Akai S1000 / S1100 samplers

Hello to all,

i'm new here, and i have a Problem with my S1000.
If i play the internal 4 Sound's with the Play Button, or via MIDI, only the Sinus and Sawtooth Sound works. The Square and Pulse are only produce an muffled Klick.
If i load Sounds, these are not working. Some are not to hear, others are distorted or undifferentiated Noises.
The Sampler has the 2.2 System. But i can load the 4.4 from Disk and it seem's to Work fine.
Equipped with an 8Mb Expansion, it displays only 5Mb. The Original 2Meg and Expansion 8Meg at half. I Think, there is an Damage at the Memory Controller, or an BUS-Driver Chip.?
Does Anybody know, what Damage this be, and how i can repair this?
I'm an Hobby Electronic Freak since 25 Years, and Specialist for Computer and Network, so i Think, i can repair this, if it no so great Problem. ;-) But i don't have an Service Manual, Schematic Diagram ore Special Tools an Measuring Instruments to find the Error.

Thanks.
Regards Mario