Faulty A1200, floppy disk loading OK, but writing and formatting not work

[amiga2000]

Hello. My A1200 normal, KS 3.0, FZ-354 internal FDD, no expansion card. With the internal floppy disk loading and boot OK, but writing and formatting not work, error messages. Why? The disks are not write protected. Disk name change, filecopy (write), format impossible. Xcopy formatting with verify not works, verify error on all tracks.
I tried on already with an other FDD (FB-354), nothing. This drive 100% OK with A500+.

[Toni Wilen]

Does formatting erase old data (format without verify in xcopy) or is old data still fully readable?

[Daedalus]

What do the error messages say? Do they say the disk is write protected, or something else? Did you try the floppy ribbon cable in the A500 too? Sounds like a problem with either the write protect, write data or data write enable signal, which could be caused by a bad cable. Motherboard / CIA faults are also possible, but the cable is easy to check by swapping it.

[DanyPPC]

I have the same problem with a Rev 1.D4, my technician has identified the problem in the Audio PAULA chip.

[bebek]

You can have some tracks damaged due to caps leak. Drop me pm if you would like to repair it but have nobody local.

[amiga2000]

A1200 motherboard version 1D4, fully recapped. Workbench 3.1 boot OK from floppy disk. IDE-CF, RGB out, audio out, turbocard slot, joy+mouse handle OK. CTRL+Amiga+Amiga reset OK. Games from floppy disk and from CF card (Whdload) OK.
WB 3.1 boot from CF card, and:

1-- Format floppy disk, fastformat, "Inicializing disk" message 15-20 s, and "Not a valid DOS disk." Disk name "DF0:NDOS".
2-- Format floppy disk, normal format, 0-79 track 0-99%, then "Couldn't format cylinder 79". Disk name "DF0:NDOS". All old files available. I tried 5+ disks.
3-- Floppy flat cable OK. Disks not write protected.
4-- Xcopy format with verify, track 0, 1, 2, etc. all, diskside 0 and 1 verify error, red "8".
5-- Xcopy erase disk (verify option not available), track 0-79 green "0". All old files available.
6-- Tsgui adf file to disk write not OK, with verify option "Error No. 1 (verify failed)" on all tracks, all old files available. Without verify 0-79 track OK, but all old files available.

[Daedalus]

So data is not getting written at all it seems, That would make me think the write enable or data write line is damaged somewhere along the way.

[Hewitson]

Originally Posted by DanyPPC

I have the same problem with a Rev 1.D4, my technician has identified the problem in the Audio PAULA chip.

I'm not convinced...

[Toni Wilen]

Originally Posted by Daedalus

So data is not getting written at all it seems, That would make me think the write enable or data write line is damaged somewhere along the way.

It is guaranteed to be write enable related because it will also enable erase head which would destroy all old data even if write data line is dead.

First step is to check that write enable (DKWE in schematics) line is not broken and not shorted to any other line. It is probably possible to check write enable line state even with a volt meter during format without verify.

[amiga2000]

The floppy cable was faulty. I don't understand how it's possible, because I never removed the FDD, or cable from the A1200 machine.

[chocsplease]

Glad you've fixed it.

I have almost the same issue with my towered A1200, only here the writes don't work on the external floppy drive either. I'm suspecting one or both of the CIAs.

Thing is I don't know which is responsible for the writes as the net is saying that the odd is for floppy control, and the even is for 'some' floppy functions.

Anyone any ideas what floppy functions the even cia is used for?

[Daedalus]

Yep, glad it's sorted. Sometimes cabled just go bad, usually where there wasn't a perfect connection at one of the connectors, and years of vibrations finally made it come loose.

Originally Posted by chocsplease

Thing is I don't know which is responsible for the writes as the net is saying that the odd is for floppy control, and the even is for 'some' floppy functions.

Anyone any ideas what floppy functions the even cia is used for?

Thing is, the Write Enable line comes from Paula, but it's run through a logic chip on the way to the ports. There's also an EMI filter on the line (a resistor and a capacitor), so a few things to check there.

For completeness though, the CIA floppy functions are as follows:

Even CIA: Outgoing signals - motor, select 0-3, side select, step and step direction.

Odd CIA: Incoming signals - ready, track 0 sensor, write protect sensor, disk change indicator.

[chocsplease]

Originally Posted by Daedalus

Yep, glad it's sorted. Sometimes cabled just go bad, usually where there wasn't a perfect connection at one of the connectors, and years of vibrations finally made it come loose.


Thing is, the Write Enable line comes from Paula, but it's run through a logic chip on the way to the ports. There's also an EMI filter on the line (a resistor and a capacitor), so a few things to check there.

For completeness though, the CIA floppy functions are as follows:

Even CIA: Outgoing signals - motor, select 0-3, side select, step and step direction.

Odd CIA: Incoming signals - ready, track 0 sensor, write protect sensor, disk change indicator.

Many thanks, select and motor etc are OK so suspect number 1 is that cap, followed by that logic chip and then Paula (I guess?)