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Old 12 November 2012, 19:22   #1
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Help - my 500 is killing floppies

Hi guys, after a very long time, I've got my original A500 back having had 3 owners since I originally bought it.

It's got a Roßßmuller A2MB/500 memory expansion on which the RTC battery leaked though not at all badly and I've replaced it with a new NiMH battery.
I also recently picked up a couple of external floppy drives (each has a Citizen mech) with a few games but unfortunately no full WB 1.3 disks. I gave the machine a decent clean out and got the fluff out the floppy drive and carefully cleaned the heads.

Wanting to create some game disks I've made a null modem cable etc. and I got a WB 1.3 disk set from a supplier on eBay. The disks arrived and I booted up to a Workbench 1.3.3 desktop. First thought was to create a backup of the WB boot disk so I popped a floppy into DF1: and chose the Initialise option - it failed pretty much straight away. I put in a new HD floppy in with the HD hole covered but it also failed. I tried a few different disks in both DF1: DF2: and even DF0: each unable to get past verifying track 0 luck and have been unable to write a backup WB disk.
Then murphy's law struck and the act of ejecting the WB disk it has somehow become corrupted (I presume the boot sector) the WB disk so it is no longer recognised. AAaargh. It was write protected too so not sure WTF happened.

I don't have an XCopy disk or any tools to repair it and I find it hard to believe I've got 3 drives that can read but not write!!

Can anyone help me out either with a Transwarp / Hombre / Workbench 1.3 boot disk or suchlike? Happy to pay postage etc.

Old 12 November 2012, 20:12   #2
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Are you getting any squeaking or squealing noises from the drive while reading these disks?

What sometimes happens is old disks develop a layer of mould on the surface, and when you use them initially they seem fine, but the mould gets scraped up and accumulates on the drive heads which massively increasing the friction. At that point, the drive will start scoring visible grooves into the surface of healthy disks.

A floppy cleaning kit (felt disk with isopropanol) should sort out the drive, but it's going to be a recurring problem with old disks if they've been stored anywhere remotely damp. Maybe someone knows a way of restoring the disks?
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Old 12 November 2012, 20:38   #3
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It can be the disks. They bit-rot.
HD disks are specially unreliable.

All your problems sound like bad disks which don't necessarily have been destroyed by the A500, it was more probably a problem of age and storage conditions. What robinson says is something to consider too, if you hear "whistling"not only your disk is crappy (probably has mould on it), but it's also fucking up your disk drive.

I's funny how most people blame the hardware for stuff like this, thinking floppy disks are eternal or something. They are the most frail piece of stuff you will have on an old computer and usually have to be your main suspect for data loss or strange behaviour on loading/saving.
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Old 12 November 2012, 20:59   #4
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Many thanks for the responses.
The drive sounds pretty good though a couple of disks did make a bit of a rubbing noise in any of the drives. I disposed of those disks. No sqeals from the drive (just a few in my head when the WB disk ceased to boot!!!)

I have run a cleaning floppy on the drives
Old 19 November 2012, 21:25   #5
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I've now had a chance to do some more testing. Curiously when you insert a write enabled disk into either internal or external drive it displays DF0:NDOS or DF0:BAD (or DF1:NDOS or DF1:BAD) on the desktop. Ejecting the disk and write protecting the disk will render it readable again.
If you try writing data to the disk when it is write enabled it corrupts the disk.
Also Workbench and Xcopy III are unable to format any disks at all. as it cannot verify the data written to disk.

I have removed cleaned and refitted all socketed chips though I notice only Paula and Gary play a part in floppy data and logic.

A google search did find reference to at least one A1200, A2000 and A3000 showing similar symptoms.

So at the moment I'm stuck with a read only machine that I cannot write a disk with - any one resolved this issue before ?
Old 19 November 2012, 22:53   #6
roy bates
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thats interesting,have a look in the front of the drive on the left hand side,there should be two prongs sticking up these are the actuators for two switches.

get a can of switch cleaner and spray a bit into the swithces,then with a flat blade screwdriver push them down a few times then apply a bit more.clean up the mess if any and try a floppy.
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Old 20 November 2012, 00:54   #7
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hi Roy, thanks for taking the time to reply. I'm pretty sure it's not the write protect switch as I've tried 4 different floppy mechs with the same result, so I'm assuming the issue is on the motherboard.

I've been looking in the amiga hardware tech docs and the CIA A seems to handle the registers for the write protect switch so I'll do some tracing with a meter and try swapping the CIA's around.
Old 20 November 2012, 19:21   #8
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Woohoo, I've managed to fix it!!
Spent a while with the schematic in the back of the A500 manual and used a multimeter to make sure all pins were connected. I discovered that the track from U36 74LS38 pin13 did not make it back to Gary Pin 44 - this is labelled as _DKWEB
I soldered a link from pin13 back to a pad connecting to Gary pin44 and lo and behold I can now write floppies again.

Sods law really as I'd just pulled the trigger on a spare A500 board from Airey36. Never mind, I'm happy lol.
Old 20 November 2012, 20:35   #9
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Originally Posted by FlatLyna View Post
I soldered a link from pin13 back to a pad connecting to Gary pin44 and lo and behold I can now write floppies again.
Good work. Well done!
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