[SOLVED]820-00165 Thunderbolt Issue; Causes system to throttle?

SMMRepair

Member
Repaired a board that had some very minor liquid damage to LP8550 and U3210. Got everything cleaned up, went to test the board, and all is fine except the Thunderbolt port. I noticed that whenever I plug a device into the Thunderbolt port, it causes the unit to slooooowww down and throttle itself almost as if a sensor is damaged. Trackpad movement is incredibly slow (even slower than when a bad trackpad is installed, etc). When I unplug the thunderbolt cable, all returns to normal immediately.

When troubleshooting, I noticed I pulled a U3210 from an 820-3437 board to repair this one; I didn't realize this chip was actually different between the two boards. I replaced the chip with a proper one (from another 00165), and the issue persists.

System Preferences does not show anything connected ("No device connected") when I plug in a Thunderbolt monitor (that I use to test all boards with). Everything around the area looks fine where the liquid spill was.

Any idea what the issue could be? Did I fuck something up by installing a slightly different chip? This is a customer board, so unfortunately they will want Thunderbolt working of course. Any ideas appreciated!
 

SMMRepair

Member
A bit of an update, as I've found out some more information:

The unit WILL WORK on Thunderbolt (without any throttling) at the OS login window. I can connect the unit with Thunderbolt, and the display will be detected and work fine. I log into OSX, and it still works fine (no throttling), however System Information still shows "No Device Connected" in the Thunderbolt info window. If I unplug the thunderbolt cable at this point, and then re-plug it in, it doesn't work any more and I get the throttled/slowness issue. It will only work (and not cause the throttling) if I plug in the monitor at the OS login screen.

Hopefully this information will help in some way. I'm going to try a new test assembly, just in case the SSD is causing issues (I can't otherwise figure how the thunderbolt port would work at OS login, but not in OS). Also, I don't know why the device window for Thunderbolt says "No Device Connected" even as an external display is connected and working (as I had plugged it in at OS login).

Really odd.
 

SMMRepair

Member
Final update: Got this one figured out. Went ahead and replaced U3220 and U3090 and got functionality again. Noticed my diode readings were off on pins 6/7 of U3210 (by around ~.035) compared to a good board, and I guess U3090 was damaged. Anyway, all seems well at this point.
 
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