Floppy Replacement

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The floppy disk drive in older amigas are starting to wear out.Those which do not, or at once stage, did not have a hard drive, are particularly effected. The amiga floppy drive is fairly rare and expensive, although, Graham Chui at Comp Karori still has stock as I write this (6/3/01).

For those that can't get a real amiga floppy, you can use a PC floppy drive. Now before you get excited, you can use a High Density drive, you won't be able to read or write High Density disks with it. Anthony Hoffman has done the conversion and has the following to say:

It is worth pointing out that quite a number of late model PC drives will not work correctly with the Amiga no matter what you do, trust me, I've spent many an hour trying! They might work with a Catweasel controller, but that's hardly the Amiga's motherboard floppy controller. The Teac drive I had gave heaps of problems, it came close to bouncing off the wall several times :)

Other older drives like Sony and Chinon will often work by simply swapping the diskchange and ready line (pins 2 and 34) in the ribbon cable.

However, these modifications to the Panasonic JU257 means it will plug into any Amiga as a direct replacement for the unit 0 (DF0:) floppy drive. The drives are also cheap and reliable. You can get them as low as $20 wholesale but might be hard to find in places as they are a few years old now. Most PC wholesalers like to buy in the cheapest, cruddiest drives they can lay their hands on.

Anyway, here are the instructions:

This is going to sound complicated, but it is in fact very easy.

OK, you'll need:

I think you have to take a cover off the bottom of the drive, it's been a while since I did this now.... There is probably two or four small screws holding the bottom cover on, I forget....

Once you have the thing open, look at the PCB. Not far back from the 34 way connector you'll find 3 pads with the lables RY and DC beside the outer two. If you look VERY carefully, you'll see that the centre pad is linked to the DC side pad. Using the knife, cut the PCB track running from that centre pad to the DC pad. 2 or 3 firm slices usually does the trick. Be careful, you don't want to damage any other track......it's very easy to slip with that knife!.

Ok, now that is cut get the knife again and VERY carefully scratch that green coating stuff off the surface of the RY, DC and centre pad between them. You want to get 3 nice copper coloured pads. You can't solder to that green stuff you see. Don't worry if there's a bit of green crap still there, just get the bulk of it off..

Once that's done get your soldering iron and link the centre pad to the RY pad. You might be able to "blob" solder between them, but it might be better to use a 4mm long bit of wire or something. A pair of tweezers might help here..

Be careful not to heat the copper PCB pads too much as they'll start lifting from the board..

Now get the hookup wire. It has to join the DC pad to pin 2 on that 34 way connector. Hopefully you can figure out which one this is by yourself. Pin 1 is nearest the outside edge of the drive and connects to ground, as do all the other odd numbered pins. Pin 2 is the one beside it......hopefully you can work it out as it's not that easy to explain..

One other link to make. Somewhere else on the drive's PCB (I forget where, probably somewhere very close to the 34 way pins) is 3 similar pads, but they'll be labled something like DS0 and DS1, or maybe Drive 0 and Drive 1? I forget, but you'll see it..

You'll notice the DS1 pad is linked to the centre pad. Cut this link with the knife..

Like you did before scratch the green stuff off the pads. This time you only need to do the centre one and the DS0 pad. Once they're nice and coppery looking just link DS0 to the centre pad..

Then you just have to plug the drive into the Amiga and it should work! Make sure the 34 way cable is wired "straight" and doesn't have a twist in wires 10 to 16 (like PC drive cables are)..

You'll need some fine soldering skills, so if you aren't used to soldering, give these instrustions to a friend who does. I'm more than willing to offer any other help..

That information was from memory, but I don't think I left anything out. I know it was pretty simple. Please let me know if you need any more help or info..

A bit vague I know but it should be enough to get things going..

Oh, and if you get really stuck finding someone to do the modifications, then find a working JU257 and send it to me with a prepaied courier bag for returning it. I'll modify and test it for free. Only takes a couple of minutes.

Have fun,
Anthony.

And Anthony adds:

I was just looking through some old notes I made on these drives and thought it important to point out a few things when disassembling the JU257:.

The PCB is actually upside-down, you have to unscrew and lift it up to work on it. The stepper motor which drives the heads along is plugged into the underside of the board, meaning you have to unplug it *BEFORE* lifting the board..

If you don't (like /someone/ might have neglected to do once) then you end up ripping the flexible loom off the stepper motor along with half the pins moulded into the motor. You then end up making a dodgy looking new loom out of telephone wire which isn't very fun :(.

The idea is to gently lift the rear of the PCB and using some very fine sharp nose pliers, grasp the flexible loom and pull it out of that socket..

And yes, you obviously have to plug it back in once you're finished :P.

I think the same thing applied for the heads as well, but they're easy to get undone once the stepper motor cable was off. There was two head connectors (two heads, top and bottom), side by side. You might want to mark one flexible loom with vivid marker so that you don't get em mixed up when plugging back in..

Or the head connectors might have been permanently soldered on rather than plugged in??? If so be extra careful not to rip them off..

I think that's the only real trap to watch for..

Apologies for the jumbled information. I've worked on so many drives I've forgotten the peculiars of each one..

Just be careful when working on them and you'll be fine..

Anthony.

copyright 2001 Tom Parker - last modified 26 Mar 2001