One-pass "flippy" disk support is here!

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Darkstar
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Joined: Thu Nov 04, 2010 7:58 pm

Re: One-pass "flippy" disk support is here!

Post by Darkstar » Wed Oct 12, 2011 7:12 pm

TeaRex wrote:Darkstar, just FYI I did the mechanical part of the modification on my drive with nothing more than a file and a caliper (So you don't have to look it up: eine Feile und eine Schieblehre). Takes a bit longer but it worked just as well.
How did you push in the metal ring for the rail? Screwdriver? That's what I was thinking of using.

Well, maybe I'll just try... If I break it I'll just get another one from eBay or somewhere...

TeaRex
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Re: One-pass "flippy" disk support is here!

Post by TeaRex » Wed Oct 12, 2011 8:08 pm

I didn't push it in at all, there wasn't any room for that - I simply filed it off together with the surrounding plastic.

If you have another drive than the one in the video you can't slavishly follow the steps described there anyway - just let the head go to track 0 and mark its position, then power down the drive, push the head all the way to the physical stop by hand, and you can measure how much material you'll have to remove. You need a total clearance of 2.117 mm below track 0 which is more than it sounds like ;-)

Then you can just turn the drive around and look where exactly the head is hitting against the chassis, that's where you'll have to file off some stuff. On my drive I had to file stuff off both from the drive chassis and from the head assembly, in about four places, and I also had to move the stepper motor itself which of course totally dealigns the drive. And in the end, when the head went as far as it needed to in an empty drive, I still had to push down some kind of metal sleeve around the lower magnetic head because it hit against the floppy disk's own sleeve. Just be careful and stay away from the upper head as much as you can. And if you have to remove any locked screws, it might make sense to lock them again with a bit of lacquer (or with a good amount of ink from an Edding pen).

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Malvineous
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Re: One-pass "flippy" disk support is here!

Post by Malvineous » Tue Oct 18, 2011 1:38 pm

I'm curious about trying this, but I grew up in the PC era and have never been exposed to any other platforms. If I wanted to get some cheap flippy disks off eBay for testing, what would I be looking for?

AmiDog
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Joined: Sun Oct 31, 2010 8:16 pm

Re: One-pass "flippy" disk support is here!

Post by AmiDog » Tue Oct 18, 2011 3:22 pm

Would be great if someone with the knowledge and tools to perform the modifications could buy a couple of those NOS 5.25" drives, like this, which can be found at eBay, performed the modification and offered them for sale. I understand a modified drive might cost about 100 EUR in labour alone, but I'm sure there's a demand for drives even at that price.

dusty1000
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Joined: Wed Sep 28, 2011 10:34 pm

Re: One-pass "flippy" disk support is here!

Post by dusty1000 » Fri Oct 28, 2011 12:37 am

OK, finally I did it! I gave up trying to modify this old GDR TEAC Clone drive as it used a stepper with no ability to go below track -1.
So I got two different drives from ebay, one EPSON SD-680L and one of the known working Panasonic Type. The Epson Drive cannot be modified, as the connection between the stepper and the head has no room left to go below track zero. But the Panasonic drive is really easy to modify. I just used a side cutter to remove the disturbing parts from the chassis. To push the metal ring, I used a sharp knife to cut off some of the plastic around it and pulled out the ring with a calliper. After removing the ring its really easy to cut of the rest of the plastic. Now you can push back the ring just with a thumb.
The bypass circuit is really simple I replaced the 2n222 transistor with a 2n3904 and it works like charm.
First the bypass doesn't seem to work, but I just forgot to cut off the connection to pin 33 even on the second attached 3.5" Drive.

RJMcInty
Posts: 81
Joined: Fri Nov 26, 2010 12:26 am

Re: One-pass "flippy" disk support is here!

Post by RJMcInty » Sat Oct 29, 2011 4:29 am

dusty1000 wrote:OK, finally I did it! I gave up trying to modify this old GDR TEAC Clone drive as it used a stepper with no ability to go below track -1.
So I got two different drives from ebay, one EPSON SD-680L and one of the known working Panasonic Type. The Epson Drive cannot be modified, as the connection between the stepper and the head has no room left to go below track zero. But the Panasonic drive is really easy to modify. I just used a side cutter to remove the disturbing parts from the chassis. To push the metal ring, I used a sharp knife to cut off some of the plastic around it and pulled out the ring with a calliper. After removing the ring its really easy to cut of the rest of the plastic. Now you can push back the ring just with a thumb.
The bypass circuit is really simple I replaced the 2n222 transistor with a 2n3904 and it works like charm.
First the bypass doesn't seem to work, but I just forgot to cut off the connection to pin 33 even on the second attached 3.5" Drive.
Hey! Good job! Glad that you were able to modify the drive successfully! You're right about the second drive; I only use a single drive setup, and didn't think about that setup...

dusty1000
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Re: One-pass "flippy" disk support is here!

Post by dusty1000 » Sat Oct 29, 2011 2:12 pm

I also did some investigation about realigning the Panasonic drive, which seems to be very easy too. If you connect the logicboard without adding the head, the stepper starts spinning. This shows that the firmware tries to find the zero position of the head. To proof this, I activated the light sensor with a screwdriver. The stepper stops instantly. OK, so I tried to adjust the alignment by just sliding the track zero sensor. This really works!. To realign the drive I started reading a known good c64 disk with dtc and disconnected the plug to the stepper from the logicboard, before dtc finished reading track 0. Dtc continued to read, but the stepper won't move... so every following track shoud be track zero. Now you can turn the stepper forward and backward slowly until dtc catches a good track zero. Now you can release the screw of the track zero sensor and slide it slowly while testing between TP8 and TP10 with a multimeter.
Maybe there is a way to constantly read just one track with dtc, but I can't find a way to do this. This would make the alignment even more easy.

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mr.vince
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Re: One-pass "flippy" disk support is here!

Post by mr.vince » Sat Oct 29, 2011 2:24 pm

dtc -s4 -i6 -c1

where -s sets the track you want to check.

:)

dusty1000
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Re: One-pass "flippy" disk support is here!

Post by dusty1000 » Sat Oct 29, 2011 4:37 pm

Ok, I think the Panasonic drive has a very high potential for further hacking. At the moment I'm thinking about auto-aligning to an inserted disk. This would make it possible to even read disks written by a misaligned drive. This is the idea:
I'm gonna adujust the track zero sensor to track -8 which is just for physical protection.
With a simple PIC-Controller containing an 8 Bit AD-Converter I'm gonna programm the following:
1.) At power on, step back to track -8 ( thats simply what the drive firmware does )
2.) Then slowly step foward until head 0 gets a high signal ( assuming that there is no track before track zero )
This can be done by just catching the analogue signal from the head and giving some step signal to the stepper.
3.) After the real track zero is found, just disable the physical track zero sensor and take over its function by counting the track signals send by the logicboard.
4.) Step the drive to somewhere above track zero an reset the drive firmware.

Rakki
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Re: One-pass "flippy" disk support is here!

Post by Rakki » Mon Nov 28, 2011 6:46 pm

dusty1000 wrote:First the bypass doesn't seem to work, but I just forgot to cut off the connection to pin 33 even on the second attached 3.5" Drive.
Interesting. I did exactly same for my dual drive configuration but by some reason it doesn't work in dual drive mode (Kryoflux configured + ribbon cable connected to both drives) or in single drive mode when both drives are connected with the ribbon cable. Pin 33 is removed from Sony MPF920 3.5" drive. Currently 5.25" Panasonic JU-475-5 1.2 MB is running on single drive mode because going to track -8 fails always with dual drive config.

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