Analog vs Dig ground and RGB noise..

[leonk]

Just completed an RGB mod to my IFU-30 using the popular THS7374 RGB amp. on my PVM, it looks flawless but on xrgb mini slight jailbars. When I turn on LPF (GAME1 mode) they go away.

From experience, this is a ground issue. So I started probing around and trying to solve the issue. I noticed that expansion port has 2 types of ground - digital and analog. The audio jacks in IFU-30 get their ground from digital gnd!!  I tried moving gnd to amp and din port to analog gnd and the jail bars got much much worst.

The least jailbars are when rgb amp is next to expansion port with gnd from digital gnd and din out gets gnd from audio port port next to it.

thoughts? why 2 types of gnd and they are not connected!

oh. the pc engine of course had tim's jailbar cap fix done.

[Keith Courage]

I always run the Video ground wire to the Pin on the Din port and then the audio ground to the outer Din ground pole.

Some of these system still experience some jails bars even with the fix. The fix in lots of cases will just make the jail bars better as opposed to making them go away completely. Also, I've worked on a few PC engine systems where adding the jail bar caps made things worse. So it all depends on the system.

[gtsamour]

Does using the outer DIN shell ground as audio ground help with the buzzing experienced on RGB modded PCEngines?

[Keith Courage]

Nope, it's the cable. Generic cables cause the buzz. Get a good quality one from McKcris. https://www.pcengine-fx.com/forums/index.php?topic=18903.0