Hi everyone
How can I create a simple circuit to test a directy heater cathode rectifier diode in working conditions?
How can I create a simple circuit to test a directy heater cathode rectifier diode in working conditions?
I would try to recreate the test conditions listed in the data sheet. Often that's something like a DC source provided to the anode with the cathode connected to ground through a constant current source. You then verify that the voltage drop across the diode is reasonable given the test conditions.
Second best would be to replace the CCS with a resistor.
Tom
Second best would be to replace the CCS with a resistor.
Tom
Simplest would be testing in a suitable amp.
Otherwise you'll need an adjustable high power load.
Otherwise you'll need an adjustable high power load.
The GZ34 uses indirect heating while a 5U4 is directly heated.
What testing difference do you mean?
It's just as simple with those that have direct heating. You just need a floating power supply that can provide the voltage needed for the filament. You also need to make sure that this floating supply can be allowed to float at the full anode voltage.
Tom
I am referring to the filament power supply which for the GZ34 seems to be AC only.
Strange that instead in the GE datasheet of the 5AR4 which should be identical the CC is also included.
GZ34 and 5AR4 are equivalent.
I can't think of a reason why you couldn't use DC heating with the GZ34.
But why would you want to do that?
Don't forget that the heater supply is floating on the output voltage of several hundred volts, so needs to be well isolated.
That's much easier to achieve with AC.
I can't think of a reason why you couldn't use DC heating with the GZ34.
But why would you want to do that?
Don't forget that the heater supply is floating on the output voltage of several hundred volts, so needs to be well isolated.
That's much easier to achieve with AC.
One man's simple is another man's Rubik's Cube. What test conditions do you want to place the rectifier under? Maximums"? Do you want to do more than one type of tube? Do you want adjustability of the power source and or adjustability of the loads? You are not going to get that ''simple'' circuit unless it is for a simple test that is limited in its scope. ''Working conditions '' can be a very wide specification.
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You could test a few practical aspects at close to low voltage. For example, power the rectifier heater at nominal Vac with a suitable supply. Then connect a DC power supply from anode to cathode and measure the current at some set dc voltages such as 12V, 24V, 36V. That would be easy if you had a benchtop power supply with meters, but can be a bit cruder using 12V batteries and a current sense resistor or in-line current meter. Each anode should pass about the same current as the other, perhaps to within about a difference of 90-110%, otherwise that could indicate a noticeable unbalance that may exhibit itself as mains frequency ripple. Lowering the heater voltage by say 10% can also indicate aging/health of cathode.
I'd suggest you would need a 'Megger' type insulation resistance meter to check the leakage from anode to cathode at say 1kVdc. That type of testing is not commonly done, as not everyone has a suitable IR meter. I did that kind of testing on a large batch of 5U4/5AS4 in section 7 of linked doc: https://www.dalmura.com.au/static/Power supply issues for tube amps.pdf
I'd suggest you would need a 'Megger' type insulation resistance meter to check the leakage from anode to cathode at say 1kVdc. That type of testing is not commonly done, as not everyone has a suitable IR meter. I did that kind of testing on a large batch of 5U4/5AS4 in section 7 of linked doc: https://www.dalmura.com.au/static/Power supply issues for tube amps.pdf
Define working conditions.
Are you wanting to measure Forward voltage drop?
You can set up a simple half-wave rig with a suitable resistive load to simulate something close to your 'working conditions' and measure how it compares to a 1N4007 in the same circuit. 1N4007 has a forward voltage drop is about 0.7V in the case of forward current 1A, so for 100mA it will be 0.07V, etc. (almost nothing) By comparison you can determine your forward drop and see how 'efficient' different diodes are.
Depending on the voltages you are testing for, I would use a variac to bring the voltage up slowly - especially if it is a diode that you are unsure of.
Or are you just wanting to test for shorts?
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