Modifying PC floppy drives for Amiga use

[Jope]

Originally Posted by paulo_becas

What do you suggest?

There is no really easy way.. If I can't deduce it, then I start poking around for signals that go low soon after the disk starts spinning. :-) Not very scientific, I'm afraid.

[paulo_becas]

Originally Posted by Jope

There is no really easy way.. If I can't deduce it, then I start poking around for signals that go low soon after the disk starts spinning. :-) Not very scientific, I'm afraid.

I've been tinkering with floppy drives for a long time and even the El Piloto's universal mod is not working with a lot of drives then there's the weird things like the mitsubishi drive i've modified that looks like it won't work with the anticlick app.
I think it all depend on the design, we've got one that's very simple and looks like most of us already modified at least one, the samsung SFD-321B, the downside of this drive seems to be the poor construction or poor materials, i don't know
I guess this is not an exact science.

[sobi11]

Originally Posted by hooverphonique

That's because that mod is bad!!! It instructs you to use the RD pad as READY/RDY, which it isn't (it's actually READ DATA, i.e. the actual data read by the drive). Instructions for other drives suggest doing the same, but as you experienced, it messes up with multiple drives and can also kill other drives on the chain since they will have their RDY and RD outputs shorted together..

To use a drive which doesn't have RDY readily available (see what I did there!?), you need some sort of delay circuit to generate it..

So, if there any solution how to do this in proper way? Some picture or diagram? I have many FDD rev 121F and 121G which I wanted to modify.

best regards
Tomek

[Mathesar]

The diskdrive in an old A500 I picked turned out to be unrepairable.
At my workplace I found an old Matsushita / Panasonic JU-257-413P drive that looked a lot like the original one (A JU-253-043P).
As it was not used for anything useful any more I could take it home.

The JU-257-413P is of course a PC HD floppy drive but as it turns out you can modify it for Amiga use.

This what you have to do:

- Set the three switches to 0, MO and RY. (the latter switch puts the _ready signal on pin 34)
- Solder a wire bridge over two pads on the bottom side of the drive. See attached picture. This is actually a jumper that puts the _diskchange signal on pin 2.

And voila, you have a fully functional Amiga drive. Of course, as it is a HD drive, it will only work with DD disks. It will not work with HD disks. To solve this just put some tape on the disks HD hole.

PS, when you are at it, replace the 2 SMD electrolytics on the drive as well. I think leaking caps killed my original drive, see http://eab.abime.net/showthread.php?t=71999

[demolition]

Originally Posted by Mathesar

Of course, as it is a HD drive, it will only work with DD disks. It will not work with HD disks. To solve this just put some tape on the disks HD hole.

Or you could just set the HD/DD switch in the drive permanently so it always detects the disk as DD.

[Jope]

Originally Posted by demolition

Or you could just set the HD/DD switch in the drive permanently so it always detects the disk as DD.

YMMV. Some drives stop detecting diskchanges if you bridge the HD switch. Worth keeping in mind. :-)

[Mathesar]

Originally Posted by demolition

Or you could just set the HD/DD switch in the drive permanently so it always detects the disk as DD.

That is of course also a possibility. Unfortunately, in this drive it is difficult to access the switch. Otherwise a blob of solder would have fixed it

[demolition]

Originally Posted by Jope

YMMV. Some drives stop detecting diskchanges if you bridge the HD switch. Worth keeping in mind. :-)

True, wasn't aware that some drives used the same switch for disk change detection, so only do it if there are two switches next to each other.

[Jope]

Originally Posted by demolition

True, wasn't aware that some drives used the same switch for disk change detection, so only do it if there are two switches next to each other.

Surprisingly, it's not always even about that. I had some drive which had separate DC and HD switches, which stopped doing DC after I shorted the HD switch.

Too bad I have forgotten the make/model since. :-/

[Mrz]

Originally Posted by Jope

Surprisingly, it's not always even about that. I had some drive which had separate DC and HD switches, which stopped doing DC after I shorted the HD switch.

Too bad I have forgotten the make/model since. :-/

that's very rare, in most of the drives you can shortcut the HD switch and nothing happens
The drives you said are not very suitable to work as Amiga drives unless you use always DD floppies because if you insert a HD disk will not push the HD switch then the drive will not work fine in amiga normal mode

[paulo_becas]

Originally Posted by Mrz

that's very rare, in most of the drives you can shortcut the HD switch and nothing happens
The drives you said are not very suitable to work as Amiga drives unless you use always DD floppies because if you insert a HD disk will not push the HD switch then the drive will not work fine in amiga normal mode

You can always use tape to cover the holes

[Mrz]

Originally Posted by paulo_becas

You can always use tape to cover the holes

right, but that's not a very clean solution ( at least for me)

[darefail]

Hi, i don't know if i have to make a new thread or to describe my problem here.
I modified a sony mpf920 that works perfectly in my A500 as internal.
i recently bought an external case (without the drive) and i thought that it works with pc drives. After some attempts i realized that it works with my A500 sony drive that i modified. i checked it in A600.
The problem is that is not recognized from X-copy. Whatever i'm trying to do i get the message "no disk in df1:"
Any ideas? Thank you

[idrougge]

Did it work with X-copy when used as an internal drive?

[darefail]

Originally Posted by idrougge

Did it work with X-copy when used as an internal drive?

Yes as internal in A500 i had no problem at all

[th4t1guy]

I dug out an old Samsung SFD-321B drive and tried the mod today. Whenever the drive is connected, the light is always on. It spins when a floppy is inserted, but I doesn't sound like it's accessing, and no disk is ever recognized.

After some googling, I've found my drive is rev.T6, which according to this post:
https://forum.kryoflux.com/viewtopic...tart=110#p2615

is the revision when these drives lost the density switch, and don't support the Amiga disk mod. I'm not going to revert the changes I did to this drive, so I guess it's going in the trash. Seems like bad luck!

[fordav1]

Since there is no solution in this thread, just an FYI update on the Samsung SFD-321B REV.TA, the drive works just fine in an Amiga with the *correct* modification. The part missed from the previous modification posts is the drive is set to HD mode by default and there's no HD sensor so the drive can't switch modes by itself, but the drive can be hard-set to DD mode. Just remove the solder blob labeled "J0", which is next to J16 in the upper right corner of the board and it works fine, both reading and formatting/writing :-)

[idrougge]

That's good to know, thank you.

[xArtx]

Hello, Why is density select pin on HD floppy drives an input?
It seems the drive can know what disk is in it from the hole.

[asapreta]

Originally Posted by Vot

Hi guys despite previous posts it looks like you can get the 257A607P working (Well Rev F atleast).

If someone can post a good pic of this models pcb I will annonate it with how to mod the drive. unfortunately I had to do a bit of investigative work to get this going and cut a pcb trace in the wrong place.. ended up having to solder directly onto the QFP to access the pin. Trust me you don't want to have to do that at home. If you just cut the traces differently its fine.. no harder to mod than any other panny.

I havn't tested it with sanity artae yet because ive misplaced my floppy but it should be fine.. boots other games ok... just have to check the rdy signal with the demo. I will check it tomorrow and update the post.

Tested with sanity Artae. Works like a dream...

I have done this mod to a Panasonic JU-257A907P (rev F) which the board is the same and the drive doesn't even spin or have any activity.

Did any of you guys have this drive?

Thanks.