I would very carefully examine the area around the 53C80 chip for damage/corrosion from the leaking capacitors. Also, to the extent you can, visually trace the connections to the 53C80 pins back to their origins and then check them with an ohmmeter to confirm that there's actually a good connection there.
In other words check continuity from each 53C80 pin to the pin of whatever other component it connects to. Make sure the circuit board is still doing its job. This will be tedious.
The output side of the 53C80 should be fairly straightforward, as the pins should connect to the appropriate pins on the SCSI connector.
Do you have a datasheet for the 53C80? That has the pinout and will give you a better idea of what each pin should connect to.
Cast an especially critical eye on any circuit board vias which connect traces to the 53C80. On my IIci (back in the 90s!) capacitor leakage pooled in a via and corroded the copper lining such that the traces on front and back of the circuit board were no longer connected. The damage was not really visible until I used magnfication and even then it took a continuity test to confirm.
If there's a schematic of the SE/30 logic board available get that and use it to check the 53C80 connections. Failing that, the block diagram in "The Guide to the Macintosh Family Hardware" would be helpful. Looking at the block diagram for the IIci (developer note available as PDF) it looks like the peripherals sit right on the main data and address busses.
Ah, forgot about this. I have the 53C80 datasheet available here: http://www.io.com/~trag/DataSheet/Z53C80.pdf. The D7-D0 lines probably connect pretty directly to the CPU data bus. The address lines and the other control lines may pass through one of the two VIA chips. The IRQ line almost has to.
Still, doing a comparison of the 68030 pinout and the 53C80 you should be able to line up a good number of the pins to check.
In other words check continuity from each 53C80 pin to the pin of whatever other component it connects to. Make sure the circuit board is still doing its job. This will be tedious.
The output side of the 53C80 should be fairly straightforward, as the pins should connect to the appropriate pins on the SCSI connector.
Do you have a datasheet for the 53C80? That has the pinout and will give you a better idea of what each pin should connect to.
Cast an especially critical eye on any circuit board vias which connect traces to the 53C80. On my IIci (back in the 90s!) capacitor leakage pooled in a via and corroded the copper lining such that the traces on front and back of the circuit board were no longer connected. The damage was not really visible until I used magnfication and even then it took a continuity test to confirm.
If there's a schematic of the SE/30 logic board available get that and use it to check the 53C80 connections. Failing that, the block diagram in "The Guide to the Macintosh Family Hardware" would be helpful. Looking at the block diagram for the IIci (developer note available as PDF) it looks like the peripherals sit right on the main data and address busses.
Ah, forgot about this. I have the 53C80 datasheet available here: http://www.io.com/~trag/DataSheet/Z53C80.pdf. The D7-D0 lines probably connect pretty directly to the CPU data bus. The address lines and the other control lines may pass through one of the two VIA chips. The IRQ line almost has to.
Still, doing a comparison of the 68030 pinout and the 53C80 you should be able to line up a good number of the pins to check.