There were four 811's in the RCA transmitter I used to babysit. That
thing was a brick.
The Harris daytime transmitter was a lot less reliable.
On 7/30/20 4:15 PM, john Parmalee via BVARC wrote:
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 WI2XLJ
In a message dated 7/29/2020 2:15:55 PM Central Standard Time,
[email protected] 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
<[email protected] <mailto:[email protected]>> 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
<http://www.radiotechnika.hu/images/811A.pdf>
My e-mail is:
[email protected] <mailto:[email protected]>
73
John, KI5HOC
On Tue, Jul 28, 2020 at 9:42 PM Rick Hiller
<[email protected] <mailto:[email protected]>> 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
<[email protected] <mailto:[email protected]>> 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
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Rick Hiller
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*/ Houston, TX 77036/*
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________________________________________________
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Jonathan Guthrie
ARS KA8KPN
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