M800 question

[paulbarrette]

I am reading about biasing and i assume i have to assemble the board and power it up. The j201 fets are from guitar pcb and are tested.
Measure the voltage and adjust the trimmers to 4.6v. I am not sure

Is there a link somewhere that shows how to measure the voltage? Or do people just adjust by ear?

Thanks
Pb

 

[KR Sound]

You’ll want to measure the left leg of the 5 transistors and get as close as you can to 4.5 ish

And you can absolutely do it by ear, but this will give you a good starting point.

 

[paulbarrette]

You’ll want to measure the left leg of the 5 transistors and get as close as you can to 4.5 ish

And you can absolutely do it by ear, but this will give you a good starting point.

View attachment 65635

Thanks! that pic helps a lot

Pb

 

[KR Sound]

Thanks! that pic helps a lot

Pb

You bet. You’ll find that it takes super tiny adjustments of the trimpots once you get in the right area.

 

[paulbarrette]

Awesome. That is good to know. I have a few weeks to wait for parts to arrive

Pb

 

[paulbarrette]

BTW is there an order you bias in? start at 1 and work your way to 5? 6 is fixed I think

thanks
Pb

 

[BuddytheReow]

Start at 1, go all the way through 6. Then do it over again. You'll notice the voltages have changed a little.

 

[paulbarrette]

Start at 1, go all the way through 6. Then do it over again. You'll notice the voltages have changed a little.

Ok, sounds good.

thanks
Pb