Taking a quick detour from oscilloscope repair to attempt to fix a RAM error on an Akai S900 sampler that I just scored for cheap. The two issues were a dim backlight, and RAM error “Bad RAM Bit DK09”
Thanks to DOSputin for compiling a reference of what codes refer to what chips here.
The best copy of the service manual can be found at this page, along with a wealth of other info on the S900.
DK09 refers to IC62. This thread confirms that there’s no way to test them all at once; you only get one bad ram message at a time, which means you have to take the whole damn thing apart, change the ram, reassemble it, then do the test again to find out where the next problem is.
Someone has been in this unit before. 3 of the 6 screws to attach the voice board were missing. It appears someone had dealt with a RAM issue before, as IC60 is now socketed. I’d planned on doing the same. After replacing IC62, I get another error: DJ12 – IC57. Fortunately, that was it, now the RAM test passes.
The latest firmware is V1.2C. I have V1.2A. I don’t think this matters, as I boot to what’s either called OS2 or OS4 with a floppy.
Thanks, excellent information, could you tell me where you got the chip and the socket?
Hi Paul! I’m in the same shoes as you were with bad RAM bits. Would you mind to share the place where.did you get the new chips from? Many thanks in advance for your reply!
Hi Richard – I got them on eBay, there appears to be a number of US sellers with reasonable prices. The number after the dash (mine are 41256-12) is the access time in 10s of nanoseconds. Going faster is OK, but I wouldn’t go slower (a larger number) just in case. Get some sockets as well, and leave a few extra RAM chips in an antistatic bag taped to the inside of the case so you’ve got ’em handy if more ever go bad.
Cheers
Paul