Author Topic: Tubes  (Read 3254 times)

624Magnificent

  • Hero Member
  • *****
  • Posts: 525
  • Western Maine
    • View Profile
Tubes
« on: July 13, 2015, 08:26:10 AM »
Ok so I have a reasonable understanding of what a tube is and some sense of what "rectifier", "preamp", and "amp" tubes do. I see a lot of posts where I get the sense that a few members have much more knowledge than the rest of us. I thought a post specifically about tubes might be helpful to many of us.

Could those of you with "guru" knowledge talk about the following things;

  • Types of tubes and their uses.
    Symptoms of failed, failing or weak tubes.
    Ways to test evaluate tubes with tube testers, multimeters, or just good horse sense.
    Tubes to watch out for or that are particularly problematic or should be just be replaced period.

Tom

spiritofradio

  • Sr. Member
  • ****
  • Posts: 337
  • Richmond, Va
    • View Profile
Re: Tubes
« Reply #1 on: July 13, 2015, 09:17:37 AM »
Tube testing seems to be a science all its own. I have never replaced a tube unless.it was broken.  visually I check the silver stuff on top of the tube to see if it hasnt been burned away, but other than that.... I have found a local fella that will test them for me for a buck a tube. I might only do this for my daily driver or if im working on a really special set for someone.
I wish there was a good way but i dont see myself buying a tester. I wouldnt know what to do with it...
~~~and did you exchange.......
a 'walk-on' part in a war.....
for a lead role, in a cage?~~~

Consoleman

  • Hero Member
  • *****
  • Posts: 704
  • Southeastern PA
    • View Profile
Re: Tubes
« Reply #2 on: July 13, 2015, 09:42:06 AM »
This is a good place to start - the National Valve Museum. http://www.r-type.org/index.htm. There are links for new visitors on the upper right that will give you all the info you need and then some.

If you're going to run tube gear then you need to either invest in a tube checker/tester or find someone near you who has one. There's no other good way to tell what's going on with one. They're quite easy to use.

Mark

TC Chris

  • Hero Member
  • *****
  • Posts: 881
    • View Profile
Re: Tubes
« Reply #3 on: July 14, 2015, 08:49:20 PM »
There are two types of tube testers.  I have an old Heathkit that I built that is an emission tester--it tests the total emission of the tube, using all the grids and plate as a plate.  You can also test to see if there are any sorts between elements or  if the tube is gassy. (Interestingly, I have a Knight-kit tube tester that is basically identical to the Heath--don't know if one company built it for the other, or if both companies purchased things from a third one).

The better kind of tester is a transconductance tester.  It tests the tube as though it were in service, with grid bias and all.  It's a better way of matching tubes.  I don't have one of those.

Chris Campbell

Larry H

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 2664
  • Little Rock, Arkansas
    • View Profile
Re: Tubes
« Reply #4 on: July 14, 2015, 09:21:06 PM »
A simple Heathkit tube tester that tests for emissions and shorts is all you need.  I got lucky and got one on eBay about 8 years ago for $20.  Mine is a Heathkit TC1.  It works very well.
--Larry

Consoleman

  • Hero Member
  • *****
  • Posts: 704
  • Southeastern PA
    • View Profile
Re: Tubes
« Reply #5 on: July 15, 2015, 07:32:14 AM »
Mine is a Sencore Mighty-Mite II. Does everything I need it to do.

Mark

eman

  • Jr. Member
  • **
  • Posts: 89
    • View Profile
Re: Tubes
« Reply #6 on: July 20, 2015, 04:56:26 PM »
I have a Precision 10-12 and it is not an emissions or Mutual conductance:

"""Precision called the testing method “Electronamic”, and they argued that is “more than just Mutual Conductance.”  Precision wrote a two-page article explaining the Electronamic test method, which you can download [HERE].  While it would be heresy to argue that Electronamic is “more” than Hickok’s mutual conductance, I would suggest that the test method is extremely reliable.  The Electronamic method is similar to the Jackson 648 test method.  I find that the tube test results from the Precision 10-series usually track quite close to Hickok test results.  The Electronamic test method uses all AC voltages."""


