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Old 11th Jan 2015, 9:45 am   #39
Mike. Watterson
Heptode
 
Join Date: Dec 2014
Location: Limerick, Ireland.
Posts: 901
Default Re: Rejuvenating Magic eye Valves?

The older type do use a short life phosphor. The DM160 indicator and DM70/71 is phosphor on metal but about as long life as a modern VFD (which is similar technology to DM70 but in a planar package and still made). There are three types available as cheap NOS from China / ex USSR countries which can replace many:
Octal
Noval angel wing
Noval bar
I've used all three. The socket needs rewired or an adaptor fitted. If supply is 4V then you can use a Schottky Diode bridge ( 4 x 1N5819 or similar) and capacitor to get just over 5V, which is great but should work.

Some useful articles
Life http://www.radiomuseum.org/forum/lif...magic_eye.html
Overview and the three Russian / Chinese types http://www.radiomuseum.org/forum/mag..._patterns.html
More on the three cheap NOS types
http://www.radiomuseum.org/forum/magic_eye.html
Details on replacing EM34
http://www.radiomuseum.org/forum/rep..._the_6e5c.html
The various 6 pin and 8 pin side connect can be replaced too with a suitable adaptor.
EM80
http://www.radiomuseum.org/forum/how...4_or_em85.html

Article on ageing and rejuvenation. Increasing Anode voltage and decreasing current helps, except the indicator part grid is usually tied to cathode internally, so the only way to decrease current is to thermal emission limit by reducing heater.
http://www.radiomuseum.org/forum/lig...eye_tubes.html


I have some nearly "blank" EM34, I will try regular oven for overnight. The Microwave is too hard to control. With a regular oven the heat can only travel on the pins. A contactless IR themometer and infrared lamp or grill might be a good solution.
I've had an EM84 / EM87 type with a short that develops when it heats up. Otherwise the Noval ones are much longer life as are DM70 and DM71
http://www.radiomuseum.org/forum/dm70_operation.html

(I wrote some of the articles, so apologies if I made errors)
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