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Old 9th November 2003, 01:01 PM   #1
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Default zen and irfp240

Hi,
I'm newbie in audio and i'm working with Zen first variation. I use IRFP240 instead of IRFP140 (i can't find IRFP140 in my country). After a few seconds R1 (0R33/2W) is really hot and it smokes. I take 2R0/5W inestead of it. Now i have about 1.1V on R1. Is it OK? Or should i change R6/R7?

regards,
pawel.
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Old 9th November 2003, 11:47 PM   #2
B.L. is offline B.L.  Poland
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I can find IRFP140 for You
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Old 10th November 2003, 01:36 AM   #3
moe29 is offline moe29  United States
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Make sure that P1 (the potentiometer) is set at half or less when
you power up the amp. If it is at full that will cause what happened
to you - and probably toast your FETs too.
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Old 10th November 2003, 08:14 PM   #4
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Mhm, and it is good idea to use R1=2 Ohm instead of .33?
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Old 10th November 2003, 10:50 PM   #5
moe29 is offline moe29  United States
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A value of 0.33 ohm, 2 watts for R1 works - if the circuit has been
correctly assembled. Other parts will work, as Mr. Pass mentions
in the article, but i would say it's probably best to stick as close as
you can to the parts list for your first build. After you have a
working amp, feel free to experiment from that point - A good
place to start would be the upgrades reccomended in the
Zen Revisited article that can be found on the PassDiy web site.
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Old 11th November 2003, 02:24 AM   #6
MikeW is offline MikeW  United States
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Default Bias

The voltage drop should be .66 volts. It is set by the base to emitter drop of Q3. The value of R0 (.47 ohm) and R1(1 ohm) set the bias. They are .33 ohms together it is .66/.33 or 2 amp bias. If R0 (2 ohm) and R1(1 ohm) that would be .66 volts/.66 ohms or 1 amp bias.
IRFP 240 should work fine. Good luck.
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Old 11th November 2003, 02:30 AM   #7
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From my personal experience I would check the orientation of Q3. I'll be darned if I screwed that up twice. I burned R1 and lost fets until I realized that the circuit wasn't regulating the current properly.
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Old 11th November 2003, 09:15 AM   #8
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Quote:
The voltage drop should be .66 volts. It is set by the base to emitter drop of Q3. The value of R0 (.47 ohm) and R1(1 ohm) set the bias.
I don't have R0 yet because it isn't in the zenamp.pdf. So should i insert it somewhere?
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Old 11th November 2003, 04:57 PM   #9
MikeW is offline MikeW  United States
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Default V4?

http://www.passdiy.com/projects/zenv4-3.htm

This is V4?
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Old 11th November 2003, 05:02 PM   #10
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No, this is first zen project (www.passdiy.com/pdf/zenamp.pdf).
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