[R-390] Arcing in 25Z5Ws

[Dennis Wade]

Well it sounds like I just got unlucky with NOS tubes, with the
possibility of filter caps going south.

In any event, I'm in need of at least 2 good 26Z5Ws.  Anybody have any?

Looking at the going prices....I'm wondering if it isn't time to
convert to solid state.

Thank you all for your replies

On Feb 17, 2008 6:46 AM, Bob Camp <ham at cq.nu> wrote:
> Hi
>
> The tubes are *rated* for much higher voltages than they are likely to
> see with any rational line voltage. That's not to say that 40+ year
> old tubes aren't a little gassy ...
>
> Bob
>
>
> On Feb 17, 2008, at 8:54 AM, Jim M. wrote:
>
> > Could this be caused by higher than normal line voltages?  This
> > happened to
> > me on a newly purchased radio several years ago.  I concluded the
> > higher
> > line voltages today was a cause.  Radio was designed for 115, today's
> > voltages can go over 120 depending on circumstances, putting added
> > stress on
> > the tubes and other components.  I now have diodes and a high wattage
> > dropping resistor in the power supply.  Jim N4BE
> >
> > -----Original Message-----
> > From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net
> > ]
> > On Behalf Of Dennis Wade
> > Sent: Sunday, February 17, 2008 2:51 AM
> > To: R-390 HF Receiver List
> > Subject: Re: [R-390] Arcing in 25Z5Ws
> >
> > First of all...please pardon the typo...I do know they're really
> > 26Z5Ws  :)
> >
> > Both replacement tubes were supposedly NOS...how unusual would it be
> > to find a shorted tube NOS (although they were packed in 6/62).
> >
> >         Dennis
> >
> > On Feb 16, 2008 7:00 PM, Bob Camp <ham at cq.nu> wrote:
> >> 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
> >>> _____________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/faq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
> >>>
> >>
> >>
> >
> >
> >
> > --
> > Dennis L. Wade
> > KG6ZI
> > Carmichael, CA
> > _____________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/faq.htm
> > Post: mailto:R-390 at mailman.qth.net
> > Unsubscribe: http://mailman.qth.net/mailman/options/r-390
> >
> > _____________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/faq.htm
> > Post: mailto:R-390 at mailman.qth.net
> > Unsubscribe: http://mailman.qth.net/mailman/options/r-390
> >
>
>



-- 
Dennis L. Wade
KG6ZI
Carmichael, CA