Posted by Ben Weaver on August 30, 2006 at 08:59:19:
In Reply to: Repairing a QS8: CALLING ALESIS TECHS! posted by Reid on August 27, 2006 at 23:53:43:
It sounds as though you're on the right track. It could also be the address driver for the roms that has got stuck - if the appropriate three address lines aren't being driven properly (maybe open?) then the address decoder could be stuck driving just the first rom.
The thing I'd do is get hold of the pin-out for the roms and scope the chip select line on all the roms. If they seem to be behaving, then it's maybe an address bus issue. If that seems to be playing ball, then it might be a data bus issue. If that seems okay, it might be seven fried roms. But as you say - that sounds unlikely.
Best of luck!
Ben
~~~
: But... I'm an electronic hack - I mean tech - of some ability, and I can't resist trying to fix it. I got hold of an old (same vintage as the board) Alesis service manual. I've run the onboard self-tests, and the sound ROM tests are failing for all the ROMs except #1. I haven't yet looked at the circuit board, but based on the schematic and the test results, my first guess is a broken bus trace after ROM 1. (Could 7 out of 8 ROMS really have failed?)