SImple Valve (Tube) Tester

Introduction: SImple Valve (Tube) Tester

A valve tester is nothing more than a set of adjustable calibrated power supplies, a meter to measure to current and a set of sockets into which the valve under test can be inserted.  However when I started to look for a second valve tester I found them incredibly expensive, I therefore decided to make one.

The valve tester shown here has an adjustable HT supply (upto 300V), an adjustable negative supply for grid bias (upto -50V) and a  heater supply.

The HT supply is just a simple cathode follower, based on a circuit from Radio Constructor by G A French.  Initially I was going to have a switch on the voltmeter to monitor grid voltage as well as anode voltage but in practice it was easier to use my DVM.

Step 1: Notes and Pictures

I used valve data for an AVO valve tester when testing valves, any valves that required a heater voltage other than 6.3V I used a seperate power supply.  The EL81 is also overrun with some valves, this has not caused a problem.  In use I manged to damage the milliammeter due to faulty valve, I plan to put a diode across the movement in future to help prevent this.  I also found that the odd valve would oscillate at high frequency.

1 Person Made This Project!


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Question 9 months ago on Introduction

A question: is it correct that de 6.3V filament of the EL 81 is connected in the high voltage circuit? Shouldn't that be the cathode only...? Thanks for your comment in advance. Brgds Herman


1 year ago

Thank you for publishing this. It's been a great project so far, and I'm nearly done. I found and bought a University tester shortly after I started this, but this is much nicer. it will be interesting to compare the two. The University uses a completely different approach.

valve tester.jpg

3 years ago on Introduction

Thank you very much! Here is finally a solution that deals with EL81's problem in PSU-designs that heater-cthode voltage (Vh-k) should not exceed 100V. Love these old articles, do you recall in which copy of Radio Constructor it was published?