No, but all such failures I'd seen were in Heathkit SB-220's. When the short occurs, it causes immediate and catastrophic "flameage" of the grid RF choke. Because those chokes usually have some sort of waxy coating, they make nice candles :) The smoke will fill the room quickly.
-----Original Message----- >From: kc9...@aol.com >Sent: Dec 22, 2011 11:49 AM >To: w1es1...@earthlink.net, k4...@mindspring.com >Cc: Drakelist@zerobeat.net >Subject: Re: [Drakelist] AC-4R Surprise > >Does the glass envelope actually break? >73, >Lee > > > >-----Original Message----- >From: Steve Wedge <w1es1...@earthlink.net> >To: k4oah <k4...@mindspring.com> >Cc: Drakelist <Drakelist@zerobeat.net> >Sent: Thu, Dec 22, 2011 8:42 am >Subject: Re: [Drakelist] AC-4R Surprise > > >True. > >I've seen 3-500Z's die that way, too, but that failure is usually a lot >more >exciting! You won't find a short with the ohmmeter, but you'll get a >nice bang >when you put the 3kV to the plate :) > >Steve, W1ES/4 > >-----Original Message----- >>From: Garey Barrell <k4...@mindspring.com> >>Sent: Dec 21, 2011 10:11 PM >>To: Steve Wedge <w1es1...@earthlink.net> >>Cc: Drakelist@zerobeat.net >>Subject: Re: [Drakelist] AC-4R Surprise >> >>Steve - >> >>Extremely high gain tubes mean extremely closely spaced grids! :-) >> >>-- >>73, Garey - K4OAH >>St Charles, IL >> >>Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line >>and TR-4/C Service Supplement CDs >><www.k4oah.com> >> >> >>Steve Wedge wrote: >>> If you can find a tube tester, test it. I find that 6HS6's get >shorts more >than most other >>> tubes. They won't show up until you light the filament. My >TV-10-D/U puts >line voltage on the >>> pins to check for shorts (to light a neon bulb), so you wouldn't >necessarily >see a short with no >>> power to it. Not sure why I see so many: if it's something in the >design or >just because many >>> people when they find these tubes are on the way out try to milk >them for as >long as they can >>> because they're so expensive. >>> >>> >>> From: <rhule...@comcast.net> >>> Sent: Wednesday, December 21, 2011 8:54 PM >>> To: <Drakelist@zerobeat.net> >>> Cc: <Drakelist@zerobeat.net> >>> Subject: Re: [Drakelist] AC-4R Surprise >>> >>>> Well, my nose detected burnt smell in vicinity of T4. R61, a >150ohm 1/2 >resistor in the 250 volt >>>> line to V8's plate is burnt to a crisp, resistance is zero. But >why? >Resistance to ground on V8 >>>> pin 5 is 15k per spec. But pin 6 screen grid resistance to ground >it 15k, >vs 90k spec. >>>> >>>> Any advice? 73, Curt KB5JO >>>> >>> > > >_______________________________________________ >Drakelist mailing list >Drakelist@zerobeat.net >http://mailman.zerobeat.net/mailman/listinfo/drakelist > _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
