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Daniel J. Nelson's Standard Vacuum Tubes¡ª¡ª
You may have experienced something
like this
before:
You have calibrated US military TV-7 series
tube testers, like £Ô£Ö¡Ý£·£Á¡¿£Õ¡¢£Ô£Ö¡Ý£·£Â¡¿£Õ¡¢£Ô£Ö¡Ý£·£Ã¡¿£Õ¡¢£Ô£Ö¡Ý£·£Ä¡¿£Õ
tube testers, strictly following the procedures
described in the maintenance manual. In spite
of that, at the final test stage, haven't
you found that while testing one and the
same vacuum tube, readings on different tube
testers are not exactly the same. On one
tube tester the reading is 55, on another
62, and still on the other 48?
Mr. Nelson is a world-famous doctor
of TV-7
Tube Testers living in Phoenix, Arizona,
USA.
I sent my inquiry about this point, and his
answer is:
> As you have discovered, tube testers
are not an exact instrument. I have
been
happy over the years to obtain
+- 6% between any two testers...
> One source of this variation is
that
the meters are not as linear as you
might
think. Also unit to unit variation
in the meters is as much as +- 6 on
the
scale. This means that you have to
calibrate
the TV-7 to reference
tubes as I have done instead of using
the
50V/10K source as the way to calibrate
the
units.
Therefore, the only method we can possibly
cope with this problem is to set your TV-7
tube tester's reading to that of Mr.Daniel
J. Nelson's Tube tester.
I asked him to sell me the following
tubes
he measured:
£Ò£á£î£ç£å¡¡£Á¡¡¡¡£µ£Ù£³¡¡¡¡¡¡£Ò£á£î£ç£å¡¡£Â¡¡£¶£Ì£¶¡¡¡¡¡¡£Ò£á£î£ç£å¡¡£Ã¡¡¡¡£±£²£Á£Ô£·¡¡¡¡¡¡£Ò£á£î£ç£å¡¡£Ä¡¡£¶£Á£Õ£¶
They are not brand-new tubes, but good enough
for my purpose, and Mr. Nelson sent
me the
tubes with his test-read values written
on
the tube cases like 42/25(6L6), 62/40,
60/40
(5Y3) 96/50,88/50 (12AT7) 86/58 (6AU6).
After
receiving his tubes, I adjusted my
TV-7C/U
tube tester manufactured by Stark Electronic Instruments to his settings.
It seems to be a matter of course that even
though Hickok is the original designer
of
the TV-7 series
tube testers, multitudes of manufacturers
assigned to produced TV-7 tube testers
in
the United States
or Canada, used slightly different parts,
the specifications of quality meters somewhat
different.
In the above pictures two TV-7D/U meters
produced £Ð£è£á£ó£ô£ò£ï£î are the same kind of 200
uA meters and are
reading the same current from 1.5V battery
with some resistor in series connection.
The same type, similar spec meter, but the
year manufactured is obviously different.
And you will see the
reading is about 8 degrees different on the
scale.
£Å£í£á£é£ì¡§£ã£æ£á£á£ø£´£°£¹¡÷£ê£ô£÷¡¥£ú£á£ñ¡¥£î£å¡¥£ê£ð
¡¡¡¡
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