Hello Rick:
It is quite easy to build a tube tester for particular tubes. I just built
one for the old 211 triodes. I put it in an old wooden case from some
obsolete medical equipment and it looks gorgeous. Many of the old radio
books from the 1930's outline how to do it.
In the simplest form, you can build an emission tester. All you need is a
tube socket, a filament transformer, a vom and a 9 volt battery. Connect
all the grids together and to the filament, connect the - side of the
battery to the filament and the + side to the postive lead of the vom (with
scale on microamps). Then connect the - side of the meter to the plate.
This will tell you emission. Crude but often accurate enough to compare
tubes.
For a more exotic tester, you can use a 250 volt or so plate voltage with
ma to monitor plate voltage. Have an adjustable - grid voltage of 0 to
-100 volts (a simple pot is fine since there is no current being drawn.
Use 100 volts on the screen (no regulation needed). Then monitor plate
current with changes in grid voltage. Measure grid voltage with a dvm.
You can calculate gm of the tube by monitoring the changes in plate current
with changes in grid voltage. If you want real accuracy, you would
regulate the dc screen and plate voltages. But, for amateur use, being
close is the same as perfect.
If you have have nothing better to do, you can monitor screen current and
grid current, build protection circuits so a shorted element will not bend
the meter needle. Soon, you will be able to market the Rick Cole tube
tester. You can market it to cb operators and audiophools for big bucks
and use the profit to support you ham radio hobby.
Good luck, Colin K7FM
> [Original Message]
> From: RICK COLE <vk3ym@iprimus.com.au>
> To: <Amps@contesting.com>
To: <amps@contesting.com>
> Date: 8/20/03 7:34:24 AM
> Subject: [Amps] what tube tester!!!
>
> I am looking to buy a tube tester but there is very little available =
> here in Australia so need some advice..
> My main use.. 90%..would be for testing sweep tubes and others such as =
> 6146 etc from early Kenwood, Yaesu and similar types.
> Any advice would be appreciated.
> Regards Rick
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