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Old 23rd Jan 2011, 1:19 am   #5
paulsherwin
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Join Date: Jun 2003
Location: Oxford, UK
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Default Re: EM84 tube - pinout and spec?

All magic eyes are essentially voltage indicators. If you apply heater voltage and some HT, they will show the voltage applied to the grid.

The EM84 is unusual in that it has the phosphor applied directly to the glass side of the envelope rather than to an internal metal surface. Because of this it is very accurate, and was actually used in calibrated form in some test equipment. It was the standard record level indicator in most 1960s domestic tape recorders.
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