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Old 8th November 2008, 12:14 AM   #11
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are you saying R1 to source of Q2? because the diagram i saw on the passdiy zen amp shows gate of Q2 going to R1
both of the drains are connecting from both fets
i am using 140's not 240's juat so we are on the same page
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Old 8th November 2008, 12:18 AM   #12
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0 volts on the Gate of Q1 means no bias for Q1, and explains a lot.

What's happening with the resistors from Drain to Gate and Gate to
Ground? Is the input cap in place? Is the Zener backward or shorted?

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Old 8th November 2008, 12:28 AM   #13
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Quote:
Originally posted by fligti91
are you saying R1 to source of Q2? because the diagram i saw on the passdiy zen amp shows gate of Q2 going to R1
both of the drains are connecting from both fets
i am using 140's not 240's juat so we are on the same page

Yes, that's what I'm getting at. If you look at the schematic, you'll see that it's the source of Q2 that's connected to R1.

The pinout of IRFP140 and IRFP240 are the same.


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Old 8th November 2008, 12:29 AM   #14
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gate to ground is 0 ohms or a direct short. the zeners are pointed towards the power input side of the board. when probing between drain and gate of Q1 the resistance 20k plus and keeps climbing
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Old 8th November 2008, 12:32 AM   #15
Magura is offline Magura  Denmark
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By coincidence, I just helped a friend of mine sort the same problem out, and I made a pic, after I had written the correct connections.


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Old 8th November 2008, 12:34 AM   #16
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holy crap i think i flipped all the fets the wrong way. mr pass if you could take a close look at the pic i posted i flipped the gates and sources of all fets. was that a mistake? i thought i would need to because of the direction i mounted the mosfets
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Old 8th November 2008, 12:39 AM   #17
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wow thanks for the help guys. im going to flip these fets and see what happens.
what direction is the safest bet on the pots on first power up?
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Old 8th November 2008, 12:41 AM   #18
Magura is offline Magura  Denmark
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Quote:
Originally posted by fligti91
wow thanks for the help guys. im going to flip these fets and see what happens.
what direction is the safest bet on the pots on first power up?

Just set the pot in the center position, it really makes no difference.

If you have not already replaced the 0R22 with 0R33, do so before you power it up, as I suspect you're gonna run out of heatsinking pretty quick if you don't.


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Old 8th November 2008, 12:44 AM   #19
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here is my heat sink, how do you think ill be with this?
Click the image to open in full size.
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Old 8th November 2008, 12:44 AM   #20
Magura is offline Magura  Denmark
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Now to spare yourself a few blown parts, make sure you have the source of Q2 is connected to R1.

Note: The fets are not mounted the same way on both channels.


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