hi all im hoping to get some help in fixing our iie enhanced clone which displays wrong characters and has a background of apostrophes . It displays: Appde eee (on top) which should be Apple //e? also the ] is displayed as U? keyboard also seems to be delayed/hesitant?
the board beeps and boots fine and passes on board diagnostics? all psu voltage rails correct.
Ive done some research online and checked usual stuff like video rom/keyboard decoder 3600-pro etc and swapped out the cpu with known working but no change.
Was going to try swap out the IOU and MMU but the clone uses the STK ASIC chips i remember reading they are not pin compatible can anyone confirm?
So far this is what ive tried/tested:
ram - passed with onboard diagnostics (the display however is not the normal but rather checkered but it displays (in wrong characters) system ok
swapped out all system roms with known working roms - same screen
tried different keyboard, no change
logic board is clean, no traces are damaged
my thoughts are a faulty ttl logic chip? anyone know which one to check thats related to the video rom/decoder?
will update with photos of the screen im getting once i reconnect everything
thanks in advance:-)