FDS Error 20

[readry]

Hi, I purchased a Disk system that is apparently new old stock. At least it seems it was newer used. It still had the original batteries from the 80s inside and no signs of use.


Anyway after finally getting the belt replaced and working without it slipping off (was quite annoying), I got it to read a disk.

The problem is, after it finishes reading the disk, it shows "ERR.20". 

According to the sticky thread here, it means "Screen data differs". I did some more digging and the original japanese description is 許認画面のデータが異なる
This roughly translates into "Licensing data is different". According to a japanese website, the cause is apparently that the licensing file can't be read correctly.  This website explains the file system. 

So I think it might be caused by a corrupt disk. Is this possible? Or could the firmware be broken?
Unfortunately I currently don't have another disk to test and I would like to avoid wasting money on another.

Did anyone experience this error before?

[zmaster18]

This error is in fact unusual. Usually error 21, or 27 are the general errors we get for calibration issues. This sounds like it could be a game disk issue. We need to ask a few more questions before we do anything else.

What game have you tested in the disk system? Some games are actually more prone to problems than others.

[readry]

I tested  Konami Icehockey (アイスホッケー) KDS-HOC

Visually the disk looks flawless. The magnet disk itself is clean but has two very, very fine stripes that look brighter than the rest when reflecting light of it. It doesn't look like a scratch tough.

[Retrospectives]

There are some options for this problem to occur. 1: The disk is corrupted by X-reason. Might be because dirt, just became old and lost data, or similar. 2: The reader head of the floppy might be dirty. 3: Other causes such as belt adjustment and such things.

My advice: Do not try to insert another disk. In fact, if the drive head was already damaged because dirt, it might even have been the cause of the "very fine stripes" as you say. Bad reader heads = very dangerous. So try to clean that with a cotton stick and alcohol, but be careful. Do it in forward-backward motion rather than side to side. Be very careful as this is a vulnarable part of the FDS.

This you do Before anything else. On your risk you can try again with the Ice Hockey disk. But since it might already have been corrupted by faulty/dirty drive head, is more good using another known to working disk.

But if that is your only disk, then try to clean the reader head of the FDS unit and if any black or miscolors come to the cotton stick, it is likely to be the reason and is always better to clean head drive before trying with different disk because it might destroy that disk too.

My English is not perfect, sorry about that but as a general rule, please google on how to clean floppy disk head. Preferrably 5.2 inch floppies should have accurate information about how to clean. This is Mitsumi Quick Disk based system 3" but same logic applies, just follow a tutorial and carefully do it. Then please come back and tell us the result if any other problem occured.

Thanks and good luck!

[readry]

Thank you for your advice.

I cleaned the head with a cotton swap and alcohol before I inserted the disk for the first time already. There was no dirt on the cotton swap. As I said, the system was likely never used and sat in the original box for 30 years.  

Since the disk was cheap and doesn't read, I will try to clean the disk. I read several methods. One involved a soft cotton pad and alcohol the other one was soapy water (sounds crazy but since the disk is most likely broken, I don't mind trying it).  

I'm new to the disk system but in my research I read that it's apparently very fragile and often disks can not be read by every drive.

[P]

Correct me if I'm wrong but it should probably be 許諾 intead of 許認. It's the "KYODAKU-" file (means approval) present on every commercial disk that the FDS failed to read. It contains the text data for the license message that scrolls up when you start every commercial FDS game (This title is licensed by Nintendo bla bla bla...).

FDS errors can be quite unreliable, but I also think it could be a dirty, corrupt or broken disk in this case. Or you might still have adjustments to do with the belt and stuff. Power failures can also result in random errors so make sure you are using new quality batteries.

Was the New Old Stock batteries still intact without leaking?

[readry]

Correct me if I'm wrong but it should probably be 許諾 intead of 許認. It's the "KYODAKU-" file

I just copy and pasted the japanese text from that website. Maybe the author made a typo.

Was the New Old Stock batteries still intact without leaking?

Surprisingly they didn't leak. They looked brand new but with an expiration date of 1986.
I didn't test their voltage but they felt light, so I guess they were discharged and didn't even try to use them.

What kind of "belt adjustments" do you mean?

[Retrospectives]

Correct me if I'm wrong but it should probably be 許諾 intead of 許認. It's the "KYODAKU-" file (means approval) present on every commercial disk that the FDS failed to read. It contains the text data for the license message that scrolls up when you start every commercial FDS game (This title is licensed by Nintendo bla bla bla...).

Correct. I would say 許認 = Accept/Acess 許諾 = Admit/Approve but almost same thing. I think he used Google Translate but it should be understood as you described it. In English it would be almost interchangeable if not being too picky about language haha.

Seems that the FDC cannot access that certain file, and therefore any file at all. So best bet after read what he wrote would trying to use another disk. Personally I really not like Mitsumi Quick Disk for the reason it doesn't access data/sectors as traditional floppies no matter 8", 5.2". 3." and later 3.5...Besides FDS, a few Keyboards (Musical) and rarely on MSX + a few other systems it never catched on...and there is a good reason for that. Just too bad Nintendo chose this format, but I guess it was cheap and somewhat reliable of time being and I don't think they had in mind we played this system 30+ years later. 

[P]

I'd think 許認 would be read as kyonin rather than kyodaku like 許諾 is, and I couldn't find it in the dictionary either. I guess it's an existing word anyway though.

