820-4924: Flashing folder and locks up till SMC reset

Any suggestion on this issue having me stumped.

Boots up to question mark folder and gets stuck when I attempt to go into aht or even verbose mode. At this point it would require multiple SMC reset before I can boot up again. Tried reflashing efi chip with clean bios file using CMIZapper medusa 2 and it keeps giving me an error during the flash process. Errors are never the same. When I attempted cleaning the me region, it errors out because it can?t clean the me region.

I went ahead and purchased another already flashed efi chip with the same outcome.
 

2informaticos

Administrator
Staff member
Maybe pin 2 goes low (or fluctuates), but the other three should be high.
Did you reflash it with Medusa, or external programmer?
If Medusa got errors, must try external to discard.

Disconnect external SSD and try your USB test OSX.
If the same, try then some Linux, or Win10 live versions...
 
Yes Medusa got error about 80% into the flash but was able to retry and finish the flash as it continues from where it stopped.
I?ve also tried external hdd with osX on it and it hangs at the Apple logo, no progress bar. Same with ssd removed.

Going to create a windows 10 external drive and test this. Will be back with result.

THank you.
 
I thought it may be the Medusa, so I tested on another known good board without issues. I also contacted the guy that makes the Medusa who sent me the latest rev. It too ends with the same outcome. The new rev doesn?t even attempt to flash, it immediately gives an erase error.

Regarding external flashing, what chip adaptor would you suggest cause I?ve tried 3 different soic8/sop8 test clip, they always give me chip not seen errors. I?ve confirmed all the pins on the test clips are making good contact. I?ve only been able to successfully use it once.
 
Thanks for that link/method for flashing chip, it worked, unfortunately it didn't fix the issue. Also the customer got had to leave the country or something and wanted is system back, so can't work on it anymore.

thanks for all your assistance.
 
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