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EM34 function

Jacob Roschy Martin Renz Ernst Erb Bernhard Nagel Eilert Menke 
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Forum » Valves / tubes - Semiconductors » VALVES/TUBES / SEMICONDUCTORS in RADIOMUSEUM » EM34 function
Philip Navarrete
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25.Oct.06 23:37

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Just what is the EM34 Eye supposed to do? My EM34 does not give the eye indication at all in FM. It's dark and blank. From what I remember the eye is supposed to open and close as stations are changed. Could I have a bad EM34?

Philip Navarrete


Thread moved to tube

This article was edited 26.Oct.06 08:28 by Eilert Menke .

Thomas Albrecht
Thomas Albrecht
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26.Oct.06 00:28

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The EM34 is a dual-action eye tube.  It should glow brightly, with a dark wedge at both the top and bottom of the face.  One of the two wedges is more sensitive than the other.  For example, on a weak station, only the more sensitive wedge changes width.  On a very strong station, the sensitive wedge is saturated, and the less sensitive shows some width change.

If the tube doesn't glow at all, check the plate and grid voltages to make sure there isn't a problem in the surrounding circuitry.  Unfortunately, it is not uncommon to find very dark or completely dark eye tubes.  Most used ones have low emission.  The lifetime of these tubes is only 1000 hours or so.  If the radio was used frequently, the eye tube could easily have worn out in the past.  Since the radio still functions fine without a working eye tube, many radio owners never bothered to replace the eye tube.

Best regards,


Philip Navarrete
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26.Oct.06 13:59

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Thanks Tom I'll check the voltages.