need help: yamaha floppy disks interface fd-501

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By amerklm22

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01-07-2019, 11:42

I have yamaha floppy disks interface fd-501 cartridge laying around but i dont not have the drive that came with. I was wondering would it be possible to attach it to a typical floppy drive and use it
this is the one i have FD-501
i have 2 msx machine
msx ax-170
msx ax-230

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By Wild_Penguin

Hero (538)

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01-07-2019, 14:07

From your link we can find the service manual.

From the service manual, it looks like the interfcae has a 40-pin connector (for the cable going to the floppy drive), can you confirm this? (EDIT: It might be the extra 6 pins mean the floppy side coming from the PSU, and the service manual just is not clear enough here. There is another pinout later, but it is conveniently partly cut out from the scan!)

The pinout is on page 17 (it's description is a bit weird, seems like there are two pins of each signal and only 2 GND - but I suspect every odd pin is GND, which is easy to check with a multimeter). If that (GND at odd pins) is correct, seems you are in luck; by a quick glance, it is identical to Shugart pinout, except the extra pins, which have +5V and +12V. That should be fairly easy to adapt to connect to any Shugart (or PC) compatible disk drive. Compare the pinout here.

The problems to consider are: 1) all PC drives are "drive B: / DS1 activated" per default. And 2) Ready signal. The latter depends on the ROM in that (FD-501) interface. Also, 3) HD-compatible disk drives can be used, but you need to deal with the HD-sensor in some way (cover the hole on your disks is the simple remedy for this).

EDIT: In this case, power is another concern. Looks like the original drive was connected to mains separately. Moreover, most modern floppy drives use only +5V. I don't think the interface/MSX slot/your MSX can provide enough current trough the +5V, at least not safely and for prolonged time!

If you can use a multimeter and understand what I've written above, I believe you are probably up to the task. If you are uncertain, just ask here, maybe we can still walk you trough it!

Good Luck!

By Alexey

Guardian (2159)

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01-07-2019, 16:39

If I remember correctly, you need either the original DS/DD drive or a PC drive with DS0 setting and configured to work in DD mode. If HD diskettes are used with PC drive, the HD hole need to be covered with a tape. And of course you will need the separate power supply for the diskette drive.

By amerklm22

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01-07-2019, 17:11

thanx for your replay it look like the service manual is different from my cartridge
the cable is 34 pin . and after i check with multimeter
the pins 1-2-3-5-7-9-11-13-15-17-19-21-23-25-27-29-31-33 are all GND
so what next?

By Wild_Penguin

Hero (538)

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01-07-2019, 17:48

I think the service manual is correct / identical. It's just that part is a bit unclear. The extra pins represent the power connectors (and might be more correct with the original floppy drive; perhaps it had internally a 40-pin connector).

You need a straight 34-pin flatcable (floppy cable "without twist"). You can make your own, too, or use a PC floppy cable, but you need to use the connector which is not after twisted part and configure the floppy as DS0, as Alexey said (many, but not all, PC floppy drives have a jumper for this - either with jumper caps or with solder). After that, it could "just work" - provided you give power from an external power supply.

Most MSX DiskROMs don't care about Ready signal, though I'm not sure about this case. Perhaps someone else knows for sure...

By amerklm22

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02-07-2019, 13:26

i have PC floppy cable same as this one i cut the twisted part and resolder it again is thats ok ?
now about converting the floppy to DS0 how to do that ? i have sony model mpf920-1 is this what i have to do?
i done that but didnt work also it damge the floppy disk

By Wild_Penguin

Hero (538)

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03-07-2019, 11:58

No, don't look at Amiga instructions. Amiga disk interface is not identical to Shugart (PC drives kind of are, see below).

Don't cut the flat cable. You can not solder a flat cable (well, you kind of can but it makes no sense in this case). Either get another floppy cable which has a connector in the straight part (meant for drive B) or crimp on a new connector to that kind of cable you have pictured (you don't necessarily need the crimp tool, although it makes the process a lot easier; just make sure you press straight on the connector parts with something - and take your time; it should go in eventually). Of course you could make the changes by cutting the floppy cable and soldering, but IMO that makes no sense - that is only another place of failure (twisting the cable -> broken solder point - or shorts) and crimping another connector is a lot easier (or just get a ready made cable, since they do exist).

