|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
63.246.183.223
In Reply to: RE: testing a 6L6GC in my EICO HF87? posted by DAK on August 03, 2014 at 10:34:36
If the tubes appear stable, I take the measurement at 10-15 minutes after power-on. However, many of the tubes I test are more than 30 years old. Even when the gettering looks good, they're sometimes gassy. In that case, I'll start them at a lower voltage to prevent thermal runaway, gradually raising the amp to full voltage (about +400V). This sometimes takes an hour or more, and the tubes have to be monitored all along the way. Once they're at full voltage, I let them cook for about another hour to hopefully burn off any remaining residual gas. Any tube that can't be raised to full voltage with an acceptable current draw, or that remains unstable after the full-voltage cook, goes into the trash.
--------------------------
Buy Chinese. Bury freedom.
Follow Ups:
Talking about cooking tubes, I remember reading somewhere about "baking" your tubes in an oven over a period of time to have the out gases adsorbed by the getters. I forgot at what temperature and the duration of baking.
I've heard of that too. Sounds a little hokey, but who knows? I still remember a friend in the '60s telling me dud crystal microphones could be rejuvenated with a stint in the freezer. :)
--------------------------
Buy Chinese. Bury freedom.
I am through testing. I did 12 RCA and they all tested ok, no runaways. I can now match them up for push pull operation. thanx for the support, regards, Dak
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: