Fun, Fancy, Frustrating, Floppy Drives - A4000D - Amiga 4000D

[Castellen]

What's the floppy drive type in your A4000, one of the standard Chinon models?  They need a straight wired 34-way cable, i.e. no twists.  Which should be what you have already.

Have you tried another 34-way cable?  Intermittent IDC crimp connectors is a fairly common problem that can develop while removing the cable, and that can cause any number of problems with the floppy drive.

I'm not sure how much DiagROM would help you at this point, though Amiga Test Kit is a good idea.  You don't need a working floppy drive to run it.  Providing you can get the executable onto the hard drive, you can run it directly from there in order to further test the floppy drive interface.  It works very well; you'll need a fairly good understanding of how the floppy drive interface works in order to test it and interpret what you're seeing.  Fortunately it's not complicated.

I'd suggest finding exactly which input/output isn't working before ordering expensive parts and blindly replacing things, you don't want to potentially introduce new problems into the mix.  Besides, you might find it's just a $1 tri-state buffer that's damaged.

[Castellen]

Sounds as though there's more going on than possible floppy drive issues.

At this point I'd suggest testing the following simple as possible configuration:
- v40.68 (OS3.1) ROMs fitted
- A3640 CPU board fitted (both main board clock source jumpers need to be set to EXT)
- Both floppy drive and hard drive disconnected from the main board
- No expansion cards fitted

As above with nothing else connected to the main board except the power supply and the monitor, when you power on the machine, you should eventually get the purple 'insert disk' screen after about 30-40 seconds (of staring at the black screen).  At power on, the power LED should change brightness once.  If you see it flashing as you described, then you probably won't see the 'insert disk' screen, and there's some other hardware problem preventing it from booting.

At this point if you have boot problems, remove all 4 fast memory SIMMs (the 4 nearest the outside of the board), leaving only the innermost chip memory SIMM present.  Repeat the same tests above and see if it boots or not.  If so, you might have a bad fast memory SIMM.

Also try a known good chip memory SIMM if you have a spare (specifically needs to be 2MB, double sided).  As the memory tests in ROM aren't thorough, it can try to boot (and fail) under certain failed memory conditions.

Else there's probably some kind of hardware issue with the main board.  At this point DiagROM would help to see more of what's going on.  The latest version of DiagROM (v1.3) includes good chip memory tests.  If that doesn't narrow it down, then you could send it to me for repair.  I have a run-time hardware debugger that shows the detail of what's happening internally to see where the ROM software is failing, in order to narrow down what area of the hardware is causing issues.

[Castellen]

The offer to repair is very generous. If it comes to that, I'll send a D.M. and we can work out the details.

It's not that generous.  Amiga repairs have been one of my normal jobs for the last 25 years.

Anyway, I'll report the findings here when I'm done. Early tries (with the sketchy ROM socket) give a black screen with no drives connected. But with the CF "hard drive" it boots and it seems to report the correct FAST memory amount and the extended memory on the ZZ9000 (at least with SysInfo). Noting these were quick and dirty preliminary tests and I will be more careful and thorough after the new ROM sockets.

I'm not familiar with the ZZ9000 or if it might affect the floppy drive operation or not.  You wouldn't expect so, but I can't say for sure.

I'd agree with replacing the damaged ROM socket as that can cause future problems.  IC sockets are troublesome at the best of times, more so when they're physically damaged.  Though if the system shows normal signs of life, you should be able to continue with some basic checks on the floppy drive interface.  I'd suggest starting with the latest version of Amiga Test Kit, which you can run directly from the hard drive in order to do the floppy drive tests.  Some people apparently have trouble running ATK from the hard drive, though it's always worked fine for me.  If there are problems running it, I'd suggest trying without startup sequence.