Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Diagnostic & Test Equipment

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #1  
Old 01-24-2018, 10:16 AM
Winky Dink's Avatar
Winky Dink Winky Dink is offline
VideoKarma Member
 
Join Date: Apr 2010
Location: Meridian, Idaho.
Posts: 506
Zombie Tube Saga

In the course of my most recent project, the radio under test started sounding weird, then went silent. I found an accidental short which apparently killed my only 2A5. I tested the tube and found all to be OK except it showed zero transconductance. I rechecked the settings, retested, then tested on an emissions tester. Same result. Zero emissions. So I set it aside.

In the next few days I acquired three used 2A5's. Two tested OK, but the third showed a heater/cathode short on the transconductance tester. Retest after a five-minute warm up gave the same result on both testers. So I set it aside.

Four days, before tossing the cathode/heater short tube, I decided to check it again. I put in the tester, turned it on, and forgot about it. A hour later I looked at it, and it showed no leak, no short, and excellent transconductance. So, it was a self-healing tube. Probably got something on the cathode or heater which took a while to burn off.

Then I thought, what the heck, I'll retest the dead tube. Son of a gun, it was normal too. This was good fortune, but also eerie. How did it come back from the dead?



Now that it's a Zombie Tube, how do I keep my other tubes safe?
__________________
Winky Dink
Damn the patina,
Full speed ahead!
Reply With Quote
  #2  
Old 01-24-2018, 12:01 PM
N2IXK's Avatar
N2IXK N2IXK is offline
Technohippie
 
Join Date: Apr 2011
Location: Sittin' on the "Group W" bench...
Posts: 766
A tube with low emission coming back to life after being heated for a while is quite common. It does seem to be some kind of contamination being cleaned off a long-dormant cathode coating. This is especially common with CRTs.

The H-K short going away is more unusual, and I would be worried about it coming back. Try banging the tube around a bit while testing to see if you have an intermittent.
Reply With Quote
  #3  
Old 01-24-2018, 12:15 PM
Winky Dink's Avatar
Winky Dink Winky Dink is offline
VideoKarma Member
 
Join Date: Apr 2010
Location: Meridian, Idaho.
Posts: 506
I do rattle tubes when testing them. These two seemed OK, but I put them away with a note about their history.
__________________
Winky Dink
Damn the patina,
Full speed ahead!
Reply With Quote
  #4  
Old 01-24-2018, 09:12 PM
MadMan's Avatar
MadMan MadMan is offline
'A Disgusting Brony'
 
Join Date: Oct 2016
Location: Chicago
Posts: 654
Just keep it away from any fresh brains, you should be fine.
Reply With Quote
  #5  
Old 01-24-2018, 09:41 PM
dieseljeep dieseljeep is offline
VideoKarma Member
 
Join Date: Jul 2010
Posts: 6,285
Quote:
Originally Posted by MadMan View Post
Just keep it away from any fresh brains, you should be fine.
I'm trying to remember, if Zombies are the ones that don't have a reflection.
Good old days of the Friday evening horror movies on TV.
Reply With Quote
Audiokarma
  #6  
Old 01-24-2018, 10:03 PM
Popester's Avatar
Popester Popester is offline
VideoKarma Member
 
Join Date: May 2012
Location: Lakewood, CO
Posts: 103
It was Dracula that wouldn't have a reflection from a mirror. Also Dracula hissed and howled when a crucifix was shown in his face lol.
__________________
Sony Trinitron is my favorite brand.
My wish list:
Sony KV-1210U
Sony KV-5000
Sony 8-301W

Last edited by Popester; 01-24-2018 at 10:04 PM. Reason: Spelling
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 10:39 PM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
ęCopyright 2012 VideoKarma.org, All rights reserved.