Sharp X68000 CZ-600CE - repair

[Higgy]

Hi,

After repairing my Amiga 4000 I started to tackle this project an early Sharp X68000 CZ-600CE.
First was to give it a clean as it had not been touched for years, this pic I had just clean the right tower:

Twin Towers

Tower.jpg (75.49 KiB) Viewed 4738 times

My friend mentioned PSU caps and a Google search showed that these are notorious in failing. Trying to remove the PSU, it has a nice hidden screw only accessible by removing the motherboard on the other tower (a YouTuber had to abort his strip down because of not finding this annoying screw!).

After removing loads of screws, as sure as Amiga batteries leak, the PSU was grim. But that was fine I did not fancy buying a Stepdown converter and was planning on using an ATX to supply juice:

Grotty PSU

Grot.jpg (47.54 KiB) Viewed 4738 times

Another search lead to the fact I needed to invert some Standby Voltage compared to ATX standard, so a little circuit board was built.
Many of the traces on the PCB are really fine, so battery acid can easily take out many. Which leads onto the motherboard and issue No.2. The amazing gut spilling battery.

Main board:

Main PCB

Mainboard.jpg (199.35 KiB) Viewed 4738 times

Lower board:

Lower PCB in base of case

Lower board.jpg (96.42 KiB) Viewed 4738 times

That's it for today.

[terriblefire]

Nice work. I soooo want an X68000 but it will never happen

[mrbombermillzy]

Nice work. I soooo want an X68000 but it will never happen

Yeah, a few years back, I was looking at importing one from Japan, but trashed ones that looked like they had literally been run over by a tracktor, were going for silly money. I guess I missed the boat on that one.

Keep us posted @Higgy

[HigashiJun]

Nice machines indeed, but cost prohibitive as @mrbombermillzy wrote...

[rubber_jonnie]

Such a cool machine, would be really nice to see some shots of it running when you're done.

I am resigned to the fact I'll probably never own one due to the cost, but nice to see other peoples

[Gooeyblob]

Nice work. I soooo want an X68000 but it will never happen

@terriblefire There is another project for you

[Higgy]

A bit of an update.
I replaced a couple of logic chips near to the battery which looked a bit eh (and were mentioned in other battery death posts to replace), and cleaned up a few solder joints.

board.jpg (80.73 KiB) Viewed 4542 times

Although my Main System crystal looked ok externally, most info on the Internet say the battery leakage kills it. So I took it off and underneath it looked grim:

Oscillator.jpg (14.52 KiB) Viewed 4542 times

Out of interest I opened the can. And sure enough the battery juice had gotten inside. Battery juice seems to have a thing for oscillators it seems!
The X68000 (or this one) has a frequency of 69.551199 Mhz, so yeah not going to find the same one elsewhere! Now you can get pre-programmed oscillators but I went the route of the Open Source project - Dual Frequency Oscillator:

DFO.jpg (44.66 KiB) Viewed 4542 times

(seems to be used for perfect PAL/NTSC timing when modifying consoles). https://nfggames.com/forum2/index.php?topic=5744.0 @exxos not sure if this would be a useful thing to make and sell? Programming can be done via a Raspberry Pi, no need for the programmer so quite easy for the end user to do (I did it ).

I made an inverter for the ATX Standby voltage following a Youtube video using some BC transistors and a few resistors.

So,I got me logic, I got me volts, lets hit the Power...

I live again.jpg (46.41 KiB) Viewed 4542 times

That is a good sign. Basically insert Boot Disk!

Ok I cut out the weeks of the thing not booting but I found the main +5V for the logic was low. Also I dug around in the spares box and found a 74LS04 chip to make the Standby voltage inverter circuit which is usually mentioned:
https://gamesx.com/wiki/doku.php?id=x68 ... eplacement
And now it powers on fine and 'Soft Shutdown' works.

That is all for now, next will be 'fun with floppies'

[rubber_jonnie]

Very nice, I love the look of these machines and find them fascinating.

[HigashiJun]

Very nice, I love the look of these machines and find them fascinating.

They were real home arcade machines.

Games on the X68000s are just great.

[rubber_jonnie]

Very nice, I love the look of these machines and find them fascinating.

They were real home arcade machines.

Games on the X68000s are just great.

All the vids I've seen on these machines really do show how amazing the hardware is.