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Old 21st May 2006, 12:41 AM   #11
poobah is offline poobah  United States
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Don't destroy the FET if you can manage it... just off the cuff guess.

The giveaway is that it works (well sorta) with power off...
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Old 21st May 2006, 12:46 AM   #12
jleaman is offline jleaman  Belgium
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Originally posted by poobah
Don't destroy the FET if you can manage it... just off the cuff guess.

The giveaway is that it works (well sorta) with power off...

Really ? You don't think it could be because there is still power left in the psu ?
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Old 21st May 2006, 02:23 AM   #13
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Default Re: BOSOZ L/R imbalance problem

Originally posted by dw8083

Any ideas what I should check for?

Another suspect could be the 100K resistors connected from the input and output points to the ground. I would check whether all four (per chanhhel) are of the same value.

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Old 21st May 2006, 04:56 AM   #14
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- Try to make the 124R resistance variable. So you can adjust the gain and match both channels (Min R value=max gain)
- Check the transconductance of your mosfets : Measure the Vgs of each mosfet @ two different currents using current sources (10 & 20 mA for example) Transconductance is given by Delta(I)/Delta(Vgs).The gain of the BLS depends on the 124R, the Drain resistors and the transconductance...

/Cheff - Falling feels like flying, until you hit the ground
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Old 21st May 2006, 04:08 PM   #15
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The values of all the resisters were checked and they are correct. I also changed the Fets, and the imbalance still remains.

I just got a topend B&K DMM that has a capacitance function. All the 10uf caps measure to about 10.5uf.... except one on the left channel -(neg) phase, I get no reading at all.

I'm going to order a new 10uf cap, and I bet I'll be in good shape.

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Old 21st May 2006, 04:18 PM   #16
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Select the 750 Ohm resistors (they estabilish the point of work).
Another way is to control the cap on the output, are you sure that they work well ?
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