STF/M 512K to 1MB - C070789
Posted: Sat Sep 30, 2017 12:26 pm
Here the STFM has only 512K of RAM fitted (Bank of IC's on the left). The bank on the right has space for another 512K ram.
Also note that 3 resistors are missing in this case. R71,R72,R73.
First up - Unsoldering all those holes for the RAM and capacitors!
Now I unsolder the 6 resistor holes and clean up the PCB with DE-FLUX cleaner.
I fitted all the RAM into sockets as the new RAM was taken from old STFM's breaking for spares so the state of the ram was unknown. Capacitors (220nF) were also taken from old boards.
The 3 resistors (68ohm) Were again taken from old boards.
The bottom of the PCB shown after cleaning up the solder flux!
We now have 1024K ready to play those 1MB games with
Ram tested fine even after 500 passes. So all the RAM fitted has been tested OK
RAM TEST SOFTWARE