Aion Overdriver bias issue

[RRJackson]

I built Aion's Colorsound Overdriver PCB (the Plasma) and when I went to bias the transistors the trimmers for Q1 and Q2 won't get me to the voltage I need. I was shooting for 4.8 volts (as per the instructions) and the trimmer on Q1 only gets me as high as about 2.2 volts. Then Q2 will get me up to 3.6 volts and finally Q3 will go to (and past) 4.8 volts.

Anyone got any ideas why I'm running into this? I used BC109C transistors.

It actually sounds pretty cool. I'd never tried one before. It wasn't what I expected, but now the old Jeff Beck tone makes a lot more sense to me. I powder coated an enclosure I picked up off eBay and thought it turned out kind of cool...aesthetically, at least.

If I can figure out where I went wrong, I think I'll build another one of these boards and try to get it right this time.

-Rob

[slacker]

Q1 is only supposed to be biased to 2 or 3 volts, so there might be nothing wrong there. I would just set the Q1 trimmer in the middle which should be close enough for rock and roll and then you should be able to set Q2 to 4.8 volts. If you can't get Q2 to 4.8 volt then I would check all your resistor values round Q1 and Q2 are correct and that all your connections are good.

[RRJackson]

With Q1 at 2.1 volts, I was able to balance Q2 and Q3 at about 3.8 volts, which sort-of, kind-of seems to work.

Q1 is only supposed to be biased to 2 or 3 volts, so there might be nothing wrong there. I would just set the Q1 trimmer in the middle which should be close enough for rock and roll and then you should be able to set Q2 to 4.8 volts. If you can't get Q2 to 4.8 volt then I would check all your resistor values round Q1 and Q2 are correct and that all your connections are good.

[aion]

You might also try switching around the transistors and seeing if that changes anything. Q1's bias is set up differently than the others, though, so as slacker said you won't be able to get all the way up to 4.8V (and shouldn't). From what I understand, that trimmer has more to do with the AC signal than the DC.

Great looking enclosure!

[RRJackson]

You might also try switching around the transistors and seeing if that changes anything. Q1's bias is set up differently than the others, though, so as slacker said you won't be able to get all the way up to 4.8V (and shouldn't). From what I understand, that trimmer has more to do with the AC signal than the DC.

Great looking enclosure!

Thanks! I'll give it a shot.

I set up a little improvised powder-coating workshop in one of those Shed-in-a-Box tents out in the back yard. I put down a grounding stake to aid in grounding the enclosures and set up a little toaster oven to cure the powder. Seems to work pretty well.



-Rob