Mac SE - Gray Screen, no startup sound, no pointer

[TheBurgerKing]

I have two Mac SE computers, motherboard 820-0176-B / 620-4125 for both. One works fine, boots up to the disk with the question mark and has a pointer. The pointer moves with the mouse. The other board boots to the gray screen, makes no sound and does not have a pointer and the disk never appears. Nothing is plugged into the board while testing. I have done some research and tried all the recommended fixes, I even swapped components between the two. Below is what I have tried.

Recapped the non-working board
Swapped RAM between the working and non-working boards
Replaced the SIMM slots. Originals were brittle.
Socketed the ADB and SCSI ICs on both boards and swapped the ICs
Swapped the ROMs and Drive controller/IWM IC. ROMs and drive controller are the same
Replaced the BBU socket
Swapped the BBU between the working and non-working boards
Swapped chassis (Analog board, PSU, screen, etc)

All ICs from the non-working board, work fine in the working board. There is no visual damage or corrosion on the board. I am not sure what else to try. Any recommendations would be greatly appreciated.

 

[MacOfAllTrades]

Have you tried just waiting like 5 minutes to see if it’s just taking a while on the RAM check? Another person had a similar issue with their Plus loaded with 4MB RAM. Took them days of trying things and probing and finally found out just waiting for it to finish its ram check was all it took!

Do you get the startup CHIME?

Have you tried starting it with no or less RAM?

Have you tried pressing the interrupt switch while it’s sitting in the gray screen (should see the sad mac and hear the death chime).

 

[TheBurgerKing]

No startup chime. I have waited about 5 minutes and done ram swaps. I installed 1MB and soldered the resistor. Same issue. The RAM in the machine works fine in other MAC SEs. I havent tried pressing the interupt switch. I will try that tonight. Maybe I will wait a little bit longer than 5 min as well. I will let you know what happens. I appreciate the suggestions.