Testing a dual rectifier valve

[Paul]

My reason for building a uTester 3 was that I was given a couple of boxes of valves to sell for a friend and a local ham radio club.  

I'm quite happy with testing triodes and pentodes and comparing them to the data in the AVO valve lists.  However, I am a bit stuck when in comes to testing rectifiers.

In particular, I have a Cossor 53KU.  http://www.r-type.org/pdfs/gz37.pdf

This needs 5v at 2.8A for the heater so I will need an external supply for the heater.  However, how do I set the VA to and what constitutes good?  The AVO valve lists just indicate a current of 120mA but with no indication of voltage.

Apologies if this is a very noddy question.

Paul

[Henning Oelkers]

Hi, Paul,

Testing a rectifier with μTracer only works with very low voltages, i usually use 10 or 20 Volts.

As this is a double rectifier you easily can compare both systems, and see, if one is weak.

Its difficult to find, if a rectifier is weak on both systems. Therefore i use a different Method for Diodes and rectifiers, using a scope, a transformer, and a resistor. 

Just give it a try, and keep in mind, that a diode is the same as a full open triode, giving you a high current at low anode voltage.

Best Regards, Henning

Von meinem iPad gesendet

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[Paul]

Thanks.

I managed to test a couple of rectifiers successfully today.  I had to use an external power supply but was able to replicate the voltage drop for a given Ia current given in the data sheet for the valves.  Well, almost, both were slightly more than the 200mA maximum current from the µTester but I was able to extrapolate.

Paul