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Old 25th April 2003, 07:07 AM   #1
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Default Dumb Zen V4 Question

My long labored V4 was finished on the coffee table of a hotel Wed. night. But I had left my selection of fuses at home. I am planning on turning it on to check for smoke this weekend. If it works I will post some pictures.
I have a stupid question about adjusting the drain voltage on Q1. The instructions say to open R4 to maximum value to start. L ooking at the circuit it appears that to get the drain voltage low to begin the pot should be closed (set at 0 ohms). This would bring the gate voltage down close to zero. Is this correct, or do you really want the pot open (25K) when first throwing the switch?
I checked the reading on the pot, and I am getting 20K on one channel and 17K on the other with the pot all the way open. This is in circuit. This 15% difference seems high.
Thanks if you reply, I would hate to do anything to decrease the chances of this unit firing up okay the first time.
I work slow and do sloppy work. Must have 30 hours in this V4. Hope to get quicker and cleaner!

George
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Old 25th April 2003, 08:02 AM   #2
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When R4 is at 0 ohm, no current flows through Q1. We are recommended to begin the adjustment of the pot on this condition. Increase R4 slowly until you meet the drain voltage of about 22, and stop there. If everything is OK, the final value of R4 would be set around 10k.

Hope this will help.

JH
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Old 25th April 2003, 07:07 PM   #3
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Actually, it does not matter at all where you start.
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Old 26th April 2003, 03:06 PM   #4
miguel2 is offline miguel2  Portugal
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Doesn't this value affect the current through the transistors? I though that if you start the wrong way you would burn the whole thing...
I will not argue with NP, but if I were you (and I been there before ) I would turn anti clock wise and turn the power on then.


Miguel
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Old 26th April 2003, 05:15 PM   #5
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I think it affects the current in so far, it could shut the FET and about no current goes through. (because the current source recives limited voltag from the regulator, else mybe we would see a sparc) But main effect should be to set the voltage which appears at drain. The current should be determinated by the current source and the resistor setting into the CS.

Whe i fired up my ZEN V4 first time i remember i set the pots to 50%.
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