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820-00426 EMC2910 boot issue

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Scottm1911

New member
This board won't load OS when trackpad connected(freezes in apple logo) and function normal without trackpad
When connected in EFI tpad and keyboard functional normal but no boot OS from SSD or external devices, if i press D to built-in diagnostic and it freezes after 1 minute of test
I will replace tpad+cable but it doesnt help
 
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Scottm1911

New member
UPD. I take 820-4924 schematic, find and check smc pull-ups it's appears OK
but voltage on this lines (SDA SCL) is from 1.8 to 3.3v i don't know maybe it's normal in oscilloscope i have some data activity
After replacement 2 IO Expanders, no result
I think maybe problem in thermal sensing or in SPI lines, who can help with this? I can't find boardview to any force-touch models (820-00426,820-00138,820-4924)
 
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dukefawks

Administrator
There is no info available on these machines, no schematics or BV. This royally sucks and there is not that much you can do.
One thing you could do is compare all pins of the trackpad connector on diode mode to a known good board. Could be corroded trace.
Can you run internal diagnostic when holding down "D" when turning on?
 
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Scottm1911

New member
Yes, I load diagnostics but it freezes when tpad is connected and pass diagnostics with tpad thermal sense error when tpad disconnected.
 
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Scottm1911

New member
UPD. When load recovery and connect trackpad on working machine all works pretty good any time, but when I do anything (click on window or etc) it freezes.
Maybe whose know why on smbus lines voltage jump from 1.8 to 3.3v?
 
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dukefawks

Administrator
Don't use comments I don't get notified.

I really can only say that it must be a corroded trace to the connector. I cannot help you as there are no schematics. Also I have no machines to compare measurements for you.

SMBUS lines will jump up and down, that is the data being transmitted.
 
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