X68000 Pro - D.O.A from Yahoo Auction

Started by megatron-uk, June 17, 2020, 01:50:19 AM

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Powered the system on this morning to try and track down the keyboard issue.... and now I get a high pitched whine when its not in standby and no audio.

I just don't understand the problems with this system. Every cap was replaced after the faulty PSU wiring was rectified. It has two different sets of audio chips. Every IC on the sub-board has been replaced or at least swapped with the donor to verify that it behaves the same (other than the Disco chips behaviour is the same).... yet there are still issues with it.

The only option I've got left now is to try the main board from the donor with this fully recapped and chip-swapped sub-board. If that doesn't work I'm going to cut my losses with this; I just can't see what else I can do to get it working.


Couple of last checks:

- 5MHz clock is present on the SCC
- 4MHz clock is present on the YM2151

There is some 'strobing' going on with the 8255, so it looks as if the CS signal is being driven by the IOSC. Why the joypad doesn't work in this case, I don't know.

I'll try looking for the 4MHz clock to the keyboard port next.


Further info:

- 4MHz clock present on the 68901 (pin 35).

Also, has anyone been able to find the circuit diagram for the Pro?


Looking at the keyboard port itself, I see the following:


1 -
2 500mV logic high
3 ~400mV 'noise'
4 Some sort of signalling (see below)
5 500mV logic high
6 500mV logic high
7 500mV logic high



I've given up trying to get this working.

Two broken X68000 Pro machines and I've only managed to get things cobbled together in 8 months or so where it can actually boot - still no input, audio has gone strange again and the amount spent on spares, tools and the like is ridiculous. I'll put the two cases and the parts on Ebay and see if I can get anything back.

In the meantime I've bought a refurbished X68000 Super with working floppy drives, cleaned case, recapped motherboard and power supply.

It wasn't cheap (probably about the same as these two Pro machines combined), but I just need to draw a line under getting these working and move on.


Yeah, the moral of the story is that when it comes to retro Japanese computers there is no easy and cheap shortcut to ownership of a playable machine. I reached the same conclusion a while back. These machines are incredibly complex and fragile. The price of a professionally refurbished fully working unit might seem exorbitant, but it is well worth it.


damn, sorry to hear that you give up, the thread is really interesting (as your blog, with coding). I was about to take the same route and buy a 'junk' system. but now, i'm really hesitating...


I think the unfortunate thing is that if it weren't for the PSU wiring it would have been an easy restoration and fix. Not that I'm blaming anyone for that information - it's just one of those things.

I wouldn't be worried about replacing a PSU though - they're easily enough swapped out with a Pico PSU.


I recommend against buying a junk system in hope of scoring an easy recap fixable X68000. I have owned 5 x68000's, one compact XVI, one OG, and three ACE models.

They all arrived broken and my repair success ratio was 3 out of 5. One of the ACE's and the OG were plagued with cryptic hardware faults leading me onto an arduous and long repair "adventure" not unlike what has been chronicled here.

Lots of money and time was wasted in the pursuit of reviving them, even after recruiting the help of my pappy, a seasoned electro technician, I finally had to give up and cut my losses.

I sold the ACE, recouping a portion of my losses, and one of the revised ACE's, my best system, which ironically enough was destroyed courtesy of the british postal system.

In summary, the odds of getting an easily fixable system is not large enough for me to recommend rolling the dice on a junk system. Besides, even the junk auctions fetch a king's ransom these days, so I say just shell out the extra Benjamins and save yourself the headaches.


I think you're right, it's a huge gamble considering the taxes and shipping involved :<


Just read through all of this. I recently joined these forums right after I got my very first sharp x68000 from YAJ. Just like the OP i too decided to take a chance on one of the "turns on but operation cannot be confirmed" units. I haven't gotten the time to get into it yet but reading this thread I am both excited and terrified. So sorry to hear of your horror story. Hope I get lucky.


Well my Super has reached the UK, so hopefully it should only be a day or two until it gets delivered.

Although this one has been refurbed I still plan on disassembly to satisfy my own curiosity that any previous damage, if it was present, has been taken care of.

I also want to fit a Pico PSU, as running with a 110v Stepdown converter is not something I want to do long term... But in the short term I'll use my PC98 Stepdown to check that it works as expected.

