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How to test the vacuum on a vacuum tube?

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LAN_403

radiotech

Thu Mar 04 2010, 10:34PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

looking at the pin designations 1 - screen 8 - cathode. just a wild card guess- could you have exchanged cathode for screen-by somehow counting in the opposite direction? (easy to do w/o a )socket.

Conundrum

Sat Mar 06 2010, 02:57PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

the other "if all else fails" revival technique mentioned in Electronics World, is to very carefully heat the tube in a fan oven NOT grill! to around 120-150 Celsius for about 12 hours max. Allow to cool and retest, it may improve things but won't help with an up to air tube.

Also another thought, if the base got damp then conductive paths may have formed, in which case the oven trick could help.

could also be worth operating the tube with correct heater voltage for a day and retest...

regards, -A

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