The reason I thought that the disk is dirty, corrupt or broken is because I think error 21 ("*NINTENDO-HVC*" string not found) or error 22 (block 1 not found) is more common when FDS is unaligned, while it might be enough that even one letter in the kyodaku file is wrong for error 20 to happen. I'm not really sure though and the errors are known to be quite unreliable for diagnosing.

What kind of "belt adjustments" do you mean?

I just meant what Retrospectives stated in point 3. I don't have any experience of FDS adjustments unfortunately so I can't help you with this part.

[Retrospectives]

I think this is the best English language tutorial I read about adjustments of both driver head and other things:

http://www.famicomdisksystem.com/tutorials/fds-repair-mod/belt-replacement-adjustment/

This takes me back. I remember trying to re-calibrate an old 5" inch floppy which basically ate (really, it chewed them apart almost). Turns out I had driven the manual controlled driver head up for too high speed + a dirty head = total mess. Many year ago now though but I stay away from floppy as much as possible if not totally necessary as for dumping floppies etc.

What type of belt did you use? In Japan we use mobilon made belts. That is probably best option ever to these old floppy drives. But I think really you should not mind about the disk controller itself. At least not now.

I'd think 許認 would be read as kyonin rather than kyodaku like 許諾 is, and I couldn't find it in the dictionary either. I guess it's an existing word anyway though.

The reason I thought that the disk is dirty, corrupt or broken is because I think error 21 ("*NINTENDO-HVC*" string not found) or error 22 (block 1 not found) is more common when FDS is unaligned, while it might be enough that even one letter in the kyodaku file is wrong for error 20 to happen. I'm not really sure though and the errors are known to be quite unreliable for diagnosing.

I don't have service manual for the FDS but provided the link he was posting on topic:

http://park19.wakwak.com/~fantasy/fds/error/error.htm

It describes in detail what might cause Error 20 and beyong, and basically it can mean = A lot of different things. So yeah, is very unrealiable to just go for error codes.

[readry]

What type of belt did you use? In Japan we use mobilon made belts. That is probably best option ever to these old floppy drives. But I think really you should not mind about the disk controller itself. At least not now.

Cheap transparent ones, got them from yahoo auctions. If there was some misalignment or calibration issue, I think there would be another error.

[P]

As the site in the link that Restrospectives posted describes, any error from 20 and upward could mean adjustment problems. The only way to know in your case is to try other disks.

Also power suply problem seems to be the most random of all. It should spit out a battery error but it doesn't always do that. Make sure all your batteries are new and of the same maker. Cheap batteries is also a common problem for the FDS, if nothing else works try another good quality battery maker.

I'd think 許認 would be read as kyonin rather than kyodaku like 許諾 is, and I couldn't find it in the dictionary either. I guess it's an existing word anyway though.

The reason I thought that the disk is dirty, corrupt or broken is because I think error 21 ("*NINTENDO-HVC*" string not found) or error 22 (block 1 not found) is more common when FDS is unaligned, while it might be enough that even one letter in the kyodaku file is wrong for error 20 to happen. I'm not really sure though and the errors are known to be quite unreliable for diagnosing.

I don't have service manual for the FDS but provided the link he was posting on topic:

http://park19.wakwak.com/~fantasy/fds/error/error.htm

It describes in detail what might cause Error 20 and beyong, and basically it can mean = A lot of different things. So yeah, is very unrealiable to just go for error codes.

If we ignore the fact that error 20 can mean lots of other things, I intepret the description in that page as some of the kyodaku data is different from the copy of it in the BIOS (that the BIOS uses to compare the two). Meaning it probably finds the kyodaku file on the disk but if even one letter is wrong (due to dirt, scratches or demagnetisation of the disk) it refuses to load the game and spits out error 20.

The BIOS has a copy of the licensing text data (the one that scrolls up when starting an FDS game) in the kyodaku file and requires every FDS disk to have a kyodaku file (the file name can be anything but most games names it "KYODAKU-") with the exact same text in order to start. This is to legally prevent certain (especially Taiwanese) unlicensed makers from developing games without a license for it. It's the same reason why every Game Boy game needs to have the graphic data for the Nintendo logo that scrolls up when starting a Game Boy game. Although there are actually ways to trick the BIOS in both the FDS and the Game Boy so you can start without having this data.

[Retrospectives]

The BIOS has a copy of the licensing text data (the one that scrolls up when starting an FDS game) in the kyodaku file and requires every FDS disk to have a kyodaku file (the file name can be anything but most games names it "KYODAKU-") with the exact same text in order to start. This is to legally prevent certain (especially Taiwanese) unlicensed makers from developing games without a license for it. It's the same reason why every Game Boy game needs to have the graphic data for the Nintendo logo that scrolls up when starting a Game Boy game. Although there are actually ways to trick the BIOS in both the FDS and the Game Boy so you can start without having this data.

Yes, is true. It can and it was hacked serveral time so that's why Nintendo released a modified rev of the hardware replacing 7201 with  3206  controller chip. So many people nowadays got problems especially using the FDS Stick or other external hardware to access to write/read they needing modding their FDS systems or else it cannot work unless they had old revision (I forgot exact date).

But judging of topic, his system seem to come be in very good condition, so probably the disk is faulty and should at least try with another disk. I mean, they are so cheap it would be more risk to take system apart again and maybe damage something rather than just buy another but known working soft haha. 

[readry]

Good news. The disk system works perfectly.
It was the disks fault after all.

I tried  it with a known working copy of Kalin no Tsurugi SQF-KRN.

[P]

Good to hear and thanks for reporting.