An 811 is a tube from the 40s, I recall a Western Electric KW broadcast transmitter that used a pair to modulate a pair. It was a brute. To my knowledge tube testers were not intended to test transmitter tubes.maybe a TV fly back tube The way to test them is in a transmitter noting the watts in and watts out. As a tube ages the filament may loose it's emission. some times boosting the fulfillment a volt or two will squeeze a little more life out of them, I used to work with a 50KW TV transmitter, a new tube was under voltage on the filament and when it was finished a year or so later it would be 10 to 15% over specs.Another problem is gas that boils out of the plate, Carbon in this case. The Thoriated tungsten filament is designed to absorb gas. just leaving the filaments on for a week or so might remove gas. Sometimes you can see the gas in the tube as a neon like flicker, The following test is not for those do not know how to work with with high voltage, one hand in the pocket, stand back and more, they should run from my advice about testing with 700 volts or so. To test a tube you might use a 700 volt supply and adjust it to the value in the specifications First apply bias to the grid using a ma meter to monitor both plate and grid. More negative bias means less plate current. This is a DC test that does not account for what RF is asking the tube to do. Some times a tube was unuseable in the final but would work ok for a while as a modulator. K5VGM WI2XLJIn a message dated 7/29/2020 2:15:55 PM Central Standard Time, bvarc@bvarc.org writes: John, Fondren EPO's tube tester hasn't worked for years. They'd love to have someone fix it - nice project for anyone intersted - call Chris. Gus, KG5OFB On Wed, Jul 29, 2020 at 9:02 AM John Mechura via BVARC <bvarc@bvarc.org> wrote: Greetings, Unfortunately my tube tester is too new to test this tube. I would recommend contacting Chris at EPO, Electronic Parts Outlet, to ask him if his tube checker can test this tube; if it is listed on his chart. He has a stand-up tube tester such as would have been at drug stores of my youth. The 811 is a triode, utilizing a thoriated tungsten filament as a cathode. As Rick suggests, an ohm meter check of the filament / heater should test for continuity. Then check for shorts between filament, grid and plate, there should not be any. Pins 1 and 4 are the filaments. Pin 2 is unused. Pin 3 is the grid and the plate is on top. Look and see if the plate shows signs of discoloration or overheating. If the silver getter coating inside the glass is silver and not white then the tube is holding a vacuum still. The specs are here:www.radiotechnika.hu/images/811A.pdf My e-mail is:john.mech...@gmail.com 73 John, KI5HOC On Tue, Jul 28, 2020 at 9:42 PM Rick Hiller <rickhille...@gmail.com> wrote: Couldn't you simply just measure pin to pin and compare one tube to the others? Find the odd guy(s) out that way. Then, stick them, one by one, in the "tube testers" from Ameritron, the 811 or 811H. HI John, HOC, is the tube guy.....he will know....73...RH On Tue, Jul 28, 2020 at 9:18 PM Jimmy Vance via BVARC <bvarc@bvarc.org> wrote: One of the guys in KARS needs to test a few 811's, does anyone have a tester capable of testing these?
Thanks --jv na5d ________________________________________________ Brazos Valley Amateur Radio Club BVARC mailing list BVARC@bvarc.org http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org -- Rick Hiller e-mail: rickhiller73@gmail.comCell: 832-474-3713Physical: 9031 Troulon Drive Houston, TX 77036 ________________________________________________ Brazos Valley Amateur Radio Club BVARC mailing list BVARC@bvarc.org http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org ________________________________________________ Brazos Valley Amateur Radio Club BVARC mailing list BVARC@bvarc.org http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org
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