Help with external floppy

[caver99]

Hi all,

I am after some help if possible.

I have an Amiga 1200 that when i got it was missing mouse port and internal floppy drive.
I have an alps pc modded to work as df0: and is running perfectly.
I have just bought from ebay a Cumana cax 354 external floppy, but when plugged into the 1200 everything boots as normal but when i insert a known good floppy disk into df1: i get df1:Unreadable, so i thought dirty heads,
cleaned them but still the same, i removed the drive and inserted it as df0: everything worked as normal.
I have checked that the cable has continuity and that i get to the 1200 main board.
With the top off of the drive the disc spins and the head is trying to read track 0 or what ever it reads first.
i have got the schematics and only 4 connections don't go to the internal drive, they are _sel3, _mtrx, _sel2 and _reset wither one of these is not going to the external port or possibly one of the ls chips on the drive board is down, but i don't have any other amiga to test it on or another drive to test on the 1200.
is there anyone near Ellesmere port that might have one we can test the drive on?

[prowler]

Hi Caver99,

I live nowhere near Ellesmere Port, as you can see.

However, if no-one local to you can help, you are welcome to send it to me and I will check it, repair it if necessary and return it to you for just the cost of postage.

[caver99]

Thanks, i may end up taking you up on that.
but first i was thinking of trying to replace the ls chips on the little pcb as there the only things i can see might be causing the read problem.
as looking at this http://www.ianstedman.co.uk/Amiga/am...rive_port.html gives what the pins do and i am more than certain thats its the read or ready line of the drive itself.
But i maybe totally off the ball here of cause.

[prowler]

Originally Posted by caver99

Thanks, i may end up taking you up on that.

I'll be glad to help you if it comes to that.

I like the Cumana drives. They do have a fairly high current requirement (~900mA), which is always worth bearing in mind, but I have found them to be very reliable, and the Citizen drive mechanisms they use are designed for easy access if you have to clean the heads.

Originally Posted by caver99

but first i was thinking of trying to replace the ls chips on the little pcb as there the only things i can see might be causing the read problem

I expect you're spot on. There's not really a lot that can be causing the fault if you've checked the drive mechanism out, so it's probably worth giving that a try if you feel confident enough.

[caver99]

thanks, yeh the drive mech works spot on when connected to internal connector.
i have looked around and will get the 2 chips and 2 sockets seeing as the drive cost me £2 plus £3 p&p from ebay i thinks its worth giving it a go.

[Cymru]

If it has a switch on the back for "1 & 0" then check the switch to make sure it is working. Zero = off and One = on.

[caver99]

you mean the enable and disable switch, yes that is working as when in disable nothing will work, when in enable the drive behaves like its a blank disc.
on the other hand if you mean on the drive itself, i have tried on the various setting and put back to default afterwords still the same reactions from drive

[Cymru]

I mean the switch is cheap and fails leaving the drive is disable mode all the time c

[caver99]

oh ok, i have tested the switch and on continuity it switches ok and when plugged into the 1200 when in the en position the drive tries to do something but when in the dis position it wont do anything.
i hav tried also to to do permanent enable by bridging the switch and same as when in the enable position.

[Cymru]

Then it sounds like a multimeter set to continuity will sort out all but the chip issues; a second similar drive might help by exchanging components.

[caver99]

thats now where it falls flat on its face as i would like to have another drive but i dont, only this one for a while.