Quoted from minnesota13:The ground for the displays comes from and through pin 6 of J1 of the sound board. The circuit ground originates from J3-20 on the solenoid driver board. Both the sound board and displays share the same ground circuit. A weak connection at the solenoid driver board could be the problem.
Try running a jumper from a ground test point on one of the xpin displays directly to the solenoid driver board ground test point and see if that eliminates the buzz.
This is what i was hinting at on your Facebook post. Remember these displays suck up a bunch of 5v line current. This is creating noise that is some how leaking backing onto your sound board amp circuit. Isolating the sound board off of the backbox mount plate is kind of cheating a poor ground situation. It works some times.
Back of the driver board. Tie c26 negative lead and C23 negative lead to master ground. See pinwiki, it is documented there.
Make sure the cabinet and head ground braid is connector at the bottom middle of the head.
Make sure your rectifier board ground return pins are solid
make sure the driver board ground return pins are solid.
The sound board has two grounds. Logic level ground and a seperate ground return for the amplifiers. You get hum when these grounds are at different potentials. Can try to tie them together briefly via sound board test points and see if hum goes away.
Pull the rectifier board 230v fuse. It serves no purpose with led displays.
Coffs Harbour, NS
San Diego, CA
