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Old 4th March 2013, 08:08 AM   #11
Marra is online now Marra  United Kingdom
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Don't just turn one pot you need to adjust them alternately by half a turn whilst monitoring the output and the voltage across R11 or R12.They interact a lot turning one alters the voltage over both resistors.
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Old 4th March 2013, 12:49 PM   #12
rade95 is offline rade95  United States
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Thats not the problem, I can go as slow as 1/2 turn each on P1 then P2, makes no difference. Something is bad, either P ch JFET or N ch MOSFET, I think.
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Old 4th March 2013, 12:57 PM   #13
cviller is offline cviller  Denmark
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Marre could still be right - depending on where your trimpot is on its scale, there can be a lot of turns without any noticable effect. Best is to nul both and try again. Alternatively, you can take some good pictures and post them - someone might be able to spot something.
If you really want help, you can print out the schematics, place your ground probe on ground and measure voltage around the bias areas, write it on the schem, scan it and share it here on the forum. Then all the smart guys here will be able to help you quickly.
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