How to modify a Sony MPF 920 to provide a ready signal

[endangermice]

I recently grabbed a 3.5" drive from my lovely box of random bits and bobs in order to use with the CPC. Like many 3.5" drives, this one does not provide a ready signal to Pin 34 by default so we have to create one. You can connect a drive to the CPC without this by connecting Pin 34 (the ready signal) to Pin 33, but this makes the CPC think the drive is ready all of the time which works beautifully until you type CAT without a disc inserted. The computer will appear to hang (in fact it will respond if you place a disc in the drive) and soft resetting the machine doesn't help - the FDC is stuck. The only solution is a hard reset.


To make the Sony MPF 920 3.5" drive behave in exactly the same way as Amstrad's 3" drive we need to perform a few modifications starting by opening up the bottom of the drive (3 screws) which will allow you to remove the metal panel and reveal the main PCB. When you open the drive the main PCB should look something like this:




1. Cut the trace from pin 34:




2. Hook Pin 34 to the +5v of the floppy detection switch circled here:




You should end up with something that looks a little like this (excuse my terrible glue gun skills):




When you're done,  put everything back together (don't forget to remove the connection between pin 33 and pin 34 on the ribbon cable or the drive will return a read fail when no disc is inserted) voila, a CPC that no longer hangs when there is no floppy disc inserted and better still, provides you with the somewhat more useful disc missing message:




Job done

[Bryce]

Nice explanation, and photos that are in focus! A rarity among disc conversion guides

Bryce.

[endangermice]

Thanks Bryce, I took a load of pictures trying to ensure that they were in reasonable focus - not so easy using an IPhone and trying to balance everything as you take the shot . Hopefully this guide will be useful to someone!

[Gryzor]

Oh this is great, hope it will be of service to someone, somewhere!


A few points:
-Why the MPF920? Any special reason for it or it just happened to be lying around?
-Would be better to insert the pictures as "expandable". They are great though!
-A more general note, aren't such guides more suitable for the wiki instead of the forum? Just asking... can I copy it to the wiki?

[Bryce]

We already have this (half finished) page here: Modify PC floppy drives - CPCWiki - The Ultimate Amstrad CPC Community &
This info should definitely be added to it.

Bryce.

Edit: Some further information on the MPF 920: JC30 and JC31 select whether the disc acts as DS0 or DS1. If you are using this drive internally, you should remove the JC31 bridge and solder it onto the JC30 pads.

[endangermice]

The 920 was indeed a drive I had lying around. Since all drives are different! The guide is specific to that one but hopefully has enough background info to allow others to figure out how to modify different models (I figured out the Sony it was pretty straightforward).


The images are hosted on my web space and linked from there. I tried uploading them to the forum but I always get an error saying they have failed security. I'm not sure whether I can make linked ones expandable?


You can of course copy it to the wiki. I would have added it there but I don't have permission. I presume only the select few can add wiki pages...?


Thanks for the positive feedback, I appreciate it .


Cheers,


Damien

[Gryzor]

Hm, let's try uploading one of your pictures:
[attach=2]


[EDIT] Huh, it worked. Can you try doing it again and telling me the exact message you got?


As for the wiki, of course not!!! It's open to everyone and anyone, but you need to create an account! Why did you get the idea that it's closed?

[endangermice]

I'll try again when I get back to the UK (in Paris right now). The first few pictures I uploaded worked fine but then it stopped working. I did do a search for the problem and it looks like a random bug that can sometimes occur though no one has been able to find out why yet!


I figured the wiki might only be opened to certain users so as to ensure that a quality is met. I tried logging in with my forum credentials but that didn't work - I guess I need to register separately.


I'll have a look when I get back home and would be delighted to make it a wiki article.

[Gryzor]

Yup, there was an issue with MIME checking and whatnot, and the devs had said, in essence, "cannot be solved, rewriting, wait for a next version". I relaxed security controls, and I have not seen it since, but let's check it out. Sometimes just opening the offending file in a program and saving it again worked...

[endangermice]

I'll have a look. Makes sense, I write code for a living so I know how easy it is to let some bugs slip in - none of us are perfect and sometimes the problem isn't as easy to solve as people think!

