Mitsumi D359M3 PC 1.44MB floppy drive mod

[britlord]

Guys. I'm doing this mod, so I can use the floppy drive in my 500 tower project. However, do I still have to cut the track from pin 12, as this guy just soldered pin 10 to pin 12 without cutting the track and soldering a wire from pin 10 to the track that goes to the IC. Which one is correct please..

https://www.youtube.com/watch?v=wApg0gjhIKo

 

[BLTCON0]

Guys. I'm doing this mod, so I can use the floppy drive in my 500 tower project. However, do I still have to cut the track from pin 12, as this guy just soldered pin 10 to pin 12 without cutting the track and soldering a wire from pin 10 to the track that goes to the IC. Which one is correct please..

https://www.youtube.com/watch?v=wApg0gjhIKo

Bridging pin 10 (SEL0) to pin 12 (SEL1) means that df0: and df1: more or less become the same thing. This is obviously wrong.

BUT if you only plan to use a single drive df0: and not an additional floppy drive as df1:, it will work (apparently) correctly.

The modded drive will not return any identification bitstream (neither does the original Amiga DD drive for that matter).
When the system tries to identify df0: (by means of SEL0) it will receive no bitstream and will assume a DD drive is in place (which happens to be correct).
When the system tries to identify df1: (by means of SEL1) the drive will of course be selected again since SEL0 and SEL1 are shorted, but since the drive does not return any ID the system will assume that no drive exists there and won't give any df1: ??? icon in Workbench.

(with 1.x ROMs the procedure is a bit different, but the result is the same: a single df0: drive works correctly)

Of course there's still the theoretical chance some crazy code randomly selects SEL1 for no reason - with pin10 and pin12 bridged, the drive will be selected. The chances of this happening are rather slim, but still if you can perform the proper mod go for it.

 

[britlord]

Guys. I'm doing this mod, so I can use the floppy drive in my 500 tower project. However, do I still have to cut the track from pin 12, as this guy just soldered pin 10 to pin 12 without cutting the track and soldering a wire from pin 10 to the track that goes to the IC. Which one is correct please..

https://www.youtube.com/watch?v=wApg0gjhIKo

Bridging pin 10 (SEL0) to pin 12 (SEL1) means that df0: and df1: more or less become the same thing. This is obviously wrong.



BUT if you only plan to use a single drive df0: and not an additional floppy drive as df1:, it will work (apparently) correctly.

The modded drive will not return any identification bitstream (neither does the original Amiga DD drive for that matter).
When the system tries to identify df0: (by means of SEL0) it will receive no bitstream and will assume a DD drive is in place (which happens to be correct).
When the system tries to identify df1: (by means of SEL1) the drive will of course be selected again since SEL0 and SEL1 are shorted, but since the drive does not return any ID the system will assume that no drive exists there and won't give any df1: ??? icon in Workbench.

(with 1.x ROMs the procedure is a bit different, but the result is the same: a single df0: drive works correctly)

Of course there's still the theoretical chance some crazy code randomly selects SEL1 for no reason - with pin10 and pin12 bridged, the drive will be selected. The chances of this happening are rather slim, but still if you can perform the proper mod go for it.

Ok I'll do the proper mod.You see so far I have cut the track at pin 34, and solder a wire from DEN 3 to pin 43 (is that correct). Joined the DEN2 together...

 

[BLTCON0]

I've only used a Mitsumi drive unmodded on the Amiga, so I can't tell you about any DENx spots. They may even differ slightly between drive revisions, I don't know.

If DEN3 carries the READY signal, then it is correct. You can verify this with a multimeter: Set it to the 20V scale, black lead to ground and red lead to DEN3, with no disk in drive this should continuously read around +5 volts. Insert a disk. When the disk clamps into place it should still be +5 volts but about 0.2 to 0.5 seconds later, when the disk is rotating at full speed that is, it should drop to around 0 volts. Motor stops rotating, it goes back to +5V etc. If so, that's the READY line.