I replaced a bad 6U5 tuning eye with a good one and it works, but it's so dim I can hardly see it. Can someone tell me what causes that? I'm restoring a nice old Packard-Bell radio and the schematic I printed from NA doesn't even show the tuning eye, let alone the voltages for any of the other tubes.

Dick: Was the replacement tube used? These tubes grow dim with use due to depletion of the phosphors? I take it that the eye opens and closes as it should?

Once an eye tube goes dim, there doesn't seem to be any way to rejuventate it. I've heard of trying to jack up the plate voltage to it, but that would get complicated and may not work anyway.
Doug

:I replaced a bad 6U5 tuning eye with a good one and it works, but it's so dim I can hardly see it. Can someone tell me what causes that? I'm restoring a nice old Packard-Bell radio and the schematic I printed from NA doesn't even show the tuning eye, let alone the voltages for any of the other tubes.

Dick

Only need filament voltage between pin #2 and #6, 6 volts. Cathode grounded, pin #5. About 250 volts on the target, pin #4. That's all to see the green glow. If target voltage is low green will be weak. A new tube should show green down to 100 volts or so.

Are you sure your eye tube is new?

Norm

:I replaced a bad 6U5 tuning eye with a good one and it works, but it's so dim I can hardly see it. Can someone tell me what causes that? I'm restoring a nice old Packard-Bell radio and the schematic I printed from NA doesn't even show the tuning eye, let alone the voltages for any of the other tubes.

I bought 2 used tubes and both test OK on my TV-7, but no green in the set so I suspect the voltages are not right and will check that. The tube I replaced shows no green in the tester. Thanks for the voltages.
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::I replaced a bad 6U5 tuning eye with a good one and it works, but it's so dim I can hardly see it. Can someone tell me what causes that? I'm restoring a nice old Packard-Bell radio and the schematic I printed from NA doesn't even show the tuning eye, let alone the voltages for any of the other tubes.