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Old 4th April 2008, 01:00 AM   #21
MikeW is offline MikeW  United States
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http://www.passdiy.com/pdf/zen-v4.pdf

Look at this one page 5.

The one for the F3 is a split rail. This is the one you want.
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Old 4th April 2008, 01:37 AM   #22
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Ah, that makes the series wiring more apparent. I think the F3 power board is accomplishing the same thing with the two jumper wires that can be seen on the center of the board in some of the photos. Correct?
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Old 4th April 2008, 02:28 AM   #23
MikeW is offline MikeW  United States
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I think he put the wrong power supply in that article. It may be for the F4.
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Old 4th April 2008, 02:48 AM   #24
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I'm pretty sure it's the correct power supply.

http://6moons.com/audioreviews/firstwatt4/f3_2.html

Look at the 5th picture down.
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Old 4th April 2008, 02:56 AM   #25
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Hello Marsfrogie, Check out www.firstwatt.com for manuals on the various firstwatt amps that Nelson Pass has done. Once he has completed production on a particular model, he is kind enough to post the full manual, including service information and schematics on this site. He also has other designs at www.passdiy.com

Peace,

Dave
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Old 4th April 2008, 02:59 AM   #26
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??? I've read that site upside down and sideways 3 times through. That's why I'm pretty sure it's the right power supply board. It doesn't help that I don't understand most of it though.
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Old 4th April 2008, 10:24 PM   #27
MikeW is offline MikeW  United States
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The power supply doesn't match the schematic for the amp. The 6 moons article thinks a MOSFET is a power JFET. I have built this amp. Use the power supply in the Zv4 or get the boards from Peter D.
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Old 4th April 2008, 11:52 PM   #28
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It's the same board, but it's strapped differently for +/-23V
or +46V or two isolated +23V.
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Old 4th April 2008, 11:59 PM   #29
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Thanks Nelson,

Look at the F3 service manual guys, PSU PCB, options A,B and C ( the one for F3 ).

Naturaly this means that the schematic changes....the GND line ( for F3 ) will be the ( - ) and both center taps are just connected together ...not connected to audio channels.

Right Nelson ?



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Old 13th April 2008, 09:03 PM   #30
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Well I finally got the amp mostly together and think I either have a short in the right channel or blew something.

Looking on the First Watt F3 R0 Schematic here are the voltages I get at the measurement points. The amp does not generate sound.

Input Target 46V Left: 42.9V Right: 42.9V
Next to Q5 Target Voltage 41V Left: 30.2V Right: 34.4V
In front of C1 Target 21V Left:16V Right:0V
Next to Q2 Target 3.5V Left: 0.6V Right:0V
Jfet voltage Target 1.1V Left: 0.6V Right: 0V

Any advice on where to go from here? I am out of ideas. On the left channel I was only able to get 16V tops by adjusting the potentiometer. Any help would be greatly appreciated.
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