OK I've gone full-circle. I managed to get everything installed and running with my stock SE/30 ROM and Mode32 on System 7.5.3. But I have exactly the same problems as when I started: Weird artefacts appearing on the screen and frequent crashes.
The good news, I guess, is that I can cancel out the Mac ROM as the cause of the issue. I have exactly the same problems with a IIsi ROM and a SE/30 ROM (@joethezombie I did need to patch the system file to use the IIsi ROM, and I needed to do a clean install to revert back to my SE/30 ROM)
I can also cancel out the ROM on the Daystar Turbo - as I have exactly the same problems with the original ROM and the 4.1.1 ROM.
I also know that both the Ethernet card and the Daystar Turbo work perfectly by themselves, so there's no hardware or software issues here.
So I think the issue can only be one of the following:
The power supply on the Mac is not up to the task of powering both cards. I tried a stupid test where I turned the brightness right down on the screen in the hope that I might see a different result - but no change.
My Twinspark Card is faulty - i.e. there is something wrong with the top PDS port, or some other issue with the card
I'm thinking of ordering another Twinspark card - which is expensive I know. If it fixes the problem then I should be able to get my money back on the first card, and if it doesn't fix the problem then I can offload my extra Twinspark card to one of you good folk.
Guess I am old since I don't collect CRT TVs but I do have a couple in the house from the 90's (purchased new and still use for old school console gaming). I like the look of an old Atari 2600, Colecovison, 5200, Dreamcast, original Playstation on a CRT TV.
Both models are Panasonics, only one of which works. I kept the broken one because it was an $800 27" TV and I was going to fix it but never got around to it (multiple svhs and compisite inputs front and back). The other 27" TV has just composite inputs front and back and a more curved screen.
I do have a sony trinitron broadcast CRT and those make great gaming monitors.
Howdy! Indeed it appears someone has replaced some caps and couldn't be bothered to find axial replacements!
Troubleshooting could consist of trying a known-good speaker of a similar type and/or testing the original speaker with another audio source.
And of course checking the associated wiring/connections.