http://tubesound.com/wp-content/uploads/2009/09/electronamic.pdf


E
T

Pat L

  • Founder of the Board
  • Administrator
  • Hero Member
  • *****
  • Posts: 1429
  • Southeastern Wisconsin
    • View Profile
Re: Tubes
« Reply #7 on: July 20, 2015, 05:11:37 PM »
I use a Jackson 648A myself and love it. It provides excellent results equal to the finest Hickok tester. I sold my last Hickok for $400 and kept the Jackson that I only have $100 in. That's putting my money where my mouth is.  ;)

Larry H

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 2664
  • Little Rock, Arkansas
    • View Profile
Re: Tubes
« Reply #8 on: July 20, 2015, 06:08:12 PM »
I had a Hickok also and it took forever to test one tube.  I didn't like it either, and sold mine to another moderator on ARF.  My Heathkit that I paid $20 for does just fine.
--Larry

danrclem

  • Sr. Member
  • ****
  • Posts: 345
    • View Profile
Re: Tubes
« Reply #9 on: July 20, 2015, 11:15:12 PM »
I've got a Triplett 3444A but I haven't used it yet. 

revolverone

  • Full Member
  • ***
  • Posts: 159
    • View Profile
Re: Tubes
« Reply #10 on: July 21, 2015, 08:24:08 AM »
I love my Mercury Tube tester.  I had a previous one that finally bit the dust, but I loved it because it was very simple to use.  When I went to replace it, I bought another Mercury.  The top cover of this one is pretty worn out, but it works great.  I got a good deal on it :)

Motorola Minion

  • Hero Member
  • *****
  • Posts: 620
  • Southern Pennsylvania
    • View Profile
Re: Tubes
« Reply #11 on: July 22, 2015, 03:13:41 PM »
I have a Weston 798 "mutual conductance" tester that is very good for all tubes made up to about 1952.
It was once owned by DuPont corp. probably to test industrial tubes.

My EICO 635 is a simple emission tester similar to the Heathkits and was a kit I built in 1977 for the tubes the Weston had no sockets or chart for.
Its fast but the best test is the set itself and confirmed by subbing in a new tube. :) 

 
Tubes - Magical - Tubes

Dave

AMP82-01-00

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1006
  • San Antonio Texas
    • View Profile
Re: Tubes
« Reply #12 on: July 28, 2015, 10:32:40 PM »
I have a sencore mighty mite TC162 it was new in the box and works perfectly for what I need. Most Hickoks are thought to be the best.
David        "If it ain't interesting, its really just boring"

Motorola Minion

  • Hero Member
  • *****
  • Posts: 620
  • Southern Pennsylvania
    • View Profile
Re: Tubes
« Reply #13 on: May 10, 2016, 04:09:25 PM »
Pardon the bump in this topic. I've been working on tubed equipment using 6BQ5/EL84 and need to test tubes as routine.

I found a huge difference between my EICO 635, which is a simple emission tester and my Weston 798, a very old mutual trans-conductance tester. The Weston has a 9-pin socket but being from 1947, only lists 12AT7/AU/AV/AX7 on the chart. I tried to figure out how to test the 6BQ5 but the 9-pin socket is dedicated to the dual-triode tubes.

Then I had an idea that the 6V6 and 6L6 were close enough so I made an octal to noval adapter from a tube base and 9-pin molded noval socket. I then approximated the sensitivity, bias and plate load settings.

The differing results were remarkable. Out of 18 tubes, all used to some extent, the EICO failed not a single one. No shorts and only 1 with low emission. The "good" results varied over 10% of the bad-?-good scale. Not much help, right? These old used tubes were from US, GB, Holland, Austria and Japan.

Then I tested all 18 6BQ5's on the Weston and they were ALL over the scale. I was able to weed out 3 very weak (as shown), 2 weak  and 13 good to excellent. A new Sylvania tested at 10000 gM.

Tubes - Magical - Tubes

Dave

Harbourmaster

  • Hero Member
  • *****
  • Posts: 2216
  • Long Beach, CA 90808
    • View Profile
Re: Tubes
« Reply #14 on: May 10, 2016, 07:49:44 PM »
I don't own a tube tester... there are plenty of other radio guys around here that have them and if I need to test tubes I just go to there place and do em.
-- Aloha, Ken

No Console Left Behind!