[Boatanchors] Blowing fuse on Valiant

[mikea]

On Mon, Dec 31, 2007 at 03:56:21PM -0500, Joe Roth wrote:
> 
>    I  have  a  Johnson  Viking  Valiant.  It worked fine. I know I should
>    replace  the  original  caps, so I got the kit from K1TLI and did just
>    so.
>    I  triple checked my wiring, etc. But now it bows F2 (primary for T2).
>    It  blew  twice  now.  Both times it took about 5-10 seconds before it
>    popped.  There  was  not any hiss, smoke, or cracks. Quietly the tubes
>    lit up as normal and then it shut down.
>    Suggestions  on  trouble  shooting from the experts? Bad 6BY5 maybe? I
>    would more than welcome a phone conversation as well if needed.
>    TNX Happy New Year!

Hi, Joe. That sounds to me as though something downstream of the
rectifier is shorted: until the rectifier starts working, there's
no voltage across the components downstream of it; once it heats up
and starts passing electrons, there's a low-R path to ground, and
the fuse takes the hit. If it's a slow-blow fuse, it may last a few
seconds before it dies, pulling overcurrent through the transformer
and maybe doing damage to other stuff. It's good that the fuse is
taking the hit; I've seen altogether too many of them rescued by some
semiconductor heroically sacrificing itself.

I'd pull stuff loose from the rectifier output and check it out. I 
don't have a schematic here at work, and the web proxy won't let me 
get to one. If there's a choke, it may check OK until it sees enough 
voltage to arc to the case. Caps probably will be easy to find. 

And, as someone else replied, pulling the rectifier tube is the cheap
and fast way to see where the problem is. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin