Some games not working on my FDS.

[BravesFan1966]

A couple of months ago, I bought a Famicom with its disk system. When we got it, the store I bought it from told me that the guy who sold it to them said that it had had some problems. I am fairly sure that he said the belt was replaced. It has been very hit or miss, it will play all the games for a day, and then it won't work for a month. This was weird, but recently it has changed. One of my games will play, an official copy of Doki Doki Panic. One of my games only works on side a, a reprint with all-night Nippon smb on side a, and smb 2 Japan on side b. Finally, my other game doesn't work at all, an official copy of the Legend of Zelda. Also, when I try the Zelda disk, it gives me three different error messages each time I try it: 21, 22, and 25. I'm very confused , any idea what's going on?

[Skawo]

Probably a miscalibrated drive. Could also have speed problems based on how it sometimes works and doesn't.

[BravesFan1966]

Thank you so much! I'm new to the mechanics side of things, any idea what I would need to fix it? Or if there was somewhere I could send it to get it fixed, because I really don't want to mess up and break it.

[Skawo]

The process is described here in the Spindle Hub adjustment section:
https://www.famicomdisksystem.com/tutorials/fds-repair-mod/belt-replacement-adjustment/

And, well, I'd be willing to do it for you, but I imagine you don't want to send it halfway across the globe, so, :v

[BravesFan1966]

Ok, thank you so much, I think I'll attempt to do it with my uncle, I don't trust shipping services, especially since things will get damaged going halfway across the city.

[P]

You would also need an oscilloscope and a logic analyzer or you will only get some disks to work.

Where are you at? If in America there was another guy offering this service here.

[Skawo]

I dunno about _need_, it's not THAT precise :v
I think the oscilloscope is only really needed to make sure your FDS writes disks properly, you should be able to get it to make it load games just with a basic spindle/speed adjustment.