Converting a Sony MPF920 floppy drive

[amiga_BOY]

Looking at my old Sony floppy drive model MPF920 it looks like it can be converted for Amiga according this link http://jope.fi/drives/. After modding can I just connect it directly as a replacement for the internal floppy drive?

[torsti76]

Originally Posted by amiga_BOY

Looking at my old Sony floppy drive model MPF920 it looks like it can be converted for Amiga according this link http://jope.fi/drives/. After modding can I just connect it directly as a replacement for the internal floppy drive?

Yes, that's the idea.

[amiga_BOY]

oh thanks! I thought you still need some circuitry to convert it. That's good then as i have several spare floppy drives around.

[torsti76]

Originally Posted by amiga_BOY

oh thanks! I thought you still need some circuitry to convert it. That's good then as i have several spare floppy drives around.

You'd only need circuitry to use the drive in HD mode. For DD disks, moving the /DISKCHANGE signal from pin 34 to 2 and moving the internal jumper from DS1 to DS0 is enough.

Note that these drives don't have a proper /READY signal. Thus, some games may refuse to work.

[solarmon]

Please note that a modded PC drive will technically work, but the eject button may not line up properly or at all.

[amiga_BOY]

So I tried the mod with the Sony floppy drive i mentioned. It seems to work sometimes but most of the time it's having a hard time reading/booting my diskettes. I can hear it trying hard to read disks. My Amiga keeps popping "read/write" error. These diskettes work just fine with the original internal floppy drive.

Any ideas what could be?

[torsti76]

Originally Posted by amiga_BOY

So I tried the mod with the Sony floppy drive i mentioned. It seems to work sometimes but most of the time it's having a hard time reading/booting my diskettes. I can hear it trying hard to read disks. My Amiga keeps popping "read/write" error. These diskettes work just fine with the original internal floppy drive.

Any ideas what could be?

Often it helps to clean the spindle and put some fresh grease on it. Also, if you are using HD disks it's important to put some scotch tape over the HD indicator hole.
To avoid this, you could also solder a wire accross the pins of the HD detection switch.

If all that doesn't help your drive is misaligned. But try these simple things first.

[solarmon]

Originally Posted by amiga_BOY

So I tried the mod with the Sony floppy drive i mentioned. It seems to work sometimes but most of the time it's having a hard time reading/booting my diskettes. I can hear it trying hard to read disks. My Amiga keeps popping "read/write" error. These diskettes work just fine with the original internal floppy drive.

Any ideas what could be?

Sounds like may the disk presence switch not working? Or some issue with the ready signal?

In any case, use Amiga Test Kit to check the floppy drive signals and see whether they are as expected.

[amiga_BOY]

When I done the mod I didn’t really transfer the DSO resistor to the DS1 but just soldered a jumper wire which basically shorted them. So i fix it by following what’s really in the instruction and that is swap the ds0 and ds1 by moving the resistor. It’s all working now!

[amiga_BOY]

Originally Posted by solarmon

Please note that a modded PC drive will technically work, but the eject button may not line up properly or at all.

Yeah that's my main issue with PC floppy drive. Will i able to use a modded PC Floppy drive for external use and connect it direcly from the DB23 port? This setup seems to work well on a Gotek drive

[Jope]

Originally Posted by amiga_BOY

Yeah that's my main issue with PC floppy drive. Will i able to use a modded PC Floppy drive for external use and connect it direcly from the DB23 port? This setup seems to work well on a Gotek drive

You will need the drive id / motor latch circuit.

[amiga_BOY]

Originally Posted by Jope

You will need the drive id / motor latch circuit.

Is the circuit just for PC floppy drives or it's needed even with an original Amiga internal drive?

[torsti76]

Originally Posted by amiga_BOY

Is the circuit just for PC floppy drives or it's needed even with an original Amiga internal drive?

Usually, it is needed with original drives as well. For DF1+, a well-behaved READY signal is mandatory. That's what the latch circuit provides.

