IIci with no SCSI

[Performa430]

I've got a IIci that I've recapped and cleaned. For some reason, it will not boot from SCSI - internal or external. I've tried known good HDs and BlueSCSIs. Nothing. It will boot fine from floppy.

I've checked all of the traces from the SCSI chip with good continuity from each pin. I've also checked each pin of the SCSI connector with good continuity from each pin. What's next, replace the SCSI chip itself? Are those even available?

 

[RetroTheory]

It's possible the scsi chip is blown but I would look also around UD11 (VIA) , as there are 3 caps there that can leak and do damage there, and some control signals for scsi pass through that IC.

 

[ScutBoy]

Also, IIci can be funky with termination power, at least on the internal connector. If you are doing the external device only, I think you need at least a passive terminator on the internal connector.

 

[Performa430]

Also, IIci can be funky with termination power, at least on the internal connector. If you are doing the external device only, I think you need at least a passive terminator on the internal connector.

Right. I remember from seeing a Branchus Creations video that I needed to have a SCSI drive plugged in to the internal connector, which I did have at all times.

It's possible the scsi chip is blown but I would look also around UD11 (VIA) , as there are 3 caps there that can leak and do damage there, and some control signals for scsi pass through that IC.

There were four pins that connected directly to UD11 - all showed good continuity. There are 8 data pins that are shared with UD11 - all of those showed good continuity.

There were two pins that I didn't test from the SCSI chip because I don't know where they go. Does anyone have an idea where these connect? I'm not familiar with the abbreviations.

 

[mdeverhart]

Those will probably be connected back to the CPU or the Memory Decode Unit, but I’m not sure which. SEL is the chip select so that the SCSI chip knows the CPU is trying to talk to it, and DACK (Data ACK) signals back to the CPU that the CPU read/write to the SCSI chip is complete.

 

[Performa430]

Well, interestingly enough, it is working just fine now. I think I might know what was happening...maybe. I put in a ROM-inator II to see if it would boot and it did with no problem. Restarted with external BlueSCSI (and ROM-inator II), booted with no problem. Hmmm. I then pulled the ROM-inator II and started with external BlueSCSI - good. With internal BlueSCSI - good. Works fine now.

In trying to determine what changed, the only thing I can think of is I used a different jumper on W1. Perhaps the old jumper wasn't making connection?

 

[trag]

Could also be an oxidized/dirty SCSI connector and unplugging/plugging things cleaned it off enough to start working. We've seen a few folks here have SCSI problems caused just by the connector being old and using something like de-oxit fixed it up.