Why are Famicom Disk Systems so picky?!@...

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

Moderators: B00daW, Moderators

Post Reply
DrWho198
Posts: 25
Joined: Mon Feb 23, 2015 8:05 pm

Why are Famicom Disk Systems so picky?!@...

Post by DrWho198 » Wed Feb 14, 2018 1:00 pm

Why are Famicom Disk Systems so picky compared to other disk drives. Let's be honest, many computers have been using different kinds of disks and none of them showed a compatibility problem between written disks that were written on other drives of the same kind. Why is the FDS so different? One key factor could be age and repairs. If they are badly tuned then it might cause some issues. But besides that I see no reason why they should be so sensitive.

Does anyone have more reasons why the FDS is the exception.
And what tools and methods are the best to solve timing and alignment problems when you repair a FDS.

tepples
Posts: 21971
Joined: Sun Sep 19, 2004 11:12 pm
Location: NE Indiana, USA (NTSC)
Contact:

Re: Why are Famicom Disk Systems so picky?!@...

Post by tepples » Wed Feb 14, 2018 4:27 pm

One issue is that because the Mitsumi Quick Disk transport is so uncommon, belts and other replacement parts were never mass-produced to the same extent as with the standard 3.5" floppy. Another is the spiral track. Unlike traditional 5.25" and 3.5" floppies, which lay out data in discrete tracks and sectors, the Quick Disk uses a spiral track similar to that of vinyl records, CD, and DVD. Its head needs to stay centered over the data continuously throughout the entire run. And I'm assuming it would have been too expensive to use the 3-beam centering mechanism that optical pickups use. Optical pickups use the center beam for reading data and two beams placed slightly inward and outward for determining whether the signal would be stronger if the read head moved slightly inward or slightly outward.

DrWho198
Posts: 25
Joined: Mon Feb 23, 2015 8:05 pm

Re: Why are Famicom Disk Systems so picky?!@...

Post by DrWho198 » Wed Feb 14, 2018 5:13 pm

Well, that does make some sense.
If I'm not mistaking (I'm new to the fds world) then hacker included a tool in they're backup software to align the header. How effective is this or is there a better way?
Because given the information that was discussed so far, there is no reason why a correctly aligned drive with a new belt wouldn't read/write perfectly. The only problem could occur when the drive was moved rufly or the belt stretched to the extent that it slips.

Another question that comes in my mind is;
Are the drives in the famicom disk writer that were in the stores different from the ones in home units. If not then a blue disk or in-store rewritten yellow disk would have no better quality then the home written ones on a well aligned console. Which should have an impact on the value of those disks.

User avatar
koitsu
Posts: 4217
Joined: Sun Sep 19, 2004 9:28 pm
Location: A world gone mad

Re: Why are Famicom Disk Systems so picky?!@...

Post by koitsu » Fri Feb 16, 2018 1:38 am

I agree with Tepples. Expanding on it a bit more, as well as presenting my own opinion:

The drives use a very specific kind of belt, made from a somewhat odd or unique rubber (or rubber-like mix), and are *extremely* sensitive to belt length, belt tension, any cruft/junk on the belt motor (this can happen if/when replacing an old belt), etc. -- all which affects overall timing (and you already know what happens if you get this wrong). Replacing belts in the FDS, as I recall, was a common thing. So a lot of FDS drives start acting wonky because of the belt. Can we agree on that?

What affects the belt tension, length, etc. over time? Lots of things -- one of which is heat. I speak from experience on this one. The very first FDS I ever had was given to me by a friend living in Japan who found it in a storage closet of a small company he was working for. Once I got it and confirmed it didn't work (always got an error when reading from disks that were definitively good), I opened it up and found the drive belt had literally melted sometime long in the past. It wasn't goop -- it had melted and become rock hard, and was all over the inside of the system. Cleaning off all the residue was difficult, but even after I did so and replaced it with a supposedly authentic belt, it still didn't work. Adjusting some of the timing pots didn't help either (and I didn't want to mess with those too much anyway, it can actually make things worse if you don't know exactly what is wrong with the system. It's better to leave them alone!). I ended up giving said FDS to Matt Conte (of Nofrendo/cajoNES/nes6502/Nosefart fame), saying "it's yours, I hope you can fix it!" Unsure if he ever did. I got a new FDS sometime later -- same disks, works fine.

Another thing that certainly would affect the belt would be humidity and environmental changes (consider moving from, say, Okinawa (warm part of Japan's southwestern islands) to Hokkaido (cold part of Japan)). You've also got "general environment", like where people placed the FDS in their homes during use, if they left the system on for long periods of time (internal heat), etc.. Japanese homes are not known for being spacious, things tend to be optimally positioned/placed to fit perfectly in small nooks and crannies.

This might help explain why Disk Writer kiosks seem to be of "better quality". Were the drive drives in said kiosk *actually better quality*, or is it simply that the kiosks resided in department stores which were air conditioned (proper humidity/temperature balance), thus the innards lasted longer? Maybe they WERE better quality -- the only way to know for sure would be to have an actual hardware engineer do a teardown of both a Disk Writer kiosk as well as an FDS and provide an analysis. Anything else is purely speculative/anecdotal (including my own above theory). The closest I've seen to such is this article from Chris Covell, which has a photo of the innards, but the disk drive appears to be enclosed in a metal box.

