[R-390] Arcing in 25Z5Ws

[Bob Camp]

Hi

My *guess* is that you have a filament to cathode short in the '"bad"  
tube.

Bob


On Feb 16, 2008, at 9:22 PM, Dennis Wade wrote:

> 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
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