Ok I'm 95% sure I have this right, but want another pair of educated eyes to look at it before I make permanent mods to my CPU. Here's a clean version of the service tip:
http://www.videoengine.com/pins/jokerz/jokerzpix/level4/jokerzservicetip.pdf

Here's what my pcb looks like:

1.JPG 2.JPG

Mostly I want to make sure that they are asking me to slice away the trace. If so, what's the best way to do that, scrape it with an x-acto?

jeff_phx: Yes, all the screws in and tight. There's a known issue with jokerz!, where they didn't isolate the sound channel for some reason (missed in the board spin? I don't know), so this is a service bulletin to "reduce" the hum (doesn't totally eliminate), but believe me it's an annoying hum when it's not modded.

Does the board look like it matches the bulletin? I don't want to start cutting traces, but it sure looks like that's what they are saying to do

agreed.. probably going to shorten the leads too (just threw them on to post a photo). This may not even fix it (I hear if "helps"). Another forum said it went away completely when they took the ground off the spinner in the backbox for the cards, but then it couldn't spin (so it awarded bonus as default). Sounds like there's just a bad ground in the design.

well mod is done, didn't seem to help any. Found this thread about removing grounds until it goes away to find source, or replacing bridge rectifiers on the powerboard:
http://www.gamesforum.ca/showthread.php?p=2293734

cool, good to know. Well I'm starting with replacing all the caps first (since they do dry up, causing weird fluctuations in voltage). If that doesn't work I'm replacing the rectifier. Thanks for confirming.

caps replaced, didn't help. Listened REALLY carefully, found it was mostly coming from the left speaker, so I clipped it.. sure enough, hum went away (sound still comes out of other 2 speakers). can't believe all this trouble, and all I really needed to do was replace a bad speaker

$12 w/free shipping with prime:
http://www.amazon.com/gp/product/B0002BEPH6/ref=oh_details_o00_s00_i00

we'll see if the hum is still silent when I hook a speaker back up

I too have replaced every component on both sound board and powerboard (except bridge rectifier). My hum is only there when the left speaker is hooked up. If I remove it, it's quiet as can be (and it's not the speaker, I tried swapping that too). I'm down to either a bad cable for the left speaker, or there's just gremlins in the machine. If that's the case, I may just splice the sound from the lower speaker into the top speaker and call it a day. I know it won't be stereo, but it's better than a hum.

I believe I tried that (just left the speaker lying on the wood, removed all the ground wires), didn't help but I'll double check

Start disconnecting speakers to see which speaker is emitting it. I really did end up splicing the left speaker to the right. I also noticed the buzz went away when I disconnected the motorized cards in the backbox, so there's definitely some weird RF noise going through the audio.

My buzz was so bad, I don't know what was coming out of left speaker. Based on videos I've seen on youtube, I don't think I was missing any sounds. Even IPDB says it uses a "special version of stereo", which to me says not real stereo?

No, I didn't get that far, though I've read other threads where they've replaced it and it didn't help. It almost seems random where the issue starts. Supposedly many machines shipped with varying buzzing levels.

I can only see that happening if it's a brushed motor and the brushes are severely worn. Some resistors and diodes may help (don't know the values). I know when I was racing r/c cars, they started doing that to get rid of some of the noise because higher RPM motors would actually interfere with the radio