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FDS Stick: Writing to Disk Issues

Trimesh

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The 3206 mod should have no effect at all on disc compatibility. All it does is disable the write inhibit logic that normally prevents you from rewriting the system area of the disc. I have a couple of drives with the mod that Tomy supplies in them, and they read fine on my systems (including my Twin Famicom). I have seen these sort of problems with drives that have marginal alignment - you can have two drives that both read factory discs with no issues, but neither will read discs that were fully rewritten on the other. The basic reason is that both drives are slightly misaligned, but in opposite directions.
 

BinBowie

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Ah. Is there a way to completely correct a drives alignment or is that uncharted territory?

The whole reason I got the modded system was that I'm hoping to release homebrew on FDS disks sometime in the future. Writing disks that can't be read by some systems poses a problem.
 

Trimesh

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Ah. Is there a way to completely correct a drives alignment or is that uncharted territory?

The whole reason I got the modded system was that I'm hoping to release homebrew on FDS disks sometime in the future. Writing disks that can't be read by some systems poses a problem.

Yes, it's possible to adjust it, but it requires both a disc you know has correct alignment (I.E. a factory written disc you know has never been overwritten) and a scope. You also have to be sure that the basic alignment of the drive is correct (I.E. the head retracts at the start of the spiral - this can be assumed to be true if you can read discs at all).

Once you have the drive hooked up, connect the scope to the pins on the drive PCB that connect to the read head, monitor the signal while reading the disc and gently push the sled in and out - if the alignment is correct, there should be basically no change in the read amplitude. If you find that the signal increases when you displace the head in one direction, then the drive is out of alignment.

This is done using the screw on the back of the head assembly - it's generally locked with something like Glyptal, so clean that off and carefully adjust the screw while reading the disc. You need to find the two points where the signal starts to drop and then set the screw to the middle of that range. Once you have found it, repeat the "push the sled" test and make sure nothing has moved. Then seal the screw (nail varnish works OK) and repeat the sled push test again.

After I went through this process will all my drives I had no further problems either with original discs or the ones I had rewritten. Obviously, it depends critically on how good your original test disc is.
 

Tomy

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Once you have the drive hooked up, connect the scope to the pins on the drive PCB that connect to the read head, monitor the signal while reading the disc and gently push the sled in and out - if the alignment is correct, there should be basically no change in the read amplitude. If you find that the signal increases when you displace the head in one direction, then the drive is out of alignment.

Hi Trimesh,

Can you explain what mean "push the sled in and out" ? Thank you.
 

Trimesh

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Hi Trimesh,

Can you explain what mean "push the sled in and out" ? Thank you.

Hi, Tomy

The sled is the bit of the mechanism that the head is mounted to - normally it's pulled towards the back of the drive using a spring and moved in by the snail cam. So to push it in you just have to (gently) push it towards the front of the drive - to check the other way, hook a wire into the hole the spring is attached to and try to pull it towards the back of the drive.

If the alignment is correct, the signal will drop when you move the head either way from the track center.

Your name seems familiar - you don't happen to live in Sham Shui Po do you? Or am I thinking of another Tomy?
 

Tomy

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Yes, I'm Sham Shui Po Tomy. How are you ?

Thanks for explain. I doing the same as you.
 
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