KT-150 Tubes- Push Farther or Replace?

invalid.

I'm saying, let go of perfection, go for basic knowledge, I think most people will NOT spend for a big/better one.

IF it just finds shorts, not knowing and continuing using them can be quite harmful to your transformer, amp, 

If they appear to work, like an inexpensive sound meter: they do not need to be accurately calibrated. They will be relatively accurate regarding strength as well as find shorts.

If meter shows bad or weak, even if off a bit, relace them, and test the new ones. the results tell you about your tester, and if they are ’matched’ the meter, if not calibrated, will still show you if they are closely matched.

Better than being helpless, in the dark.

@elliottbnewcombjr

We’re saying it’s not good data from those testers. OP sees a pair of KT tubes not holding bias in his amp, and knows the hours are in excess of 2000 - and that alone is far better quality data than an emissions tester will tell you. It’s not adding any information, and in fact might make one draw the wrong conclusions (i.e. that a bad tube is still good).

If you buy a grab bag of old unknown tubes and want to quickly screen out the dead-dead ones - then that’s maybe a use case for these testers.

A tester is not going to predict an oncoming short. Nothing can. Staying within tube usage guidelines and being an attentive user (check bias occasionally) is how you reduce the chances. If it happens, you can only hope the amp's protection circuitry kicks in in time to prevent board damage. 

The problem with some of the cheap emissions testers is they only run the tube at 30 volts, some of the better ones maybe up to 150 volts, the kt150 needs to be tested at a higher voltage. The best way to test them is in circuit. 

@mulveling is a wise man listen to him. Enjoy the music

Agree with @invalid, some circuits are running up to 600V plate voltage at about 80 - 85 mA current per tube. I ran my KT150s in the 50ma range per tube and they still sound great. Some of the diy folks were talking about this a while back, getting up to 4,000 hours without issue, yet noting some of the older tubes had getters fading faster than more recent production past few years. Best to follow the rec above "best way to test is in the circuit". Keep a close eye on this 2nd set for a while and check how quickly they stabilize at their first bias set point. Best of luck.