[Gryzor]

Not a problem, let's check it out when you get back (have a great time, btw!) and we'll see. Tomorrow I'll create an article in the wiki, just remember to let me know what problems you encountered with writing one -if any.

[Bryce]

I've had pictures in the past that refused to upload as jpg, but if you converted them to png they worked fine. I just assumed it was a bug and I convert everything to png now.

Bryce.

[protek]

Nice hack!  I've also got a Sony MPF but I'm hoping to convert it to a high density Amiga drive. A Samsung SDF-321 that has a jumper changed from DC to RDY will do for my Amstrad needs.

According to a thread in English Amiga Board, another way to provide the RDY in Sony MPF is to route a wire from IC21 to pin 34 and of course to cut the trace on the PCB.
http://eab.abime.net/showthread.php?t=43265

[El chocobollo]

Hi! please allow me to relaunch this topic, as I'm trying to modify this exact type of disk drive, the Sony MPF 920 (it's the one I've got available) in order to use it internally in a driveless CPC I just got.


The problem is, I can't see the pictures attached in the first post by Endangermice. And, as I'm a mere user with no knowledges of electronics at all, I'm completely lost without the "do it like that step by step, little fellow".


I also tried to find the topic at the wiki, since it's mentioned in this thread that the info would be added there, but I couldn't find it.


Are these pictures available anywhere? Could you please tell me what should I modify in my Sony MPF 920 drive to use it as an internal drive in a CPC?


Thank you very much!!!!!

[Bryce]

Take a look at the picture here: Sony MPF920-E E/131 modified to work with the Amiga

Bryce.

[Munchausen]

So if I understand this, for CPC drive mods all you need to do is find the disk detect switch, and as long as it changes from 5V to GND when a disk is inserted, you can just wire the output of the switch to pin 34?


This is great, as it means you can mod drives without needing data sheets for the controller ICs on the drive!


I didn't know it was this simple...

[Bryce]

Some drives are even simpler. They have a jumper for DS:0 / DS:1 and another jumper to determine whether the signal is "Disk Change" or "Disk Ready".

Bryce.

[TFM]

And some older drives are even more simple, you just plug them in an they work without any modifications. I just think it would be a good idea to have a list of them on the CPC Wiki.


I remember couple of them, but have to check asap.

[El chocobollo]

Great, thank you very much! I understand that I should make the same modifications to make it work with the CPC, right? Thanks again!!!

[Guy0me]

Hello everybody i'm looking something about adding a Sony MPF920(2001) or MPF920-E(2008) in a 6128+ and i found this post but the screen capture are gone  .
Is it possible to have those pictures ? Some of you are saying about put the article on the wiki but i found nothing about it !
Thank you guys !

[Morri]

Hello everybody i'm looking something about adding a Sony MPF920(2001) or MPF920-E(2008) in a 6128+ and i found this post but the screen capture are gone  .
Is it possible to have those pictures ? Some of you are saying about put the article on the wiki but i found nothing about it !
Thank you guys !

Me too! Just received a sony mpf920 today and would love to see those pics if they're available.

[Bryce]

If one of you can take a decent hi-res picture of the PCB, I'll do a new description-picture for you.

Bryce.

[Guy0me]

If one of you can take a decent hi-res picture of the PCB, I'll do a new description-picture for you.

Bryce.

[Guy0me]

If one of you can take a decent hi-res picture of the PCB, I'll do a new description-picture for you.

Bryce.

[Bryce]

That was quick! Ok, here's the quick answer:

Getting a Ready signal:
Step 1 - Cut the track going to the headers pin 34 (marked with x in bottom left corner)
Step 2 - Connect pin 18 of IC2 to pin 34 of the header (shown as red line)

Making the Drive A: (If you want to use the drive as B: then this step isn't required)
Remove the bridge (black component with "0" on top) from JC31 and use it or a short piece of wire to short the JC30 contacts.

The other drive you posted seems to be exactly the same, just the layout orientation has been turned 90°, so this will work on both versions.

Bryce.

Edit: Just realised that the blurred first picture uses a different IC, can you possibly take a better picture of that drive or let me know the part number of IC2.