Yet another simasimac SE/30 giving me grief

[mattsoft]

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!