HD Floppy drive in A1200

[jbenam]

Will try to test again ASAP, sadly I had my Amiga 1200 back in storage before I could read this. If I don't reply to this thread this weekend, feel free to PM me as a reminder

[pipper]

I managed to fix the FZ-357A and it now reports the correct drive ID again.

So the mystery remains, why would a FB-357A not work in an A1200, while the FZ-357A does.

I think I will give up on this mystery as the FB probably would not fit anyways and the FZ works again.

Attached is a picture of the captured start of the drive ID sequence on the oscilloscope.

[cpiac64]

please, explain me how to you have fixed it

[Bruce Abbott]

Yes, please tell us how you fixed it.

BTW I have built an interface to produce the HD drive ID, and hope to test it tomorrow.

[pipper]

The fix was nothing special. The drive itself still worked for DD floppies, but would not produce the proper 1010… sequence for the drive ID when inserting HD floppies. There are four chips on the FZ-357 board. The main controller chip, a driver for the stepper motor and three logic chips whose sole purpose is to produce the drive ID sequence when a HD floppy is inserted.
In my case, I had accidentally put the floppy power the wrong way around (the A1200 side connector is not keyed). So I assumed that this must have fried one of the three logic chips. I got replacement for all three, but it was the 7W04F chip (a three way inverter) that was the culprit. I took it off with some hot air and soldered the replacement into its spot. Et voila!

If the main controller chip would have been nuked, there’s probably no way to get a replacement part :-(

The same drive had failed before; the weird connector to the track 0 sensor was shorting out against the case. It actually fried a trace on the controller board and I had to replace that with some wire.

Originally I had another issue with the drive: when inserting HD floppies, it would detect it and produce the right drive ID, but it would never slow down to 150rpm. In this case the Floppy cable was the culprit. The above mentioned circuit to produce the drive ID also has its fingers in the 150rpm switch. The drive expects pin 1 on the connector to be connected to GND (which it normally is via the floppy cable) to send the “slow down” signal to the controller when a HD floppy is inserted. So in my case the cable was broken in just the right way to disconnect pin1 (which is normally not a problem, all odd numbered pins on the connector are just GND), rendering the slow down circuit not functioning.
Why it is using Pin1 in this way is a mystery.

[Mad-Matt]

Not entirely relevant to the topic but I thought id ask anyhow.

Has anybody had any success with HD Floppies with the Panasonic drive included with Escom A1200 using this aminet driver https://aminet.net/package/disk/misc/HiDensity

I tried it years ago after modifying a cable to make the Panasonic drive work in my commodore 1200. For me, it would appear to work fine writing and reading back files to a HD disk. But after a disk swap it was likely the disk would never be readable again so it wasn't all that useful

[jbenam]

Apparently my FB-357 doesn't detect HD floppies at all in the A1200. I haven't been able to test it with the test program, but I can't seem to format HD floppies as 1760Kb, only 880Kb.

[Bruce Abbott]

Originally Posted by pipper

There are four chips on the FZ-357 board. The main controller chip, a driver for the stepper motor and three logic chips whose sole purpose is to produce the drive ID sequence when a HD floppy is inserted... I got replacement for all three

It would be interesting to see the circuit those chips are in. Do you know if the schematic is available, or if not can you trace it and/or post a photo of the drive PCB?

Unfortunately I had a small setback. My spare A500 motherboard is now dead. I don't think anything I did caused it, but until I know for sure I won't be doing any more disk drive tests (especially not on my spare A1200 motherboard or running machines!).

[pipper]

There you go. This is what I was able to reconstruct from buzzing out the drive_id circuit some time ago. Imagine my surprise when I found out about the completely needless Pin1 business in there.

Disclaimer: no warranties on correctness and completeness.

[cpiac64]

my hd 357a i suppose have 7w04f dead, i have changed and tested all chip except the 04

without the 3 chips (7w04f, 74ls12,74ls74) work like 880k

[cpiac64]

drive hd and dd difference

[Boboo_SK]

Look here, my old projekt
http://eab.abime.net/showthread.php?t=82991

[Bruce Abbott]

Originally Posted by Bruce Abbott

Unfortunately I had a small setback. My spare A500 motherboard is now dead.

Good news! The fault turned out to be the 28.37516MHz oscillator module, which had low output amplitude. So it was just a coincidence, nothing to do with the disk drive.

Now I just need to source the correct replacement. I have a 30MHz module in there now, which works but the frequency is 6% too high which might cause trouble. This could be the most mildly accelerated A500 ever!