820-3662 LD, worked for a while after UC now ON-OFF loop

george-a

Member
Hi guys,

this one came with LD which was almost invisible except some patches here and there.. I UC and the board started but would not detect the SSD drive.

I connected a USB boot drive and started from there without issues until the system shut down before completely booting and is in boot loop ever since.

I measured Y1905 and that is getting 0.9 to 1V and also all necessary voltages seem to be present at U1900 but I cant measure 32Khz neither 25MHz coming from the chip.. the oscilloscope shows some irrelevant readings which jump around but not steady frequencies... also pins 15 (SYSCLK_CLK25M_TBT) and 16 looked a bit dodgy ...not shiny like the rest.

BIOS chip area looks good, power comes to pin8.

Could it be the clock chip since its so sensitive to water damage?


george
 

george-a

Member
well that didnt last long - I got lines on the screen, random reboots, SSD not found etc etc.. so I had to reflow the CPU and PCH.

NOW it works and completes the installation of Yosemite OR El Capitan but upon reboot I either get to Recovery and I can only re-install OR it boots again to a fresh installation procedure from the USB stick.

Tried to google this behavior but I only find similar stuff irrelevant though.. i.e. upgrade to El Capitan from Yosemite and have unsupported kexts..

No one seems to have my problem?

Any ideas?
 

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george-a

Member
OK duke, I did not manage to install OSX normally and I had to use RESTORE from Recovery mode/Disk Utility to copy a working installation to the internal SSD. This worked fine with a small glitch.

Upon reboot or turn-on it takes around a minute to detect the SSD and then boot. After that everything seems normal.

see: https://www.youtube.com/watch?v=kQ0cXgLIpjg&feature=youtu.be (65 seconds video)


Since this is still a mystery itd be nice to have some more ideas why its behaving like that.. Unfortunately no spare SSD to check if that is the culprit..
 

jadao

Member
Hi, system will always try to boot last assigned/selected startup disk. It usually takes time to detect ssd when prior to that you use hdd usb boot for testing, live os, or asd efi/os.

Go to system preferences, startup disk and select your booting ssd drive even if it´s the only one.
PRAM should also fix that.
 

george-a

Member
Hi, system will always try to boot last assigned/selected startup disk. It usually takes time to detect ssd when prior to that you use hdd usb boot for testing, live os, or asd efi/os.

Go to system preferences, startup disk and select your booting ssd drive even if it´s the only one.
PRAM should also fix that.


the preferences did it. It now works properly but it seems the SSD has issues - you cant install anything new to it. Works great with different SSD.
thank you!
 
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