Tubes Asylum

RE: 6550/KT88. Your 539C is not going to be able to put 85 watts on the plate (nt)

52.119.121.37

6bq5

In Reply to: RE: 6550/KT88. Your 539C is not going to be able to put 85 watts on the plate (nt) posted by Chip647 on November 18, 2024 at 06:20:26

Agreed!
any of the NEW "KT" series can not be adequately tested on testers that were built 25+ years before the tubes were developed...
Happy Listening

Follow Ups:

RE: 6550/KT88. Your 539C is not going to be able to put 85 watts on the plate (nt) - Jim McShane 10:30:45 11/19/24 (1)
Just an excerpt from my FAQ here on the Tubes Asylum:

Most tube testers do not test power or other high voltage/high current tubes at a high enough voltage to be very meaningful. And matching of current is pretty much out of the question for all but the few "lab grade" testers that can apply high voltages at reasonable current levels to the tube. What your tube tester says with 150 volts on the plate will differ significantly from what my rig says at 465 volts! ... Remember - a tube's test results depends on the conditions under which it is tested!

So even if you have a good mutual conductance tester there are significant limitations to the testing you can do with it. And those limitations are even more significant when you have tubes like the KT170 that are higher power/current/voltage handling than the KT88/6550 tubes that were pretty much the highest rated power tubes of the day back when most vintage testers were developed.

My guess is (I have not tried it) you can get some info testing it using the KT88 or 6550 settings as long as the tester can provide adequate heater current. One way to determine that is to see if your tester will test a 6AS7 or 6080 - both draw more heater current than the KT170.
- Tube Problems That Aren't Tube Problems (Open in New Window)
- RE: 6550/KT88. Your 539C is not going to be able to put 85 watts on the plate (nt) - John PA 07:20:06 11/20/24 (0)
  I agree with all of this. It's been one frustrating thing about the tube testers that I have is that they only use 150 V on the plates. Having said this, I do have some tubes that have been tested at full voltage and then I checked them on my 539C and current draw puts them in as basically matching and I do get an idea of how the tube is doing, but absolutely totally agree that using the right plate voltage is really the only way to go for sure.
  
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