A2000 floppy problem

[gdanko]

I have a REV 6.2 A2000 WITH 3.1   ROMs. When I boot it up I get the "please give me a disk" animation, but when I insert a disk the unit reports a disk error... This is no matter which boot floppy I use. I have tried a number of boot disks and they all fail. I've tried every combination of floppy drive and cable I could imagine (3 different cables and 6 or so different floppies) and the result is always the same.

Now then, I took one of the offending floppy drive/cable combinations and was able to successfully boot a rev 4.3 2000 as well as a rev B 4000. So all signs point to the 6.2 board.

There is very little battery corrosion on the board, so I re-seated every chip on the board and tried again. Same story. The error is along the lines of "DF0 is a non-DOS disk".

I am at a loss here. Maybe the chip that controls the floppy disk is acting up? But I do not know which chip that is. I guess I could look it up somewhere.

Have you ever heard of such a thing? An error occurs on every attempt to boot off DF0.

By the way, I put the 3.1 ROM from the 6.2 board into the 4.3 board and everything worked like a charm.

I am usually not daunted by Amiga problems but this one has me stuck!

[Chain]

Looks like fried CIA, you can try to swap it from 4.3 working board.

CIA chips are marketed 8520.

[gdanko]

Will a rev 4.3 CIA work in a 6.2 board?

[Lockon_15]

Try to swap & test the whole pair of CIAs. Last year, I fried one CIA and had the chip replaced. Machine booted, but after few mouse clicks it frozed. I tried disconnecting various peripheralls, but nothing worked out. Problem was solved when I looked more carefully into both chip designations. It seems that there are 2 major types of CIA working at different clocks (1 & 2Mhz). When I set a same type pair nodes problem was gone.

[gdanko]

Okay I'll swap both tomorrow. I hope the 4.3 CIAs will work in a 6.2!

[spirantho]

Correct me if I'm wrong, but can't you switch your even CIA with your odd one? Then something else will go wrong but your floppy will work so at least you'll know then it's definitely a CIA that's knackered.... no doubts about compatibility of CIA then either.

[gdanko]

Aha so it WAS the CIAs. Lucky I have access to another set so I can replace the ones I borrowed from the other machine.

[Amiga4k]

It was only 1 of the CIA chips. Namely U300 CIA chip. So if you re-test the chips at U300 only, you'll have a spare. The bad CIA should cause "floppy problems".

[Amiduffer]

Boy, not only does the CIA overthrow governments and spy on everybody, they even cause floppy disks to malfunction!  :crazy: