[Hallicrafters] Testing tubes

[Barrie Smith]

Attempting to discover why an old Luxman tube-preamplifier didn't sound too
good, I drug out the Hickok Cardmatic tube-tester this morning.

I noticed that 6 of the 7 12AX7s tested off-scale (to the right, above 100).
New 12AX7s that I tested ran from 80 to 90 on the scale.

Is there a problem with an off-scale reading?

There was no indication of leakage or gas in any of the tubes.

Also, all of the tubes that tested off-scale had another characteristic:
Upon powering them up in the tester, the wires in the base that evidently
connect to the cathode lit up bright red to almost white for a short period
of time, perhaps a second or two.

The new tubes that I tested did not exhibit that characteristic.

Any thoughts on this subject?

73, Barrie, W7ALW