View Full Version : Reverse floppy cable Damage?
10-29-2006, 05:17 AM
Does anybody know if reversing the floppy cable on an A2000 is known to blow chips?
I have just brought an A2000 mobo back from the dead, and now it seems to have a strange floppy drive problem. It will boot and read from a floppy, but eventually errors at block 892 usually (sometimes 880).
It's not the disks or the drives as I have a working 2000 in which I have swapped parts to test.
It's not the 8520's or the Gary or the Denise.
There are some garden variety 74LS series chips associated with floppy function and I'm wondering if reversing the cable could have caused those to go. Nothing is overheating either.
Stupid floppy cable has the pin numbers moulded into the plastic on the back of the plug, but they are back to front. Their is also no obvious red wire to orient to pin 1, the ribbon cable has numerous stripes on it.
10-29-2006, 08:29 AM
And the floppy cable itself has also been checked?
10-29-2006, 11:54 AM
yes thanks mate, checked the cable as well :-)
10-29-2006, 01:02 PM
Normally, there is on the plugs of a flatcable a little triangle/arrow wich points at pin number 1.
10-29-2006, 06:07 PM
Yep, that's right. Whoever made the cable in my A2000 put the little arrow so it points to pin 33 & 34 instead.
10-30-2006, 09:00 PM
No, you don´t blow anything if put the cable in wrong way.
But the floppy unit of yours is going brain dead soon. Consistently errors in same location in any floppy disk means mechanical problems. Buy (or convert a peecee) new one.
Amigan since 1989
Known drunk since 1982 (don't know quite well - I was drunk)
Now pregnant (hey, not me: my wife is)
- Do'nt mak spellign erors!
10-31-2006, 12:36 AM
There is nothing wrong with the floppy drives. I have tested them on a second working A2000 that I have.
I have also taken the good drives from the working A2000 and they also misbehaved in the A2000 I'm trying to fix.
It is likely that I still have a poor connection somewhere after having replaced the ROM and 68000 sockets. I managed to remove them very cleanly and it appeared that no damage had occured, but after replacing the sockets the machine wouldn't boot, which is what it was doing before i replaced the sockets anyway.
Upon removing the sockets I located a problem that was likely the initial cause of the Boot failure. I repaired that problem and then soldered on the new sockets. I found a similar, but not the same problem, after replacing the sockets.
I eventually located a trace from the ROM to the Agnus that was dodgy and I repaired it and now she boots up, but floppies misbeahving. Still running tests ATM, I have the sneaking suspicion that the CPU is running slower than it should. I don't want this one to beat me, can't stand to see an Amiga go to the grave.
10-31-2006, 05:09 PM
Could be old caps in the mobo. They don't leak, but if not working you could have some misbeheaving. Look the caps near the processor and Agnus.
not the small ones, the electrolitic ones. Change the video ones too (security measure, I have some trouble with them, here).
11-01-2006, 10:03 AM
I had similar problems with a A500 friends.
It was mainly due to oxydation on each IC and theirs respective supports.
Use a good product to clean.
For the drive i may do some miracles do put it in a bin :rtfm:
11-01-2006, 07:25 PM
Thanks to all.
I have done the cleanup thing, as this board has acid damage from the leaking battery problem. Both 2000's I have were given to me for free, and the damage already existed on both of them.
I have also replaced the two sockets that showed any oxidisation problems, ROM & 68000.
I have checked by swapping out all custom chips, power supplys and Floppy drives and the problem exists with floppy drives connected only to the affected board.
When I had the machine in bits and was testing things, I know that I put the floppy drive cable on backwards at the Mobo end. It also could have been on for sometime before I realised, as the drive lights were not facing me and I didn't see the light on DF0: was stuck on.
But hey, as I said earlier the numbers on the plug 33 & 34 have to go to where pin 1 is labled on the board. The plug has been put on back to front I think. There is a pin 1 labeled on the mobo next to the floppy interface, of course I put it on backwards. The other 2000 is exactly the same, it's plug is on backwards, weird.
I'm fairly convinced that something is still not right on the board after the socket replacements. I will have to go do much more tedious testing to try and find what's wrong.
If it's not that, then it must be something to do with the drive cable being put on backwards and some damage to chips/components other than the 68000, Rom or other custom chips.
I have built an OS for the affected 2000 using the good 2000 to set it up. The affected system boots fine from a HDD. But the floppy drives are only accessable at boot time, and will only access for about 30 secs before they start to grind and error. This is just enough time for me to run binddrivers and tell it to continue booting from the HDD.
Cheers and thanks again to all.
11-01-2006, 10:09 PM
What would be really nice is some diagnostic software that can give info about signals that are not functioning correctly.
I have things like sysinfo and have seen similar programs, if I use sysinfo to do a floppy test it crashes the machine.
I know there is a diagnostic ROM floating about which would be nice to get hold of. I believe it's included in Amiga Forever 2006, which will probably be my next buy :-)
11-01-2006, 10:55 PM
Source:From the Amiga Troubleshooter 1993
Floppy read and or write errors: Paula, 68000, Agnus.
In your case, suspect the 68000 socket or chip.
(I have spare 68000's if your interested)
11-01-2006, 11:28 PM
Awesome, that's the stuff I'm after :-)
Ok, in that case I will focus my attention on the 68000 (socket) again.
Thanks for the offer on the 68000's, but I have three to swap in out and of course they are all behaving equally ATM.
Problem is probably round the socket. I just spent some time trying to run a game or two and it takes forever to load from the HDD or to boot up for that matter.
I thought I had swapped all custom chips, but in hindsight I think I didn't do paula, because I couldn't see what paula had to do with it.
I think the machine is running slow, even though benchmarks say it's running at the correct speed of 7.09Mhz roughly. I thought maybe, this in turn might be causing the floppy drive to spin too slowly and therefore causing the errors.
Been a while since I've used anthing but 030's, so I may have forgotten how slow it is :lol:
Back to the grindstone...
I will test some more in a day or two.
:-) :-) :-)
11-03-2006, 02:44 AM
All is good, found another small prob and just watched it boot from a floppy to workbench. Also played a game and so far all looks healthy.
Fired up Xcopy and did a disk to disk copy and tis a sweet thing indeed.
now back to the SCSI GVP Rom problem <sigh>
Thanks to all for your advice.
Another Amiga rises from the ashes :lol:
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