SCSI controller crashes A2000

[techhusky]

I have an A2000 with GVP 68030 Combo board, 2mb chip & SCSI2SD storage card that started acting up a few weeks ago.  In short, when the system boots the HDD light stays mostly lit, slightly flashing.  It takes a very long time, but Workbench does eventually come up and is somewhat usable.  The HDD LED continues to stay lit until the mouse pointer locks up and then the system crashes.

I have tried a heap of stuff, with no luck.

* Replaced the SCSI cable
* Tried a new SD Card
* Cleaned the board connector and slot
* Swapped the socketed chips, one-by-one from a spare, non-working motherboard
* Purchased an A2091 card with ZuluSCSI drive.  (Yes, I went a little overboard!) Disabled the SCSI controller on the GVP board.  Same behavior using the A2091.
* Removed the GVP card entirely.  Same behavior.
* The battery was just starting to corrode.  I pulled it off the board and there is no visible sign of damage. (I have a button battery replacement on order)

The machine boots and runs fine from floppies.  Some things I've read indicate that it could be capacitors or the power supply.  I don't see any leaking or bulged capacitors.

Has anyone seen anything like this?  Any suggestions would be appreciated.

-Jeremy

[Boing-ball]

Sounds like capacitors to me. Don’t assume that no sign of cap failure and everything is okay. When was the last time the capacitors were replaced? I’m assuming these are original to the system? If so a recap would be a good start.
The VARTA battery will cause damage. You did a clean up afterwards?

[Castellen]

The machine boots and runs fine from floppies.  Some things I've read indicate that it could be capacitors or the power supply.

If the system works reliably from floppy disk, but there's apparent SCSI issues, then power supply/capacitors are unlikely.  It's not as if the power supply magically knows if the system is booting from floppy disk or SCSI then somehow decides to deliver unreliable 5VDC or not.

If the hard drive LED is almost continuously on, and it's extremely slow, it may be that you're using using FastFileSystem, the volume has a validation error, and the system is scanning the entire volume as part of the validation/correction process.  If you boot with no startup-sequence, then just leave the system alone until the hard drive LED eventually goes off (might take an hour or more), does it eventually validate?

A SCSI bus termination problem can cause symptoms where SCSI transfers are unreliable, though interesting that the issues persist with a different SCSI controller and SCSI drive - are you using the same media on the different SCSI controller?  Are you able to test the same SCSI hardware and media in a different Amiga?

There's a small chance of a memory issue causing the system instability.  Booting from hard drive does use more memory (file system is in memory, plus disk buffers, etc), meaning it the system would be using other areas of memory that it it wouldn't be when booting from floppy.  An easy check is to use the AmigaTestKit bootable floppy, or https://aminet.net/package/util/moni/MemCheck12

[techhusky]

Thanks for the replies.  The caps are original to the system.  The battery was only slightly corroded.  The corrosion did not reach the board, but I cleaned up the surface just to be safe.  I don't have an oscilloscope, but I tested the output on the power supply under load (loading jpeg's from floppy) with a voltmeter.  +12.03V and +5.04V on the lines so unless there is noise, I think it is OK.

I've tried different media on both SCSI SD card devices.  One SD card has a fresh OS 3.x install.  Unfortunately, I do not have another Amiga to test.  I tried different termination jumpers/switches and that didn't change behavior.

I'll start with bootable test floppies.  Unfortunately, I can't have a SCSI controller up while I test.  Any SCSI access sends it into a tizzy.  If that doesn't turn up any issues, I try recapping since it would be a good idea to replace them anyway.  I've had this machine since 1991, purchased from a family member who bought it new in 1989.  It's been amazingly trouble-free up until now.

[Castellen]

If you've tried completely different SCSI hardware and media (would be very useful to know they work correctly in another machine) and get the same result, that would suggest some kind of hardware issue with the main board.  A possible clue is that many SCSI controllers use DMA (direct memory access) hardware modes to transfer data to/from memory, where booting from floppy won't use that same hardware.  At a guess, there might be some kind of problem with hardware specific to interrupt requests or DMA.

You might get some further clues using DiagROM, which is about all you'll be able to do without any test equipment.

Beyond that, and without another known good machine to test the SCSI hardware, there's probably not much more you can practically do.  You'll likely have to send the main board and one of the SCSI controllers for assessment/repair.  I can help with that if you can't find anyone locally: http://amiga.serveftp.net