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Yet another simasimac SE/30 giving me grief
Posted by: mattsoft on 2026-05-24 16:34:44
Started working on an SE/30 that won't start-up normally. Here are the symptoms:
  • Simasimac-looking image on boot
  • Death chimes immediately at power on
  • Interrupt button does nothing
  • Reset button will re-play the death chimes but not reset the image
I've done the following:
  • Voltages tested at molex on logic board are good
  • Recapped the SMD caps and cleaned the board
  • No battery damage
  • Tested RAM in another machine good
  • Reseated and cleaned the video ROM and PALs
  • Without ROM SIMM, no death chimes but same image -- guessing the ROM SIMM is OK
  • CPU is not halted (F12), CPU clock (E1) is good, CPU /AS and /DS are active -- I think the CPU is good which is probably consistent with death chimes at startup
  • Did the continuity test matrix from the last 2 pages of the schematics (that was labor intensive) and found no bad traces
  • Tested the clock signals from the troubleshooting guide (pg. 38), all are good
  • Performed the ROM address-walk from the troubleshooting guide (pg. 46), and other than the guide being slightly incorrect, the address-walk tested good
My next step is to continue through the troubleshooting guide (pg. 47+) and check the waves from the video ROM and multiplexing ICs.

Any other obvious ideas to check? I don't want to just start pulling chips, so any suggestions I can test with a multi or oscilloscope would be welcome. Thanks!
Posted by: GreenBar0n on 2026-05-24 19:33:31
I have seen the simasimac pattern for the NEC, Ti, and Mt VRAM chips, yours doesn't look like the typical simasima pattern.

It's good that you get a chime of any type, as it means you can most likely use a serial cable to read your error code:

A lot of times a full simasimac condition SE/30 won't load the ROM, like yours seems to be doing.

Seems like testing the Video ROM chip is a good place to start.

EDIT: The Simasimac Repair Guide recommends to test continuity between the PDS slot and ROM slot, and not the CPU directly, because it's easier to access, but if you have a broken trace in between the CPU and ROM, that won't always show up by checking only the PDS slot. I learned that one the hard way.
Posted by: mattsoft on 2026-05-24 19:55:47
Ya, I'm going to check out the video ROM on the scope tomorrow. To connect the SE/30 to a modern PC/Mac via USB, I'll need to figure out all the cables and adapters to make it work. Does someone have handy-dandy links to those? 🙂
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