NEC PC-9801VX – Floppy Drive Maintenance

29Nov/211

NEC PC-9801VX – Floppy Drive Maintenance

If you have the opportunity, do NOT use floppy disks... for anything... ever. I've just spent a lot of time debugging issues when I should've been playing A-Train! Due to the effort I've spent, I hope the answers you find in the rant below help you and prevent such effort expenditure. The goal was simple: The PC-9801VX was up and running and I wanted to run this...

Yes, it's another version of A-Train. It's version 2, still prior to the version 3 that was released internationally. Now that I think of it, I'd actually purchased this game with a bunch of trains back here! I'd done nothing with it since... but now finally had a machine to run it on.

Unfortunately, the drives wouldn't even accept floppies!

I can't insert a floppy disk!

When this unit arrived, I tried to insert A-Train Disk A into Drive A. The disk would slide 70% in and then hit something. I decided not to push my luck and opened everything up...

If you've noticed too much copper in the photo above, then you'd be spot-on. The 'head cover' of the read head has popped off (presumably in transit) and sat itself in front of the read head. This has succesfully blocked the floppy disk from inserting all the way. As these machines are super-popular in Japan, a quick Google found many examples of people having the same issue. I opened up the second drive and found the same issue!

Each site that mentioned this issue had a different solution! Leave the cover on, take it off... leave it on? take it off? I'll do the latter... for now.

Expired capacitors

Now that the floppies could enter the drives, I tried to boot the machine. Drive A would do nothing... it'd just pretend there was no floppy at all. Drive B got as far as below and then noisily failed. The failure let me believe that it'd at-least loaded a bit of data from the disk.

So, what to do? Fix Drive A first, then work out if it could do better than Drive B. I've already hinted to the issue, but it all became very obvious after extracting Drive A and flipping it over:

What a mess! A quick google around found this article on FD1155D maintenance and, to my surprise, it actually mentions how to fix this exact problem. It mentions that if the disk isn't found and the motor just spins (which it did), then these capcitors are to blame. After a quick bit of cleaning and soldering, the tracks actually proved to still be conductive. I added a jumper wire anyway and replaced the capacitors as required.

Shit job, I know, but.. it worked! Drive A now produced the SAME ERROR as Drive B! Progress!? Based on process-of-elimination, if both drives produce the same error, it's no longer the drives at fault. It's the motherboard (in-built controller) or the floppy disk!

Making my own floppies

First things first: make sure you have an old PC with a known-working 5 1/4" drive. Don't even bother going down this route if you have suspicions about the PC side of things. I went around in a few circles at the start as my floppy drive half-read the first disk I put in, only to totally reject everything after. The fix? Clean the heads with an ear-bud (q-tip?) and isopropyl alcohol! After that, it worked like a dream.

With the floppy drive functional, and Win98 Japanese version installed, I could then use the tools to get floppies written. I followed the instructions here and downloaded both Virtual Floppy Image Converter and Disk Copy Utility. Aim for the green download buttons on the pages when you're trying to obtain the software.

From here, everything was extracted and a relevant DOS bootdisk was found from the PC-98 Software Dump archive over at archive.org. There's also a bigger archive here, for those interested. The DOS disk image was inside the OS folder in FDI format, so it needed to be converted first. Go to the Virtual Floppy Image Converter folder and double-click the exe.

Choose English and then set the default output location.

Finally drop the FDI image onto the app and a DCU file will be spat out. With a blank/spare floppy disk in the 5 1/4" floppy drive, open a DOS prompt and browse to the folder where the DCU image file is. Alternatively you can browse to the DCU application folder and just edit the command line below to find the DCU image file.

c:\DCU\DCU.exe -f @C:\PC-98\A.DCU,0

Above, correct the path for DCU and the path and filename for your DCU floppy image. The -f means format the sector prior to writing and the ,0 means write to Drive 0. This is A:, with Drive 1 being B. This software also runs on the PC-98 where the drives are 1,2,3,4 and not A,B,etc...

I tested writing the DOS 3.3 disk to a blank floppy first. It ran quickly and worked flawlessly .. My PC-9801VX booted this newly-written disk to an installer! No hard-drives on this unit yet, but this made me pretty darn happy! I then decided to try and re-write the A-Train Disk A. It was already broken, so why not just try and re-write the same image back to it. The disk image is actually in the same archive above, so I extracted it, converted it and tried to write it...

I first tried to write the DCU file to a blank disk and this completed with no issues, so I put it to the side. I then tried repeatedly to write the image back to the actual A-Train floppy, after removing the copy-protect tape. It kicked off and threw me to an input prompt very quickly. This prompt, as shown above along the bottom line, gives you a few options when DCU hits an error: R for retry, F for re-format and then retry and I for ignore-and-continue. Of course, choosing the latter will leave holes in your written image. As I'd mentioned, and as seen above, the errors weren't always perfectly aligned, but they were not stopping, so yeah, unfortunately that disk was trashed. I wondered if it could be cleaned (Herb Johnson has some tips)? Or if it's totally scratched up... or if you can even replace the medium inside? I tried a bit of isopropyl on it, as I'd done with the drive heads, but it didn't many any huge difference.

Just for fun, I thought I'd test the A-Train Disk A that I'd written to a blank disk. It booted fine, and that's when I realised I had options: leave the 'backup' disk in the box and don't touch the original?, try and transfer outer disk labels?, try and transfer inner disk guts? Hmmmm....

Re-sleeving or Re-mediuming a 5 1/4" Floppy Disk

This was super-risky. I had a properly-copied version of disk A on a (lol) Microsoft Works disk.. and a dead original disk. What to do? Pry open the original and swap the medium. First? Get out your Swiss Army Knife and perform surgery...

Once you have the top broken open, do the same with the donor disk... being super-careful the whole time and remember: DON'T TOUCH THE MEDIUM.

Looking at the old medium, you can see why it was never going to work (and also really hard to photograph):

With everything out, just slot the new medium into the old sleeve and apply a TINY bit of glue along the seam you previously split open. And then?... test...

Shit photos, I know... the game also seems to have shifted into a new resolution/mode and it's interlaced itself off the screen. Whilst my SCSI adapters are in-transit, I'll have to work out a proper video solution.

Update: Learn all about how to get proper video output here.