WHY are you using a Y adaptor?
The A500 has stereo outs, and the 1084 monitor has stereo ins... are you insane?
Once you've tried a bunch of cables and perhaps an alternate speaker set (home stereo?) and you're still getting no sound from the A500- it could be a number of things...
rooted sound chip... or busted power supply. You can have a broken power supply that will still make tha machine go, but certian things like sound and serial ports won't work.
What the hell are u doing with an A500 anyway in 2004?

RW