I have a decent SE/30 logic board, slightly affected by battery acid.
After adding a couple of bodge wires, it works almost perfectly.
I replaced the original RTC with a new ATTiny RTC module.
I installed 4 × 4 MB SIMMs in Bank 0 (16 MB total). The machine boots in 32-bit mode using a BMOW custom ROM, passes memory tests, and works correctly. That would be fine, except that when I try to add another 4 × 4 MB SIMMs (known-good modules) to Bank 1, I get the chime of death.
Checks performed
All four SIMMs in Bank 1 have +5 V and GND.
There is continuity on the RAAF address lines from Bank 1 to resistor packs RP4, RP5, and RP6, and from there down to the UI/UJ 74F258 multiplexers.
There is also continuity from the multiplexers to the ROM SIMM.
The multiplexers are unlikely to be faulty, otherwise Bank 0 would also be affected.
There is continuity on the CAS lines from Bank 1 to the resistor pack RP1 and to the UD1 74F240 buffer.
Question
I am following this path step by step, but it is turning into a long journey.
Is there a way to identify a more likely culprit?
Is there a way to be more focused on the troubleshooting?
At the bottom, there is this scratched pad near C61, I dunno where the via is supposed to go, and the schematics with the "REPEAT-2" is not helping me
After adding a couple of bodge wires, it works almost perfectly.
I replaced the original RTC with a new ATTiny RTC module.
I installed 4 × 4 MB SIMMs in Bank 0 (16 MB total). The machine boots in 32-bit mode using a BMOW custom ROM, passes memory tests, and works correctly. That would be fine, except that when I try to add another 4 × 4 MB SIMMs (known-good modules) to Bank 1, I get the chime of death.
Checks performed
All four SIMMs in Bank 1 have +5 V and GND.
There is continuity on the RAAF address lines from Bank 1 to resistor packs RP4, RP5, and RP6, and from there down to the UI/UJ 74F258 multiplexers.
There is also continuity from the multiplexers to the ROM SIMM.
The multiplexers are unlikely to be faulty, otherwise Bank 0 would also be affected.
There is continuity on the CAS lines from Bank 1 to the resistor pack RP1 and to the UD1 74F240 buffer.
Question
I am following this path step by step, but it is turning into a long journey.
Is there a way to identify a more likely culprit?
Is there a way to be more focused on the troubleshooting?
At the bottom, there is this scratched pad near C61, I dunno where the via is supposed to go, and the schematics with the "REPEAT-2" is not helping me
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