Also, before you do anything, an advice based on experience: check on a PC that the floppy drive you are working on still works properly. I've had some hairs pulled out trying to get a floppy drive work on my MSX, only to find out the drive was just plain faulty to begin with. These drives are old (and that particular model, being the newest ones ever made, their built quality might actually be worse than those made in the 80's and beginning half of 90s!)

Look at the pinouts. PC pinout differs from Shugart in the following way: PC has separate motor on and DS signals for drives B and A. PC drives do not need jumper settings but which drive is A: (after the twist) or B: (before, i.e. straight cable) is selected by twisting some of the pins in the cable - i.e the pinout on the PC floppy drive is always the same. This also means PC drives are always almost compatible with a drive selected by /DS1 (per Shugart interface) with a straight cable. (not accounting /RDY signal!). See: https://superuser.com/questions/849079/what-is-the-little-tw...

So: A PC drive connected to a Shugart compatible floppy interface (which includes the one you have) should work as "drive B:", but many disk ROMs will not look for drive B: (/DS1) if A: (/DS0) is not present.

This means: you can connect up to 2 drives to the same cable, if one is jumpered as /DS0 and one as /DS1 (= just a regular PC floppy drive). As you can see from the previous link (earlier in this thread), there are also /DS2 and /DS3 pins, but AFAIK no MSX disk interface ROM (and/or controller) can use them - but in theory, you could have up to 4 drives hooked up this way!

So, the only change you (probably) need to do, is to move the /DS1 jumper to position /DS0. You can check you have made the correct modification, by checking with a multimeter connection to the jumper; before you do anything, the trace should connect to pin 14 (corresponding to PC Drive A: select; and /DS1 in Shugart); after moving the jumper it should connect to pin10 (corresponding to Motor A on a PC; /DS0 in Shugart).

That's all! Well almost, there's still the Ready signal, but changes are you don't need it! Although the service manual lists it in the pinout, there is a high change it is not actually used (EDIT: they probably just copied Shugart pinout here, since that's what it essentially is).

Most MSX Disk ROMs don't care about Ready signal (but, I've red, some do!). PC drives don't provide Ready signal, but have /DSKCHG there instead. Some have jumpers to change that. I believe your driver doesn't have one (you can check yourself, if there is RDY or Ready jumper somewhere, it's there)! Point being: if the drive still doesn't work after changing /DS1 -> /DS0, the interface might still require the ready signal. As that signal is active low, you can short the signal with GND (although now it is "always ready", it does not cause problems, I've been told!). You can do this on the drive or on the cable (I'd prefer the drive, as it has a nice PCB, where it is easy to also undo stuff if needed) or even on your floppy interface cart (but that's the most expensive part here!).

Cheers!

P.s. IIRC Amiga drives expect /DISKCHG signal at pin 2, and don't use RDY at all. But I could be totally wrong, one needs to check their documentation to be sure. Lesson to learn here: first understand what you are doing and then make the modifications - don't just follow walktroughs blindly!

By amerklm22

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03-07-2019, 17:14

thank for your help finally its working . the sony floppy driver didnt work idont know why but its woking on pc
i found older one TEAC floppy and it works from first try
thank you agine

By amerklm22

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03-07-2019, 19:43

one thing about the ready signal how to short the signal with GND
what pin is ?is it pin 34 to GND ?

By amerklm22

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04-07-2019, 12:22

i tryed some games but didnt work the msx reboot while loader disk but other game working fine
games like
Crusader
The Castle
Castle Excellent

By Wild_Penguin

Hero (538)

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05-07-2019, 16:15

amerklm22: I believe that means the disk drive works fine! It either works fully or doesn't work. It won't cause reboots.

Which MSX are you using? Which games cause crashes?

Note that you have MSX(1) machines, MSX2 games might give a nice message they wont work on an MSX1, or crash / reboot. Also some games, especially cracked ones (which were not originally released on floppies), might need more RAM. Again it's the same thing - if the programmer decided to put in a check and a message or not. In the latter case, the result might just be a reboot/crash...

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