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
