Testing radio tubes

[Deleted]

I got a tube tester from a local ham. I was testing tubes for the first time. I did the tubes from a Robyn T-240D. Anyway, I noticed some of the tubes required several seconds (like 15-30) to respond to the test button. Some were instantanious. Is this normal?

Also, they are well in the good area, but are around 65%. It that OK?

[Sandbagger]

Feb 16, 2009 22:24:51 GMT -5 @vinnies said:

I got a tube tester from a local ham. I was testing tubes for the first time. I did the tubes from a Robyn T-240D. Anyway, I noticed some of the tubes required several seconds (like 15-30) to respond to the test button. Some were instantaneous. Is this normal?

Also, they are well in the good area, but are around 65%. It that OK?

Tubes which take longer than normal to "come up to speed" are probably losing emission. Most tube testers have a "life" test where the filament voltage is dropped a bit and the emission should only drop off a few percent. If it drops precipitously, then the tube is just about shot. A tube which take a long time to come up will likely fail this test too.

Depending on the circuit, a 65% may be ok, but I feel better with at least 85%.

[BionicChicken]

I've got a Sencore Mighty Mite (forget the number) tube tester. It doesn't have a life test button but I have always dropped the filament voltage down one stage and it has done a pretty good job of telling the condition of tubes. On tubes like 8950's or M2057's I ususally drop two steps.
If a tube comes up slowly on emission I would agree it is probably weak. Let it go up as far as it will go and then drop the filament voltage on it. If it falls real fast I wouldn't want to use it unless it was the only one I had.

BC