Welcome, many of our new recruits sign up just to ask questions, too many sign up just to sell stuff in the Trading Post and don't bother to get involved in the community . . .

First off, if you're using the DayStar TurboCache and its "two slot" adapter, those are both 120 pin PDS slots, not the shorter 96 pin NuBus slots.

Just because the TuroCache/adapter combo has room for a second card in its passthru slot does not mean that a power hungry second PDS card would be fine.

Depending on the current draw of the NIC, you might very well be taxing the IIsi's weakly PSU, but the electron pushers will have to answer those questions . . .

. . . along with the freakish occurrence of blown apart board components and burned SCSI cables.

Have you tested with a second MoBo and a different PSU? My IIsi is running great with a Quadra 700 PSU sticking out the top of its lidless PSU Enclosure. If you have one of those or a IIci or IIx PSU available, they probably all supply enough power to rule that out as a cause.

Just from the sounds of it, I'm thinking bad Caps, a flaky PSU and wild power surges, but that's just a WAG, not an educated guess.

Good luck!