SCSI issue w/ Color Classic

[Ralphieboy]

I bought few days ago a very clean Color Classic.

Obviously, caps leaked on the Mother Board.

Our fellow forumer Bibilit is in charge of the restoration.

First of all, he performed a complete recap of the MB.

Then, testing the MB: no gong and no pointer.

After a desoldering/resoldering of the chip that manages the audio:

Gong: ok. Pointer: ok. But, no system boot nor "?" logo.

Bibilit has disconnected the HDD SCSI ribbon, performed a reboot that led to the "?" logo.

I have to mention that the HDD was already out of order.

After desoldering/resoldering the SCSI chip and trying w/o success to boot from an internal or external HDD, Bibilit assumes that the SCSI chip is faulty.

I managed to buy from eBay some SCSI chips (codename AM85C80) and hope this will revive this very clean Color Classic.

Has anybody experienced a similar issue?

 

[Bolle]

On the SE/30 this behaviour is often caused by broken traces between the SCSI chip and the connector for the HDD.

Grab the datasheet of the SCSI controller and the pinout of the edge connector of the logicboard and check if all SCSI signals are present on the edge connector.

 

[bibilit]

To complete the post, i should say that booting without any SCSI ribon (internally or externally) will get me to the flashing mark right away, without any sign of trouble (a good chime a moving pointer)

booting with a SCSI cable , chime and pointer, but soon after chimes of death and sad mac codes.

Connecting a SCSI cable afterwards will freeze the system, the pointer is not moving anymore, and the floppy is not flashing anymore, removing the cable will get me back to a moving and flashing behaviour.

I didn't see any broken trace, the chip is not close to any capacitor, and was clean.

Acting as if the system was expecting something from the SCSI bus, only had a problem once with a CC, when the logic board was not booting from a good hard drive, but not this kind of behaviour.

 

[Bolle]

When you say no SCSI cable you mean you unplug the connector from the hard drive?

You don't necessarily see broken traces (or vias) all the time, that's why I would check continuity between the bus signal pins on the controller and the logicboard edge connector at first.

I suppose you already looked if term power fuse and diodes are ok? Hot plugging can damage those.

 

[bibilit]

When you say no SCSI cable you mean you unplug the connector from the hard drive?

Yes, correct, or from the rear connector (external SCSI HD)

The Logic Board has the same behaviour in my own CC (with a good HD)

Some pictures...

 

[bibilit]

I have made some improvements.

To cut a very long story short, i have removed and replaced the SCSI chip (no dice) removed and re flow some chips in the neighborhood... and just after that, the Logic board stopped throwing sad macs.

The board in my own working CC, worked, but only as far as the blinking floppy.

using its own casing, i hooked a jaz drive in the external port, and i got a happy Mac and a message stating the SSW was not correct (the enabler was not present)

So this morning, i hooked a Hard Drive in the same port and with the floppy disks, managed to set a proper install, worked flawlessly, and the CC booted from a hard drive for the first time.

My hard drive is too bulky to go inside, and SCSI cable too short for a test, so for the time being, probably only the external port is working, or a SCSI voodoo is present in my own CC.
 

 

[bibilit]

I have not seen anything obvious in the white connector (internal SCSI side) but a trace can be damaged.

point is, the Color Classic is working fine, booting right away from the external port, sound is loud and clear.
 

 

[bibilit]

Image on the CC is slightly tilted.

On the early Compacts, is pretty easy to solve the issue, the procedure is the same on the CC or different ?