Here’s my little Game Gear prior to repair. As you can see from the above it has very quiet sound and no video, overall not bad condition on the inside of the unit. I hope to replace the capacitors inside the unit soon and retest – hopefully with more video. Stay tuned…
Good news, the co-processor has arrived and is recognised perfectly. I’ve been able to run MEMTEST 4.10 on the 16MB of RAM (That’s the maximum!) and it has passed with no issues. MEMTEST 4.20 doesn’t run though – it restarts when trying to boot off the floppy.
Now I am waiting on the battery for the RTC to arrive from Hong Kong – still a couple of weeks to go. I have also ordered a Disk on Module (DOM) that is 4GB in size and based on SLC. Hopefully it will be recognised OK in the BIOS and be able to boot DOS and Windows with no issues. Time will tell!
So the new motherboard went in and POST passed OK, hard drives were recognised perfectly. Sadly this indicates that the 386 board that was originally in the machine has an issue with the hard drive controller on the motherboard. It will still be a good backup board though.
I will see how bigger hard drive the machine will recognise and from there purchase a Disk On Module (DOM) which, as far as I can tell, is a flash drive that can hook into a PATA port. They are very low sized – which will be ideal for this system.
However, I did hit a show stopper with the real time clock battery being flat. This prevented the machine retaining settings upon reboot (Yes! Even if the power was connected! Dammit!) and there is no way to bypass it without hacking apart the chip.
The particular chip in question is the TH6887A with a date stamp 9309 as pictured above. Thankfully, these batteries do not leak all over the motherboard like the “Sealed” NiCad on the 386 board. Unfortunately they are a pain due to their non-standardness. Removing the chip causes the machine to beep on startup – it contains more than just a battery I discovered.
They can be substituted with a Dallas DS1287A or DS1287 – which one I am not sure. Chances are they both work, so I’ve ordered one of each from China. Lead time 2-3 weeks, bummer. The wait begins again.
While I was on eBay I picked up a coprocessor for the 486 board also. It was a ULSI US83S87 SX/SLC33 MATH COPROCESSOR 68-PIN PLCC. 33MHz to run inline with the 33MHz 486. Failing that I was going to pickup a Chips coprocessor rated at 35MHz. If you choose less it can give false results. I figured it is better to be safe than sorry. Not that coprocessors are utilised much for what I’ll be using it for.
I am also still waiting on my 4x4MB RAM chips to arrive from overseas. Very exciting times. The video RAM on this motherboard already appears to be maxed out and that is great news! Scorched Earth!
It does look like the onboard VGA can be disabled and an ISA video card be run, however I do not think it would fare too well with the Mega Drive card. Also above are the jumper settings to bypass the Mega Drive card and run in PC only mode. And finally a readout of the auto-detected hard drive settings – Thanks American Megatrends!
Picked this up on eBay from the UK and have given it a bit of a clean out. It has become my favourite Mega Drive controller now. The insides are equal to another Mega Drive controller I cleaned out yesterday also – sadly it had some tabs snapped off the D-Pad.
Should go well with the Mega PC, still need to track down an Amstrad mouse, keyboard and joystick though. Unfortunately the controller type Amstrad used is also the worst type of Sega controller design (in my eyes at least). The D-Pad isn’t very responsive at all. At least it is a great cream colour!
Here’s how to replicate the fault – Run the Saturn for an hour or more so it becomes nice and toasty. I found that the music player was more than sufficient to do this.
Next take the Saturn apart while it is still nice and warm and record alongside the power supply (in stereo) to help narrow down which component is at fault.
I suspect either one of the transistors / bridge rectifying diodes or the transformer. I am absolutely in no way an electronics pro though. I can tell you that using a power supply from my both my model 2 Saturns does not cause this to happen. Anyone know a good electronics repair shop nearby?
I’d buy the power supplies separately if I could track them down – but they seem to be getting a little rare due to the age of the unit most likely.