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Old 11th September 2010, 06:02 PM   #4831
Salas is offline Salas  Greece
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Quote:
Originally Posted by SGregory View Post
The lytic decouple at the output did reduce what appeared to be higher order harmonics, but did not have the impact the the mkp did on Vin. I will re-install the lytic Vout decoupler and report back.
I was asking what happens if using the lytic instead of the 0.1u at Vin.
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Old 11th September 2010, 06:04 PM   #4832
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Here is something new. I did not remove the zobel just put 33uF across the output.

I repeated it with my other channel so it is a change.
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Old 11th September 2010, 06:08 PM   #4833
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Don't do that, its either a film Zobel or a normal ESR chemical cap. Things show the problem isn't the termination for now. It just went cuckoo with both.
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Old 11th September 2010, 06:08 PM   #4834
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I will try the lytic at Vin.
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Old 11th September 2010, 06:13 PM   #4835
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Tried the lytic on the input. Same as the mkp. Rest of circuit as designed except for gate stopper at 60R
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Old 11th September 2010, 06:19 PM   #4836
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Something is not right for sure. So the 0.1uF is good enough value across the input, I use it too sometimes. Look at my post about moving and changing the compensation scheme.

P.S. To get it right, you never saw a straight line on the scope, yes? It was a sonar ping there on all knob settings?
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Old 11th September 2010, 06:31 PM   #4837
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With it regulating, I never saw a straight line. I only see the sonar ping with the lytic on the output. Without the lytic on Vout it is a steady state oscillation. I should clarify the cap on Vin makes it SS oscillation closest to sine wave.

Darn. Just blew the semi's again. I accidentally unplugged Vin. Won't start-up now.
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Old 11th September 2010, 06:35 PM   #4838
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Its probably the error amp BJT or/and the 2SK. Is that a 65V device the BC you use there?
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Old 11th September 2010, 06:38 PM   #4839
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With it plugged in, I watched the output voltage slowly climb until it hit regulation voltage. The LED lit up and away it went working again. Will set voltage fine, but still has HF oscillation just like before.


The error amp is a BC546B rated for 65Vceo and 85Vcbo
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Last edited by SGregory; 11th September 2010 at 06:40 PM.
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Old 11th September 2010, 06:45 PM   #4840
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Its not normal, its struggling with some oscillation. If when touching with a probe the 9610's gate it will go on fast, its sure sign the oscillation upsets it. Try my post #4830. Its a thing that has a chance over revising the layout which will involve a lot of guess work. It does not change performance.
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