My $0.02, likely not worth much.

DrWho198
Posts: 25
Joined: Mon Feb 23, 2015 8:05 pm

Re: Why are Famicom Disk Systems so picky?!@...

Post by DrWho198 » Fri Feb 16, 2018 2:19 am

Thanks for the link, I didn't know about that one yet.

About the belt problem, you seem to assume that the fds is picky about the belt. Which might seem like it, but I don't see why it would be any different from any other belt driven device. Problems with belts are that they can slip, dry out, get affected by moisture or stretch and shrink. Slipping is generally the problem if the belt uses a material that doesn't have enough grip or when the size of the belt is off. Drying out is mostly a time problem, but climate can also be a problem here. Moisture, stretching and shrinking is also an environmental problem. A stretched belt could slip and a shrunken belt can snap. When the belt gets affected by moisture then it can lose its strength and snap or turn to goo. But all these problems can be improved when the belt is of good quality, and are not FDS specific unless Nintendo has used bad quality belts.
Last edited by DrWho198 on Fri Feb 16, 2018 8:57 am, edited 1 time in total.

tepples
Posts: 21971
Joined: Sun Sep 19, 2004 11:12 pm
Location: NE Indiana, USA (NTSC)
Contact:

Re: Why are Famicom Disk Systems so picky?!@...

Post by tepples » Fri Feb 16, 2018 8:00 am

If Nintendo used "bad quality" belts, it's because Nintendo used Quick Disk, and I'm guessing Quick Disk belts in general were "bad quality" in the sense of not having been designed for the sort of rough service that other Nintendo products of the era withstand.

Fast forward to 2001. By then, Sony Discman and the rise of laptops had make optical disc pickups suitable for rough service. This led to the return to discs in Nintendo GameCube.

User avatar
loopy
Posts: 395
Joined: Sun Sep 19, 2004 10:52 pm
Location: UT

Re: Why are Famicom Disk Systems so picky?!@...

Post by loopy » Fri Feb 16, 2018 11:34 am

When you replace the belt, gear positions get moved and alignment gets out of whack. I think here is where it goes wrong for most people; there's a lot more involved in drive repair than just replacing the belt. Here is the most thorough guide I've seen.
DrWho198 wrote:Well, that does make some sense.
If I'm not mistaking (I'm new to the fds world) then hacker included a tool in they're backup software to align the header. How effective is this or is there a better way?
Because given the information that was discussed so far, there is no reason why a correctly aligned drive with a new belt wouldn't read/write perfectly. The only problem could occur when the drive was moved rufly or the belt stretched to the extent that it slips.
http://www.famicomdisksystem.com/disk-copy/
This talks about adjusting the drive speed, I don't think it helps with head alignment.
I have a debug version of my fdsstick software that does extra analysis for head adjustment, though I've never released it to the public.

Image
Last edited by loopy on Fri Feb 16, 2018 11:53 am, edited 1 time in total.

DrWho198
Posts: 25
Joined: Mon Feb 23, 2015 8:05 pm

Re: Why are Famicom Disk Systems so picky?!@...

Post by DrWho198 » Fri Feb 16, 2018 11:52 am

Do you think you will ever release such a tool that will help us align drives?
Since the drives are getting older and older, chances are that at least half of them are not properly aligned.

that1crzywhtguy
Posts: 1
Joined: Thu Oct 17, 2019 11:56 pm

Re: Why are Famicom Disk Systems so picky?!@...

Post by that1crzywhtguy » Thu Oct 17, 2019 11:59 pm

I also would be THRILLED to have access to such a debugging tool. The game doctors are rare and expensive (very), and other than trial and error there is no way to set drive speed. And as for alignment, in my experience usually the methods online work first try, but also not always. I have 2 drives here that I can't get aligned. I LOVE my fdsstick though!

User avatar
loopy
Posts: 395
Joined: Sun Sep 19, 2004 10:52 pm
Location: UT

Re: Why are Famicom Disk Systems so picky?!@...

Post by loopy » Fri Oct 18, 2019 3:01 am

http://3dscapture.com/junk/FDSStick_debug_20171229.exe

Use a known good disk (written by a properly calibrated drive) for adjusting your drive. Preferably a real commercial disk, not bootleg/copied.
Push the "Test" button to scan a disk. The software shows a graphical representation (blue wavy lines) of data timing, you want to see 3 well defined (tall, pointy, non-overlapping) humps.
The "σ" number shown is a relative measurement of the head alignment (smaller number is better).
Make small adjustments to the head alignment screw (this one). A 360° turn moves the head about 1 full track, so your turns should be much smaller than that. I'd start with 45° adjustments and keep testing/tweaking until you feel like it's dialed in.
Motor speed is less important, but you can tweak that too if you feel like it.

skaman
Posts: 85
Joined: Fri Oct 24, 2014 1:56 am

Re: Why are Famicom Disk Systems so picky?!@...

Post by skaman » Fri Oct 18, 2019 11:02 am

Thank you, loopy!

Post Reply