There are two, possibly three, mistakes in the experimental setup of #2,660
A. The sweep speed is far too slow; I expect to see something between 2 microseconds per division and 20 microseconds per division. Not 1000 usec/div
B. The scope is triggered on the rising edge; I expect to see it triggered on the falling edge. See "Triggering the Oscilloscope" on page 12 of the Quasimodo design note.
C. (??) I can't tell whether the blue horizontal line is, or isn't, the trigger voltage level. It's very close to the correct trigger level.
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A. The sweep speed is far too slow; I expect to see something between 2 microseconds per division and 20 microseconds per division. Not 1000 usec/div
B. The scope is triggered on the rising edge; I expect to see it triggered on the falling edge. See "Triggering the Oscilloscope" on page 12 of the Quasimodo design note.
C. (??) I can't tell whether the blue horizontal line is, or isn't, the trigger voltage level. It's very close to the correct trigger level.
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Attachments
Okay, was my error, sorry.
Now, the first measurement of a 20 VA donut - in this position I get 7,1 ohms for Rs.
Is the graph okay?
Now, the first measurement of a 20 VA donut - in this position I get 7,1 ohms for Rs.
Is the graph okay?
Many thanks Mark for the quick reply, I noticed my errors at the same time you wrote me.
Please twist the trimmer just a little bit to make the second bump (the downwards bump) maybe 1/2 of a vertical division tall, post a photo, and report the trimmer resistance which gave that photo. It may be that your resistance is perhaps a bit too low. After the photo requested here, we will know the answer.
In pictures: dial the trimmer until the second bump (yellow arrow) on your scope trace, strongly resembles the green line in Figure 10. Take a photo then report the trimmer resistance.
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In pictures: dial the trimmer until the second bump (yellow arrow) on your scope trace, strongly resembles the green line in Figure 10. Take a photo then report the trimmer resistance.
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Attachments
Thanks again, Mark!
Now, using the correct setting I get the following graphs.
1: without snubber pot
2: with 8,5 ohms Rs
It's my first real measurement, so the inevitable question: does it look right?
Many thanks in advance.
Now, using the correct setting I get the following graphs.
1: without snubber pot
2: with 8,5 ohms Rs
It's my first real measurement, so the inevitable question: does it look right?
Many thanks in advance.
Hi folks,
Today I received two AN-0218 transformers that I intend to use with the Zen Mod Balanced Preamp. I ran the Quasimodo jig on them and got surprisingly different results. The picture on the left looks like what I expected. Rs measures approximately 32 ohms on both secondaries. But the second transformer pictured on the right has a curve that looks different on the scope. Rs is approximately 128 ohms.
Any idea why they are so different?
Thanks,
John
Today I received two AN-0218 transformers that I intend to use with the Zen Mod Balanced Preamp. I ran the Quasimodo jig on them and got surprisingly different results. The picture on the left looks like what I expected. Rs measures approximately 32 ohms on both secondaries. But the second transformer pictured on the right has a curve that looks different on the scope. Rs is approximately 128 ohms.
Any idea why they are so different?
Thanks,
John
Attachments
I don't expect the 20VA Antek's to be dramatically different than the 10VA Antek's measured in the Quasimodo results (ONLY) thread, post #163.
Double check that you haven't accidentally swapped Cx and Cs
Double check that all transformer primary wires are firmly shorted together. See QM design note Figure 13.
Double check that all secondary-not-under-test wires are shorted together
Double check that you get the same result when you swap the two secondary wires going into the green Euroblox connector marked TRANSFORMER
Double check that you're triggering on the falling edge; the pictures appear to show that you're NOT.
Double check that you're setting the triggering level appropriately: about -5.0 volts when using a 9V battery. (hint: look at top right. It's not good)
Remove the transformer wires and replace with a fixed inductor. Remove trimmer. Double check that you get a waveform with LOTS of ringing that decays pretty darn slowly
Double check that you haven't accidentally swapped Cx and Cs
Double check that all transformer primary wires are firmly shorted together. See QM design note Figure 13.
Double check that all secondary-not-under-test wires are shorted together
Double check that you get the same result when you swap the two secondary wires going into the green Euroblox connector marked TRANSFORMER
Double check that you're triggering on the falling edge; the pictures appear to show that you're NOT.
Double check that you're setting the triggering level appropriately: about -5.0 volts when using a 9V battery. (hint: look at top right. It's not good)
Remove the transformer wires and replace with a fixed inductor. Remove trimmer. Double check that you get a waveform with LOTS of ringing that decays pretty darn slowly
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