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Old 04-03-2017, 06:06 PM
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dtvmcdonald dtvmcdonald is offline
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Join Date: Nov 2012
Posts: 855
I got my CR-70 today. If it is working correctly, only one out all my non-electrostatic
guns is actually good: the blue gun of my 15GP22 tests perfect. Its green gun
is a bit lacking in cutoff but emission is fine. My 10BP4 and 12LP4 both test
bad in cutoff and the 12LP4 is also a bit poor in emission. The red gun of the
15GP22 is abysmal in cutoff but about 3/4 of the way to good in emission.
This proves that the tube is indeed bad bad bad.

I'm surprised that the 12LP4 sold to me by the ETF tests poor to bad.
I tested both 5BP4s I have that are not in a TV. I don't know
what the cutoff is supposed to be, so I estimated it at 8 volts from the
spec that the "visual" cutoff should be 1 to 3% of the G2 voltage
(set at 415 v) . This proved roughly correct for both tubes,
which both tested borderline emission, though the ratio was
what I expected from use in my TT-5.

Last edited by dtvmcdonald; 04-03-2017 at 06:09 PM.
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