If your drive issues a correct READY signal, it's sufficient to set the DS1 jumper to have ONE external drive. For more drives, you need the daisy-chain id switching which is usually coupled with the latch circuit anyway.

On the big boxes, there's a jumper DF1: on/off. If set to on, this activates the DF1 latch circuit which, for the big boxes, is part of the mainboard.

[Jope]

Originally Posted by torsti76

Usually, it is needed with original drives as well. For DF1+, a well-behaved READY signal is mandatory. That's what the latch circuit provides.

No, the latch (usually a 7474 flip flop) is there so that the motor can be controlled for each mechanism separately. There is only one internal and one external motor signal shared with each drive. When the external drive's select and motor are on at the same time, the latch remembers this and leaves the motor running until the drive is selected without the motor signal on the next time.

If your drive issues a correct READY signal, it's sufficient to set the DS1 jumper to have ONE external drive. For more drives, you need the daisy-chain id switching which is usually coupled with the latch circuit anyway.

No, the READY signal generated by the drive mechanism is for after the motor has been started and is up to speed.

The external drive case's circuitry provides a ready pulse for drive type/presence identification. This shares the same pin (READY) on the bus, but it is used for a different thing. The pulse is usually provided by a 7438 NAND chip and there is a specific algorithm for pulsing SELECT and MOTOR to read the ID pulse [1].

On the big boxes, there's a jumper DF1: on/off. If set to on, this activates the DF1 latch circuit which, for the big boxes, is part of the mainboard.

Looking at the A2000 schematics [2], the jumper connects the ready pulse from the 7438 NAND chip to the floppy bus, the 7474 motor latch for the internal df1 is always connected to the internal drive motor signal at the floppy bus, but this doesn't hurt anything.

[1]http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node01AB.html
[2]https://www.amigawiki.org/dnl/schematics/A2000_R6.pdf page 11

[lesta_smsc]

I remember ruining a perfectly functioning (brand new) PC drive back in the day trying to mod it. I'm sure I followed the guide exactly but the picture that was given was actually of the wrong drive so it all went horribly wrong!

There are some drives that are much simpler to mod (changes to jumpers) and so in future I will probably end up getting one of these lol. In fact, I have bought one just for this purpose but the mod is simpler on this drive on the motherboard ... not to mention I refurbished a rusty Amiga A500 floppy drive that I thought was going to the tip and ended up working perfectly fine with the rust removed!

[torsti76]

Originally Posted by Jope

The external drive case's circuitry provides a ready pulse for drive type/presence identification. This shares the same pin (READY) on the bus, but it is used for a different thing. The pulse is usually provided by a 7438 NAND chip and there is a specific algorithm for pulsing SELECT and MOTOR to read the ID pulse [1].

That's the theory. But none of the external cases I have do this the right way, I.e. the drive's own READY is never passed through.

Looking at the A2000 schematics [2], the jumper connects the ready pulse from the 7438 NAND chip to the floppy bus, the 7474 motor latch for the internal df1 is always connected to the internal drive motor signal at the floppy bus, but this doesn't hurt anything.

It does for HD drives, but I agree that this is of no immediate concern here.

[Jope]

Originally Posted by torsti76

It does for HD drives, but I agree that this is of no immediate concern here.

A HD drive is the special kid here. You must leave the DF1 jumper off if you have a HD mechanism as DF1, as in this case the drive mech provides the ID stream.

[amiga_BOY]

Just finished my Amiga Drive Selector which should also work Gotek and floppy drives like the Sony MPF920.

[Methanoid]

Originally Posted by solarmon

Please note that a modded PC drive will technically work, but the eject button may not line up properly or at all.

Thats what I was here looking for now... Is there such a thing as list of ones that can be modded AND can either line up OR have the button stolen from original drives?

[EDIT] http://jope.fi/drives/ lists drives but NOT which would be casework friendly

I have a Teac FD-235F which doesnt like me and am wondering if the button would transfer to a modded Teac FD-235HG for example?

[Jope]

Hardly any old drives have an eject button that can be swapped directly into a newer drive. Thankfully new buttons can be 3d printed for many popular mechanisms.