No SCSI on Macintosh LC

[Mirokai]

Hello folks,

I just got me a very cheap Macintosh LC from the bay. Battery didn't explode fortunately and capacitors only leaked slightly.

Has got a very nice Accelerator Card with 68030 and 68882 FPU in the PDS slot.

I cleaned everything thorougly with water, soap and isopropyl alcohol after removing the capacitors. Also recapped the logic board and power supply and it works nicely until I try to boot from a SCSI drive. Lido says "Arbitration failed" and Snooper 2.0 tells me that the SCSI addresses are empty. Tried SCSI2SD which works fine on two Macintosh SE and also a working Quantum drive with 170 MB.

I checked the voltages rails and they are perfectly fine after recapping. Stable 5V, -5V and 12V (+- 0.1V) even when connecting two floppy drives and external SCSI.

Did anyone have a similar problem and knows how to solve this?

 

[LaPorta]

Always possible someone removed a SCSI drive without turning off the power back when, ruining the SCSI chip. Someone with far more expertise than me would know how to scope signals from the chip.

 

[bibilit]

So the LC works fine with the Quantum drive but not with the SCSI2SD ?

 

[Franklinstein]

I think he means the Quantum drive is known good but doesn't function in the LC's internal SCSI spot.

Does external SCSI work? If so, you'll want to look around the SCSI chip and the internal connector for any damaged traces or bent pins or anything. There are also some passive devices between the chip and the connector that may have been corroded. See if the internal drive works with and without an external drive connected; sometimes weird termination problems will result in one configuration working and another not.

If no SCSI works, yeah it's probably something bad near the SCSI controller, or the chip itself. 

 

[Mirokai]

Thanks for all the replies. Unfortunately neither the internal SCSI nor the external are working. I tested everything thoroughly with a lot of possible combinations and different drives.

And yes I tested the quantum drive on a different machine and even got the driver for the accelerator off it. Will share them with the community soon since I didn't find them on here.

Found a good looking LC II logic board on the bay and will try my luck with this one. I hope it will fit in the LC case?

 

[Franklinstein]

Bummer about your SCSI subsystem. But at least you can use that LC board for spares in the future.

The LC II board was offered by Apple as a direct upgrade for the LC: it even has the fan/speaker connector pads on the board for easy swapping. You could use the much faster LC III board (which itself was offered as an LC II upgrade) but you'd have to change the fan and speaker to the independent types with their own plugs to use it in your LC. I'm not completely sure if the LC 475 had the same or slightly higher rated power supply, but it will also fit in an LC chassis with the new fan and speaker.