Fingers crossed.

Edit: Well I've just had the duty/tax notice from Fedex... they want their cut now (of course)... another >£100 for it to be released to me....


The new machine arrived today, and it's super clean:

img_1916.jpg img_1917.jpg

img_1918.jpg img_1919.jpg

I haven't fully disassembled it, but enough to verify that it has been recapped (most, if not all)... perhaps not to my standards (the caps look to have been fitted on top of the board, rather than fitting them through-hole), and it has a new coin-cell battery with no visible leakage from the previous one.

The case is very clean (well, apart from down in the middle of the carry handle area), and is virtually blemish free - the marks on the photos above are mostly from my hands.

I did also pick up a SASI/SCSI to 50pin SCSI cable and mounting sled from ClassicPC Club at the same time, but I've just realised that I'm going to have to make something to go from the 3-pin Sharp HDD cable to the standard 4-pin FDD cable that the SCSI2SD board uses.

Next up is to test it and make damn sure it is working correctly.

Then, probably most importantly... is to find somewhere for it to go... I think I've goofed up and the shelf under which it was going to go is... erm... not high enough!


Well, it's good news - the new Super seems to be working perfectly.

It powers on and off okay. It will play the self-booter Motos fine, and it also boots a Master Disk v3 fine. Either floppy drive seems to work without issue.

I've got my Aranet keyboard adapter plugged in, and a Sanwa SKB-109LN Japanese PS/2 keyboard plugged in (same that I use on my PC-9821 and MSX2+) and it works as expected. I need to dig out a MSX joystick to try that, as well as a Megadrive controller (it came with a 'free' X68000 to MD 2-button adapter).

I've yet to install my SCSI2SD card, but while I'm doing that I really have to take a look at the PSU fan - it's very loud and also makes a squealling noise. I'll try and replace it with a quieter Noctua fan.


Well my MSX joystick doesn't work, but the MD adaptor and one of my old MD pads is just fine.

Wrote the Gradius II images to floppies and it all works - music out of the internal speaker is clear, loud and noise free (though tinny as you expect) and the headphone/stereo out is clear and thumping through my desktop speakers.

I'm still optimising the OSSC settings for the X68000 - I've got the sample settings about right now for a centred image that isn't cropped on either edge and scaled for my 1200 line screen, but I'm not quite there yet with the scanline settings.


But, I'm happy.


2 steps forward and 1 step back today.

Replaced the noisy PSU fan with a brand new Noctua, and it's much quieter... however, it has identified that the source of the squeal is the PSU itself, not the fan.

So, now I have to make the decision of whether to replace the PSU with a PicoPSU, or to figure out what else needs replacing on the PSU to cure this noise.


Power supply has indeed had all the (electrolytic) caps replaced, so the seller wasn't misleading me... and it does work, but clearly there's something amiss for it to squeal like this.

Any ideas which components would usually lead to high pitched noises?



I'd focus on the coils



Quote from: kroustibat on March 25, 2021, 06:05:30 AMHello,

I'd focus on the coils


Anyone know the specs? Most of the caps and resistors are listed in the wiki - I think there's just the one coil; L21, from what I can see.


I had a similar problem. Turned out the two big filter caps that I had replaced with ones of same spec as the failed ones were to blame. Once I replaced them with ones of higher capacitance the whining stopped.


Quote from: kamiboy on March 25, 2021, 07:33:45 PMI had a similar problem. Turned out the two big filter caps that I had replaced with ones of same spec as the failed ones were to blame. Once I replaced them with ones of higher capacitance the whining stopped.

I've got a pair of 6800uF caps on the way, based on your results. I'll try that and then if it doesn't work, look at the rest of the original components (all of the resistors I've measured are matching expected values).



My Super is now silent.... or should I say I have a Super-Silent? :D

Replaced the 5600uF caps at C41/C42 with 6800uF parts instead:




So, is it any better?... well, make your own mind up:

To my ears, it's absolutely silent!


Next steps, installing MIDI and RAM expansions:


Adding SCSI2SD, cable and mounting kit:


Initialising and partitioning SD card:


I've added a 1000MB partition and a 6552MB partition and installed GOVERHD. It boots fine from the 1000MB volume, and I do appear to be able to access the second partition, but haven't tried putting anything on it yet.

