Last weekend I picked up the VR boxes from Cyclo who was suffering badly from not-enough-space-itis.
Details
I didn't get much chance to play until late in the week so decided to start work on the Amigas as I know these reasonably well. Each chassis has an A3000/030 at the bottom with fly-leads coming from each port. These connect into a custom PCB mounted in the top of the case. Each chassis has a pair of TI-DSP based boards stuffed with ZIP VRAM to render the 'advanced' graphics. Finally, mounted underneath the lid is another custom PCB which handles the XYZ calculations from the hall effect sensors.
This board has connectors for the headsets which are based on an early EPSON (DSTN?) LCD which is logically split in two and viewed through some incredibly complex optics. Also linked into the top board is a joystick which uses hall effect sensors to provide XYZ placement. There are two resin dipped blocks which need to be hung from the ceiling and are fed from the chassis to provide the XYZ signals.
We knew from early exploration that the NiCads had leaked, oozing alkaline electrolyte over the board. It was localised to the rear left quandant, but was pretty nasty. We neutralised this with an acid and made lots of NaCl
Power-up
The chassis has a flicker fixer installed which in theory will present a 31.5K signal on the DSUB15. I powered up, heard disk spinup but saw nothing on the VGA screen.
I then scoped out the DSUB23 looking for a 15K signal and saw a working clock! I made a lead to wire this into my vintage 1084S and applied power. I got the black, grey then white screen changes much known to Amiga owners! Unfortunately the boot didn't proceed past this point even if left for some time.
I wasn't sure if this was due to poor SCSI termination (I removed the CDROM which was terminating the bus), lack of a keyboard (I don't have one) or because the boot config held using the RTC battery was gone (I'd removed the battery).
After stripping the machine to the bare essentials I still had no boot so started scoping the custom chip bus. This showed a worrying lack of signals other than a few Vcc and GND. I wasn't able to get to the CPU bus yet. After an hour of fibre glass pencil I removed most of the salt and oxide layer but still didn't see much hopeful. So I then totally stripped the chassis and got it under a magnifying glass.
Dead Hardware
Closer examination showed the following (pics to be uploaded later):
Dead:
74HC04N @ U477
74ALS74AN @ U480
48-pin socket @ U400 (Paula)
48-pin socket @ U450 (Denise)
18-pin socket @ U190
Dodgy:
Paula and Denise custom ICs. The legs show corrosion almost to the chip body, so I don't know whether there has been ingress.
68pin PLCC socket @ U478 (Amber)
86pin PLCC socket @ U205 (Fat Agnus)
Whilst this was going on I posted some wanted ads on Amiga boards, begged foreign ebay sellers to post to me and scrounged around for any salvageable bits.
Fix Plan
I've now split my plans into three threads.
1. Restoration of existing motherboard. I lifted the dead DIP sockets, pulled the corroded chips and will shortly be fitting new sockets and ICs.
2. Sourcing a new A3000/030 chassis. I've found a working but bare A3000D in Europe for 50 euros which is on its way. I'm hoping to use the customs and RAM from my 'dead' board on the new mobo. This is currently my best option as it has the same CPU and chipset as the existing machines.
3. Sourcing a fully working (and loaded) A4000. I managed to find a 68030 @ 30 MHz which is identical to the extand A3000, but it's running OS 3/Workbench 3 which is a later version to the OS 2.04 / WB 2.04 in the current system. I'm hoping the app devs used a decent compiler that followed the hardware guidelines after experiencing problems moving from OS 1.3 to OS 2.04 and finding very little worked. If not it looks like I'm porting the game exe to AGA graphics chipset

It's been a while since I had to ReSource a huge program, and it's not #1 on my list of fun things.
Software
Packaged with the hardware were a handful CDRs. Looking through these show that 4 are for the later PC versions but 2 are unreadable. The labels suggest these last two contain the Amiga version. I'm pretty sure the early Amiga CD-ROM didn't use ISO9660, so I'm hoping that the disks have a custom format rather than having unreadable bitrot.
I'm going to try a raw disk reader under Linux to make images which I can then mount in WinUAE. If I get no luck I've got an A570 CD-ROM drive which I can plug into my old A500 (Assuming it's not got clock battery leak too) to rip the software. Worst case I'll dump an ISO on the A500/A570 and then transfer it to a PC via a 115k serial link
. I believe the CDRs should be mixed mode with a few CDDA audio tracks (BGM) and a data partition for the software.
Risks and Mitigation
So, my current risks (and mitigation) are:
1. The SCSI hard disks might be dead. If both are screwed then I have no software, no means of finding any and am dead in the water.
2. I end up using A4000s and find the software fails because of hardware incompatibilities, most likely due to the AGA chipset. I can try to disassemble the code, get it back to 68030 machine language and patch it to work with the AGA chipset. My chance of success depends on how well the software was coded - using the API libraries gives me a much better chance of fixing by coding a library hook (kind of a DLL hook). Some of these fixes are trivial - not using the upper byte of pointers to store data, modifying illegal custom chip addresses. Others aren't so trivial - new blitter calling methods, relying on old hardware bugs etc. I really don't want to have to relocate the whole code to make room for my hacks.
3. Dead visettes (the headset unit). My chance of getting replacement compatible LCDs is about the same as acquiring the software!
So that's where I'm at currently. I'm hoping to have fitted new sockets and made an attempt at booting the board. I'll edit this and upload pictures too.
cheers,
tim