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Old 1st January 2013, 10:22 PM   #31
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I doubled C9 (2 x 20pf each I believe - 20j caps). It didn't really change much as you can see.

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Old 1st January 2013, 10:30 PM   #32
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Default another thought

Both amps measure the same, so it is something about the construction, or I made the same component mistake on both boards.
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Old 1st January 2013, 10:58 PM   #33
Zen Mod is offline Zen Mod  Serbia
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chill for few days , then post more close-up pics
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Old 1st January 2013, 11:43 PM   #34
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Thanks Zen Mod,
I've taken 6 years to get to this point (on this amp)... Definitely not in a rush. Heading back to work tomorrow so I'll double check everything and update.
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Old 5th January 2013, 10:07 PM   #35
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Default Sweet sucess

After quite a bit of diagnosis, I finally found my wiring mistake that I made converting from the ZV9 to the F3. I am basically back to the original ZV9 (PD/Veteran boards). I still have the dip switches to play with turning off the ACS & feedback if I decide to.

Click the image to open in full size.

Once I got everything back together and adjusted (12.75dB gain), I got much better square wave results at 1kHz & 10kHz with 20pf cap. With a 5pf cap it still has some overshoot. I will fine tune this a little bit more...

Click the image to open in full size.
Click the image to open in full size.

When the amp was fully warmed up with the DC voltage at the output cap set to half of the Q3 drain voltage (41.4v/20.7v), I noticed that the sine wave clipped much sooner on one side).

I adjusted the output DC voltage until the output clipped at the top and bottom of the wave at the same time. This ended up being 23.85Vdc at the output with the drain voltage of Q3 at 41.4Vdc

The image below is 33v p-p with a 6.5 ohm load (41.4v supply voltage)

This is quite a bit away from 1/2 the supply voltage. Is this correct? or should I adjust it back to 20.7Vdc? Since I am trying to learn as I go, any additional feedback would be appreciated.

For reference, the voltage at the drain of the jfet is 3.56 & the source voltage is 1.13v with the 23.85Vdc at the output.

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I will continue to try to find a way to measure distortion to dial everything in...
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Old 5th January 2013, 10:23 PM   #36
Zen Mod is offline Zen Mod  Serbia
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everything is correct , now

you owe us ( me , us , whatever ) a six-pack , because of that wiring mistake

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Old 5th January 2013, 11:34 PM   #37
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Zen Mod,
A tremendous thanks for your help (and everyone else on this board)!

I am looking forward to hooking these up and enjoying them

I guess the next thing on the list is a B4 crossover to use my Aleph-x and ZV9's together............
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Old 6th January 2013, 08:19 AM   #38
generg is offline generg  Germany
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Fine you found this small conversion fault from ZV9 to F3 circuit. I remember I also made three faults when I used my F5 boards to make a BA-3 frontend....

Always easy in mind, but tricky on the board....
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