Famicom Disk System - alignment specifications?

[RetroHacker]

First time poster, long time lurker...

I've recently acquired a Famicom Disk System, and like all the others, the belt was bad. I bought a new belt online, and followed the instructions in replacing it. And I'm having the same problem that just about everyone else has - I can't get the thing aligned. I've actually gone through and rotated the spindle hub in tiny increments, a full 360 degrees. And I still can't get anything to load. Error 22, Error 21, it varies, depending on how I have it set. I've even gotten an Error 23 once. But only once.

The spindle turns freely, the belt stays on and does not appear to slip. It's the right belt even, not just some random one that fits, ordered from a seller specializing in game console parts.

Now, I have a lot of unknowns here - I only have the four disks, and I have no idea if they are any good.

What's frustrating to me, is I can find no real technical data on how the mechanical portions of the disk drive work. I found information on the data protocol, but nothing about the drive itself. Like, for instance, what speed is it supposed to run at? What is the proper starting position for the head and the disk media?

What about other things - like, how critical is the alignment of the limit switch? I haven't messed with it, although I did have to remove the board to change the belt. When I put a disk in, the head moves forward slightly, retracts back and hits the stop, then scoots forward a bit. The disk and head both stop, then it reads forwards. Is it supposed to scoot forward before stopping like that, or is it supposed to stay back until it has to read the disk?

I have no doubt that my problem lies in the relative positions of the gears that move the head assembly, but what's the proper procedure for aligning them? There are some holes on the spindle wheel, and the metal cam, I can't help but think there's a jig for aligning them, or a diagram (with measurements) of how they're supposed to align. For instance, complex gear train assemblies in some printers come with holes in some of the gears, you pin the gears together with a paper clip to keep them aligned while installing, and align the holes with scribe marks or holes in the frame.

Any advice would be greatly appreciated.

-Ian

[Frank_fjs]

Hey Ian,

Too late for this but I will give you one very important piece of advice for the future - do NOT adjust the spindle hub in any way! I know what the internet tutorials state and I too believed there was some mystical spindle alignment procedure required, but I've since learnt (through others who repair these things daily and through restoring half a dozen of them myself) that this is a big misconception. The height of the spindle is the only important thing and if left as it was set at the factory should never have to be adjusted.

To get your disk unit working you will need to adjust the magnetic head adjustment screw. It's a spring loaded screw and in most cases will need to be tightened a little. Keep tightening this screw in small increments, test, rinse and repeat until you finally see disks start to load.

The only other adjustment you may need is to adjust the motor speed. Do this via a small flathead screwdriver, there's a small hole on top of the motor covered with a rubber like flap. Just push your screwdriver through this flap and gently turn to the right to slow the motor down and to the left to speed it up. In most cases you will need to slow the motor down a little.

Good luck with it, just be patient and you'll get there. Shout out if you have any further questions/require more assistance.
Post Merge: November 20, 2012, 08:46:38 pm
P.s. There's no such thing as the right belt, but I would still be interested to hear where you're getting yours from.

Also, in regards to this:

When I put a disk in, the head moves forward slightly, retracts back and hits the stop, then scoots forward a bit. The disk and head both stop, then it reads forwards. Is it supposed to scoot forward before stopping like that, or is it supposed to stay back until it has to read the disk?

When everything is working as intended it's not supposed to stop as you described. It should move in one clean motion without stopping until it hits the end of the read cycle and snaps back to the starting position.

[RetroHacker]

No, I do not know if my disks are readable. While it's theoretically possible that all four are bad, I'd have to think one would at least load part way. But, then again, I'm just going on my prior experiences with computer floppy disks.

I'm trying to avoid making adjustments to the head screw or the speed - I mean, since those were never messed with, they ought to still be close, right? Especially since the head adjustment screw is held together with glue. The only thing I did muck with was the alignment of the gears and the spindle, since I had to disassemble it to replace the belt. Basically, I want to avoid making any blind adjustments without clear reason for doing so. No surer way to really mess up a piece of equipment than to go blindly fiddling with all the adjustments.

-Ian

[Frank_fjs]

I'm trying to avoid making adjustments to the head screw or the speed - I mean, since those were never messed with, they ought to still be close, right?

It's not that simple. The motor may have weakened with age. The new belt you fitted is not to the same specification as a genuine Nintendo belt, it may be looser or tighter and/or have different elasticity. You're basically starting from scratch. You need to tune the system to it's newly altered state. This isn't the type of device that has a one size fits all range of adjustment. Even when new, straight off the factory line, each unit would have been tuned differently. No two units have all screws in the exact same position.

The only thing I did muck with was the alignment of the gears and the spindle, since I had to disassemble it to replace the belt.

The spindle is the one thing you shouldn't be touching and the head screw/motor speed is what you need to adjust. Now that you've already messed with the spindle you may have to adjust that back to its correct height and co-ordinate this with the other two forms of adjustment.

No surer way to really mess up a piece of equipment than to go blindly fiddling with all the adjustments.

Well the piece of equipment is already messed up, is it not? It's not performing its intended function which is to read disks so what do you have to lose?

There is no factory specification or manual that we can follow, there's no magical guide with precise, guaranteed measurements. The reason that people are able to restore these things without official instruction or guidance is because they were willing to experiment and learn.

You will never get it reading disks until you adjust that head screw. Motor speed will most likely be fine but there are some cases where some slight tweaking will be required.

I got one going just the other night. After fitting the new belt and not touching the spindle in any way, it took all of 2 minutes to get it reading 20+ disks with 100% reliability.