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I tried the logic board on another CC chassis and it worked. Guess the other CC is not 640/Mystic modded. BTW while studying the SIMM area, I could not find any nearby vias or traces that are connected to SIMM header; I wonder if LC575 logic-board is multi layer. If anyone has info about...

Thanks. I was also thinking of getting some sharp probes to make budge work easier. I tried connecting bootable zip drive and it starts booting but got hit by "bus error". I guess I have to check all other CAS RAS pins, not sure if no on-board ram can cause "bus error". The journey continues...

Jagmn thanks for pointing me to the right direction. After checking SIMM pins, I found out DCAS(3) line to MEMCjr was broken. After budging SIMM pin to the resistor pack and turning LC575; walla LC575 showed the flashing disk. Remaining issue, even with SIMM budge-wire, I can't see continuity...

Just an update. I checked most of DFAC-II pins including all ones that go to Cuda and PrimeTime all showing continuity. The ROM chips are not easy to desolder and if they are bad there is no easy way to replace them. So I am thinking of trying to replace Cuda/Egret chip. To any Egret experts...

Hello everyone, I have a LC575 logic board that plays startup chime but shows black screen and immediately plays crash chime. I have washed the board twice, there is no visible trace damages. I also desoldered MEMCjr and cleaned underneath it and soldered it back. Re-flowed all other chips...

Thanks a lot for notes; saved a lot of time for me even having the actual schematics. I looked at all CLUT-MEMCjr connection and also CPU pins; they were all ok. For VRAM pins I just slid probe down the RAM slot until I hear a beep, I don't think that side of CLUT is causing the issue anyway...

Thanks jajan; I looked up on Google and there was no hit for schematic, do you suggest any website/repo/paid service for schematics?

Hi Jagmn, I am glad you fixed your board. I have a LC575 that also chimes but immediately crashes with no image. I removed the on board ram chips cleaned under memory controller, reflew all chips but no luck. I was wondering if you have any schematic or notes for connection s between MEMCjr and...