Akai s900 weird problem

[autodefe]

Hi!!
I recently bought a cheap akai S900, of course not working!
The problem, is that when i turn it on all the characters in the display after showing the OS version, are arrows, pointing to the right.

The keys work, but in a really strange way, as if i would be navigating through the menus, but there are just numbers, no letters or something easy to understand........
After pressing several keys, the arrows change to the numbers in the LCD.

The floppy drive doesn't show any activity, i have the last OS in a floppy.

If i press the letter key, it jumps directly to the RAM test, no more keys pressed for this.

I have tried to remove the front panel and it remains the same, so no bad switches or similar.
I have tried reseatting connectors, ics, and nothing.
Of course no midi, and no sound output.
Any help or idea is welcome!!
Thanks in advance.

 

[Rob Flinn]

Maybe join the Facebook group "Vintage Synth Repair And Mods".  There are some really helpful guys there, whoc know all about this stuff.

 

[autodefe]

Hi Rob!
Thanks a lot for your answer and contributing.
Im one of those conspiracy believers.........and i don't trust fakebook and i don't like private groups. And of course, i don't have and never had a fakebook account, lol.
I would like to solve the problem on any of these forums, as it's easier for people who suffers the same problem to solve this issue. Also a lot of times I have found solutions for issues here, so this forums are a big help for everybody.

I have found an issue digging with the scope, i don't know if it's normal.
When tracing the RAMs outputs, i have found the CASKL and CASKU signals from IC88, are always HIGH, so the output for the RAMs is always LOW. As stated in the datasheet the CAS pin if it's HIGH, the output will be high impedance.
So the CASKL signal and the CASKU signal, control several ICs columns.

Could someone confirm this?