Famicom Disk System Head Adjustment - FIXED

[InsaneDavid]

I recently replaced the belt in my Twin Famicom using the tutorial at jfgoods.net (http://jfgoods.net/disksystem.html). I put it all back together and had the usual success running my lone FDS game. Of course there were missreads here and there but I know that's part of the system and after a couple eject and reloads things were fine. However performance began to get progressively worse until I can no longer get the game to load. Error 27's and now error 21's up the ass. Every time - error 21.

I've run the drive with the case open and it appears as if everything is working right. Once a disk is inserted the head slips back to the outer edge of the disk, trips the switch, the drive resets (read light off / light on) and then smoothly moves back toward the center of the disk. It then retracts and tries again and that's when I get the error 21.

I'm curious if I have the disk set misaligned. The walkthrough above doesn't make it all that clear how to get it set right. From what I've gathered you turn the large gear wheel clockwise (looking at it from the bottom) until it will no longer turn. Then you loosen the set screw on the disk set, rotate it so the set screw is facing back at the head, then tighten it back down. The big thing I don't understand in the instructions is the difference in position of the disk set between pictures 41 and 42.

Can someone who has a properly tuned FDS take a picture of their drive in the default power off starting location of the disk set with the card holder removed? Am I missing a step somewhere or is there something I don't have set right? Something else to try? Any help would be great. Again, it did work after I changed the belt but has progressively gotten worse until now where I get an error 21 every time. Media is official Nintendo.

[Frankie_Says_Relax]

When I first replaced the belt on my FDS (standard one) I got Disk Error #21 on everything I put in there ... it was only after I reset the head according to the diagram on JFGoods.net that I saw any success in getting things to load. And it sounds like you did it exactly as they described.

I did notice the difference in the head location between those two photos, but I just left it at the far end of the track (where it stopped moving) when I put it back together. I didn't spin it back to the other end.

The F1 disk I sent you was one of the disks that I tested ... and I never got any read errors while using it, so I don't THINK it's the media ... but you know how these things go, especially 20+ year old magnetic floppy material ... you might want to get your hands on another game or two to see if it is in fact the system causing the read errors or the game itself.

Also, take a look at the head and make sure it's free of debris. I think I cleaned mine off pretty well while I was getting drive belt gunk off of everything.

[InsaneDavid]

Thanks for your replies (both here and via PM). At this point I'm convinced that I have everything adjusted properly, it just seems like everything is set properly. I'm going to assume the disk card has gone bad / was going bad (maybe due to transit) since I was getting error 40's here and there when things were working earlier - as well as scrambled error screens between in game loading. I'll have to try another disk so I don't think the errors are any big deal.

[Frankie_Says_Relax]

Crap ... sorry man.

That was my only duplicate Fami Disc, or else I'd send you another to mess around with.

[madman77]

In addition to the head alignment, which it sounds like you've done properly, there is also a speed adjustment for the drive motor. Too fast or too slow and you will get errors. The only way to know for sure if your speed is adjusted properly is to have a game doctor + copy master. I've got 4 FDS drives that I've aligned and tuned and there isn't a single disk they won't read correctly, even pirates.

[InsaneDavid]

Crap ... sorry man.

That was my only duplicate Fami Disc, or else I'd send you another to mess around with.

Don't worry about it, thanks again for your help and for the F1 Race disk!


In addition to the head alignment, which it sounds like you've done properly, there is also a speed adjustment for the drive motor. Too fast or too slow and you will get errors. The only way to know for sure if your speed is adjusted properly is to have a game doctor + copy master. I've got 4 FDS drives that I've aligned and tuned and there isn't a single disk they won't read correctly, even pirates.

I was thinking about that but I'm going to wait until I have another couple disks to try for better diagnostic. I don't mind slowly manually tweaking stuff like that, heck if anything it'll bring back memories of PS1 mod days.

[spoon]

I would say madman is probably right. I was gonna post a response the other day. I have fixed a few FDS' and this is usually the last thing that has to be tweaked.

I've made a few posts about it before, I never knew a game doctor+copy master would help. Wish I would have. I just used the good ole trial and error method.

Good luck.

[InsaneDavid]

I would say madman is probably right. I was gonna post a response the other day. I have fixed a few FDS' and this is usually the last thing that has to be tweaked.

I've made a few posts about it before, I never knew a game doctor+copy master would help. Wish I would have. I just used the good ole trial and error method.

Good luck.

Yeah, my next day off is Monday so I think first I'll do some slight adjustment tweaks to the disk set, 1/8th of a turn here and there, just to see if it changes anything. If I get no change in results then I'll do the full reset calibration (as shown on the jfgoods.net site) again and start tweaking the motor speed.

[InsaneDavid]

Finally had some time to work on this again and I've fixed it. All it needed was some slight adjustment to the disk set. Although I calibrated it properly as per the jfgoods.net instructions, it just didn't look right to me. When the disk would stop spinning (after a load or attempted load) the disk set was turned slightly, didn't seem like that was right. No matter how many times I would recalibrate it, the final start / stop rotation position was always turned just a little. It would always end up in exactly the same place in rotation, turned a little from center.

So I opened up the Twin Famicom, removed the FDS drive, removed the front retainer and the springs that hold the disk card holder down. Then I put the drive back in the Twin Famicom and reconnected the I/O cable and the ground connection. This way I was able to make slight adjustments to the disk set, put the disk card holder back on, insert a disk, apply slight pressure to the disk card holder with my fingers (to simulate the springs) and view the results. After a couple slight trials I figured I'd rotate the disk set to where it seemed logical that it should rest. Tried it out and bam - zero errors and two second load times. Reassembled the drive and Twin Famicom properly and it's working like it was brand new.

Here's a picture of how my disk set is positioned when the drive is at rest (ready to accept a disk / finished with a read)...

http://www.classicplastic.net/digitalpress/TwinFamicom01.jpg

I don't know why the recalibration in the tutorial didn't work for me, perhaps I was turning the gears too far when I was feeling out the adjustment point. Either way, it makes more sense to me to adjust the disk set when the drive is spun down into this position. I'm going to assume that every one of these drives may be just a little different and require some slight adjustment outside the norm.

I knew I was on the right track when my constant error 21 was joined with 22 and 27, that and the black screen would come up just before then. It was doing something different, my adjustments were changing how the drive saw the disk, progress was being made. Heck, side B was even giving me the error 07 again, so I was almost there. Then after that final adjustment, instant loading.

http://www.classicplastic.net/digitalpress/TwinFamicom02.jpg

Woohooo. :) So if you have an FDS drive that seems to give these errors when you seem to have calibrated it as instructed, try a couple small adjustments and some trial and error. I never messed with the motor power control, didn't need to.

Thanks again for all the help!

Oh, and for FDS horror stories, Frankie told me about loosing one of the disk card holder springs and having to spend a considerable amount of time looking for it. While just before my final adjustment I dropped the disk set setscrew... out in my shop... at one o'clock in the morning. I did find it though, bounced under my workbench. LOL Was really sweating it for a moment there though.

[Frankie_Says_Relax]

CONGRATS MAN!

\\^_^/

Glad to see you got it all working ...

Enjoy that F1 Race!!!