Next step is to get SUSIE installed so that I can access my SCSI Zip drive and start to be able to shuffle content over from my PC. I didn't want to simply write one of the disk images to the card, as that's not the setup I'm going for (plus, it's a pain in the bum when it comes to adding/removing/copying anything off).


Next task; getting a SCSI Zip 250 drive working, so that I can take data back and forth to my modern computers (one of which has a Zip 100, and another a USB Zip 250).


Seems simple enough. Set the Zip drive to SCSI ID 6, then:

Shows up, is browseable and I can copy data off it (which is lucky, since I don't have anything else currently available to test this SCSI Zip drive with!):


I'm testing it with something relatively meaty: the entire Multimedia directory of the V4 disk  image. It took a while to copy (forgot how slow these things are compared to your average low end SD card or USB flash drive!)... but it's all there. Now unpacking it (I seem to recall it being ~300MB) to the 6.5GB second partition), which may take a while!


Well, it worked. The ~150MB zip file uncompressed fine on the ~6GB second partition, and (several hours later) I had a full copy of the Multimedia/MDX folder structure.

In hindsight using an archive of approximately 14000 files was probably not the best, first test of the transfer.


So Susie and Human68k seem to be very fussy when it comes to the format of my Zip disks.

If I leave them in the pre-formatted state as supplied (I had a new, sealed box of 250MB disks I opened just for this) then they work really well (FAT16 and 8.3 filename limited, of course). If I reformat any disks (100 or 250MB) to FAT16 in Linux, then they won't read in Human68k (dir returns '0 files' and it locks up). If I (try to) reformat them in Human68k then they no longer read in Linux.

I need to do a bit more digging to find out exactly how the Iomega factory format differs - both are partition 4, FAT16, so it must be something else.


I did something similar only with MO disks, mainly because I was fascinated by the technology and had the excuse to invest in it. If you think zip drives are slow you should try MO. Snails pace does not cover it.

It is pretty neat though. Vastly inferior and more expensive to get into than, say, a simple external CF, or even zip. But to me with infinite more exotic ancient computer technology sex appeal.


For me, the appeal of the Zip drive is that it's vastly easier to ship stuff to and from the X68000 using standard FAT formatted media. I guess another AztecMonster or SCSI2SD would work for CF/SD media, but then I'd need an enclosure, wouldn't get removable media support (I'd have to reset between swapping cards etc). For as long as I've got some reliable Zip disks, this works really well... plus if I want to transfer just a couple of .X files I don't have to fire up yet another PC in order to use a 5.25" drive.

So far I've got the multimedia structure copied over, games and games2 from the V4 image.

I'm going through the mini_V2 image now and pulling out the games that are unique from that one. Hopefully I'll be able to drop those ones that don't use subst/hd2sim to the second partition. Of course, I'll add my game launcher metadata to those directories before I copy them over, just like the entire contents of the V4 image.


One issue I ran into was files with long filenames. I can't remember if I ever found a fix for it or not, but there are a few in the games folders if I remember correctly.


Yep, there are some games folders that definitely do not fit in the standard 8+3 FAT naming scheme. My Linux filesystem can handle almost all of the directories if drag-and-dropped from Disk Explorer, but there are some S-JIS filenames that get corrupted. For those, it's easier to use lha and archive them up inside Human68K itself (using the zero-compression option of lha for speed), and copy the .lha archive across in its entirety.

I know there is a FAT32/long-filename driver available, but it comes with it's own version of dir, cp, del, etc... so it's not a direct drop-in replacement.


Got the same problem while i used CDRW to transfer data to my X68000.


Quote from: megatron-uk on March 29, 2021, 11:04:22 PMI've added a 1000MB partition and a 6552MB partition and installed GOVERHD. It boots fine from the 1000MB volume, and I do appear to be able to access the second partition, but haven't tried putting anything on it yet.

I'm pretty sure the partition limit is 2GB with GROVERHD. You may find that you start getting file corruption if you store more than that on the 6GB partition.

It is for this reason I limited myself to 3GB. 1GB (1000mb) - 1st partition, 2GB (2000mb) - second partition. I've had no problems.

Your system is coming along nicely :-)