Sharp X68000 Pro #2

Acquired in August 2020 to try and get sufficient parts to repair the first, broken one.

The original auction listing in Japan described it as working, playing games and loading Human68k DOS, but that it took a while to power-on

“It will be a junk item. It usually works, but when the switch is turned on, it takes a few minutes for the power to turn on.
When the power is turned on, the image will look beautiful. The sound sounds beautiful.
I confirmed that the OS and game software can be started from drive 0.
Drive 1 is NG. The drive will eject after a few seconds after inserting the disc.
Input works correctly on the keyboard, mouse, and joystick.
Since it is an old used electric product, please give me a no claim and no return. ”

… “oh” says me after reading that; “that must mean it has a faulty power supply! Easy fix!”.

Yeah, well things don't seem to go very well for my Sharp X68000 adventures…..

There's a 1MB memory module which wasn't listed in the auction, so that's a small positive, but that barrel battery looks like it has leaked

The battery appears to have eaten a significant percentage of traces on the IO board

Battery removed and board cleaned as best as possible with thinners to remove all the crud, and vinegar to try to neutralise the battery leakage:

There's a couple of weird patch modifications to the board:

That large green capacitor isn't there on my other board, nor is that weird twin resistor on R70.

So it looks like the IO board (which is the main part I wanted) is a write-off. I can only hope that the floppy drive, main board and RAM module are working… and then try them in various combinations to see if I can improve the functionality of the original system at all.

About the only way forward from here is to use the intact IC's from the new IO board (the one with corrosion), transplanting them onto the old IO board (the one without corrosion).

Corroded IO board, with chips for removal:

Since I'm reasonably confident that the old IO board traces are intact, but that I've already had to replace several of the audio IC's, it's reasonable to assume that there are more faulty IC's.

To do this, I'll need the following DIP sockets:

• 1x DIP 8
• 13x DIP 14
• 5x DIP 16
• 1x DIP 18
• 4x DIP 20
• 2x DIP 24 double space
• 3x DIP 40 double space
• 2x DIP 42 double space, half pitch

Took images of the IC's I was removing, just to verify with the IC list I made for the original machine:

…. components removed from right hand of IO board:

Now to do the left hand of the board (the part which is heavily corroded)…

That's it. Completely depopulated of all IC's (except the two surface mount chips). Let's jump to installing those IC's on the original board.