
KG6ZI
Carmichael, CA