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Old 10th August 2008, 03:25 AM   #1
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Default Tube tester and PSUD II questions

Two unrelated (and possibly dumb...) questions:

Is there a way to use my Eico 625 tube tester to test tubes that are not on the roll chart like EL34's, 6550's, EL84's, etc? Am I wasting my time using this tester? I am aware that it is not a transconductance tester but i am hoping for some basic functionality tests of some used tubes. Can I get the req'd parameters off of the tube data sheet and set the dials of the tester to these values?

How does one perform a "step input" function in PSUD II? I'm assuming this is done to look for ringing, underdamped/overdamped response, etc...Is the objective to get close to critical damping when performing this test?

I understand how to change component values and different PS modules RC/LC, etc and add modules, and run the simulation for 1000 ms, 2000 ms, etc looking at various voltages and currents.
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Old 10th August 2008, 03:57 AM   #2
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Default Re: Tube tester and PSUD II questions

Quote:
Originally posted by boywonder

Is there a way to use my Eico 625 tube tester to test tubes that are not on the roll chart like EL34's, 6550's, EL84's, etc? Am I wasting my time using this tester?
Try looking for 6CA7 for the EL34 and 6BQ5 for the EL84. There is no good equivalent for the 6550 except KT88 which probably isn't on the list either. But the socket connections are the same as a 6L6. Try testing a known good 6550 as a 6L6 and adjusting the shunt control for an upscale reading. This is a DC emission tester so the readings are not good for matching but may help weed out the definitely bad from the possibly good. Be sure to keep your line adjust set right.

Victor
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Old 10th August 2008, 04:05 AM   #3
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Default Re: Tube tester and PSUD II questions

Quote:
Originally posted by boywonder
How does one perform a "step input" function in PSUD II? I'm assuming this is done to look for ringing, underdamped/overdamped response, etc...Is the objective to get close to critical damping when performing this test?

Simulate the load as a current source, not a resistor. Change its properties so that you have the approximate current as expected under loaded conditions. The enter a stepped current to say 5% more at a time of maybe 3.1 seconds.

When you simulate, you will want to watch the window of maybe 500 msec starting at 3 seconds. That way, you see the output just before the step change, and afterwards. In general, yes, you want a properly damped response, with little ringing and minimal overshoot.

Morgan Jones has some simple to use equations on setting LC filter properties for low Fs and target damping of 0.5 to 1.5 as a an approximation. I have found these equations to be very helpful to get a well damped, non-ringing supply.
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Old 11th August 2008, 12:50 AM   #4
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Victor: I will try the 6L6 trick with a cheap chinese KT88, and I found the 6CA7 on the roll chart, but no 6QB5

zigzag: Got it. The inputs are in the current for load input box, worked great, thanks!
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Old 11th August 2008, 02:11 AM   #5
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Quote:
Originally posted by boywonder
Victor: I will try the 6L6 trick with a cheap chinese KT88, and I found the 6CA7 on the roll chart, but no 6QB5
I assume that's a typo. It's 6BQ5.
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Old 11th August 2008, 04:39 AM   #6
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Actually, I'm an idiot, the roll chart has a 6BQ5......thanks! (you'd think I would know a EL84/6BQ5 by now since my recently completed 1st amp is a baby huey)
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Old 26th August 2008, 12:38 AM   #7
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Default Another PSUD II question

When inputting the secondary resistance of the transformer in PSUD II (for a CT secondary), do you use the CT to HT resistance (1/2 the winding) or the resistance across the entire secondary?
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