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In Reply to: RE: ok, what is happening here???? posted by cpotl on December 03, 2016 at 14:46:45
"If I understand correctly, your "square wave" is from a switching power supply operating at about 140KHz or so"
I'm pretty sure Vinnie has mis-stated the sweep time. All the lighting transformers I've purchased operate closer to 20 kHz out of the box. That's why the transformer must be modified. As for the waveshape, I did notice that on the later transformers. My earlier units were much more square. This issue definitely changes the method needed for ensuring that the tubes have the correct power applied.
Hate to say it, but I'm not sure I would use this method again. Pulling the square wave from a standard DC switcher and filtering it to a sine wave now seems to make more sense.
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Buy Chinese. Bury freedom.
Follow Ups:
I may have misstated the name, but the number was correct, it was 1. Like I said the symbol looks like a backwards y.
We are talking about the halogen AC transformer right, not the switching transformer?
I don't know what that could be. I've never seen a scope with any markings for time other than S, mS, uS and nS. I also can't think of any "1" setting for these categories that corresponds with 7 divisions, unless the frequency is *much* higher or lower than I've seen in these units. 7uS is roughly 140kHz. 7mS is 140Hz. Yes, we're discussing the lighting transformers with (supposedly) 12VAC output.
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Buy Chinese. Bury freedom.
I just went and check my scope. On the sec/div dial there are 3 sections, S, mS and the backwards y with a tip on the short end which probably equates to your uS, and the setting I was using was 1 uS in that case.
If you really have a 140 kHz lighting transformer, it would be very helpful to know the model number. A pic of the inside when you have time would also be of use. Thanks!
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Buy Chinese. Bury freedom.
I will take one in the morning and post it. It's bed time for this old fart.
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