HP Clock

Friday, January 6, 2012

Testing Dual Triodes with the Tek 575

I’ve been following a thread on the Tek Scopes forum 

discussing curve tracers with some interest since I recently acquired a second Tektronix 575.  I picked it up because it looked to be in good shape and it has the option that takes the collector voltage up to 400 volts.  A brief clean up and repair restored it to operating condition.  Here it is as purchased:

As you can see it was really dirty and dusty inside, and looks like it had been sitting unused for a very long time;

I’m lucky enough to have restored a Tektronix 570 tube tester that I actually still use at the office to check, test, and match tubes for various pieces of gear used by the audio engineers and mixers. Recently we were testing a pre amp that used a large number of 6DJ8 dual triodes. 

Inspired by the TekScopes thread and the tedium of patching on the 570 I decided to make a test fixture for the newly refurbished 575.  I have to say it works great and is perfect for quickly testing a large variety of dual triodes since many of them have the same pin out.  Here is the inside of the dual triode test fixture being wired;

Here is a picture of the completed tester:

And finally here is the tester being used to go through a box of used dual triodes:

I had to laugh, because when I brought in the text fixture and proudly showed it off to one of my colleagues, he asked what a 575 looked like.  No problem.  I went to Google images and one of the top search results was the image on this site.  (scroll down al little.)

So….not an original concept, and they are even testing the same tube.  

There is a PDF in works that I will post for anyone that want to try this.  That said, I will offer the usual disclaimer. Some of the circuits described on this site use or generate potentially lethal electric currents and voltages, and if not treated with care, respect and intelligence, they can result in fatal injury. If you use the information on this site to kill yourself, your friends, family members, acquaintances, total strangers, pets, electronic devices or burn down your house, it is not my problem.