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Old 4th February 2013, 07:50 PM   #21
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Quote:
Originally Posted by ikoflexer View Post
Keep the gate resistor 1k and replace the cathode resistor that sets the current with a 2k variable resistor and very carefully adjust it in the circuit. If that doesn't make it work then switch to a gyrator (just an extra couple of resistors and one capacitor) which will probably work better anyway. (Be careful adjusting that resistor with the high voltage present.)
I'm not familiar at all with the gyrator circuit. Do you know a good resource that will help me?

I'm going to replace the left channel CCS first, as the right channel seems to work fine.

Thank you.
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Old 4th February 2013, 08:09 PM   #22
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How is grounding, local decoupling? Sounds very much like motorboating - the CCS raises the OLG compared to a resistor and voila.
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Old 4th February 2013, 08:12 PM   #23
ultrafi is offline ultrafi  United States
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Stop! Read the datasheet for the 10M45. You really need more current through the 10M45 for it to work well.
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Old 4th February 2013, 08:16 PM   #24
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I believe the grounding is OK.

OLG?

Quote:
Originally Posted by analog_sa View Post
How is grounding, local decoupling? Sounds very much like motorboating - the CCS raises the OLG compared to a resistor and voila.
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Old 4th February 2013, 08:20 PM   #25
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Originally Posted by ultrafi View Post
Stop! Read the datasheet for the 10M45. You really need more current through the 10M45 for it to work well.
My datasheet says good for 2 - 100mA. I used the data sheet to calculate the correct resistor. I could not find on my data sheet where it says it needs more current to work well. I am interested in reading more about that. Do you have a link?

Thanks.
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Old 4th February 2013, 08:20 PM   #26
iko is offline iko  Canada
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Quote:
Originally Posted by ultrafi View Post
Stop! Read the datasheet for the 10M45. You really need more current through the 10M45 for it to work well.
+1
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Old 6th February 2013, 08:58 PM   #27
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I disconnected the gNFB feedback loop today and voila, the CCS works fine.

I haven't had time to go any further. Since the right channel worked, and the left channel had the problem, I'm guessing that one of the output transformers had the blue & brown plate wires reversed from the factory.

I'll put it on the scope when I get a chance and verify that.

Thanks for all the help.

Scott
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Old 6th February 2013, 09:48 PM   #28
AJT is offline AJT  Philippines
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you still need to add a small resistor in series with the led and connect the gnfb resistor to that resistor.....
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Old 6th February 2013, 09:52 PM   #29
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Quote:
Originally Posted by ikoflexer View Post
Keep the gate resistor 1k
http://waltjung.org/PDFs/Sources_101_P2.pdf

Page 3
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Old 6th February 2013, 09:53 PM   #30
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Quote:
Originally Posted by Tony View Post
you still need to add a small resistor in series with the led and connect the gnfb resistor to that resistor.....
Yes Tony, that's how I built it originally. A 100R resistor in series with the LED and gnfb applied at that point.
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