820 00850 Macbook Pro Slow performance

[Stevie_belfast]

Hi guys

820 00850 board here, clean, no previous repair.

Had a short on PPBUS, I found the problem, was shorted cap C8150, replaced and macbook boots.

Problem is its very slow.

It would boot to login screen eventually, but mouse and keyboard very erratic and slow to respond.

When I tried Internet Recovery, it takes a few hours then fails on 2005F error.

When I try to boot from USB stick, it lets me select the stick, then just a blank screen and goes no further.


I restored using DFU mode but still the same.


Seems like maybe another problem on the board that's causing it to be slow?

Like CPU is throttled.


Any help greatly appreciated.

[Aliencomputres]

Re: 820 00850 Macbook Pro Slow performance

heloo

[Stevie_belfast]

Re: 820 00850 Macbook Pro Slow performance

heloo

Cheers but i've reset NVRAM a load of times.

[reformatt]

Re: 820 00850 Macbook Pro Slow performance

Probably missing sensor data. You can prove it by going into diagnostics on boot up (IIRC you get a PFM error code). I would be eyeballing the Thunderbolt Air sensors IC's U5850/U5860 (around and underneath them) primarily as they are at the edges of the board. U5870 would also be a good candidate too, as it's just above the cap you replaced.

[Stevie_belfast]

Re: 820 00850 Macbook Pro Slow performance

Probably missing sensor data. You can prove it by going into diagnostics on boot up (IIRC you get a PFM error code). I would be eyeballing the Thunderbolt Air sensors IC's U5850/U5860 (around and underneath them) primarily as they are at the edges of the board. U5870 would also be a good candidate too, as it's just above the cap you replaced.

Thanks for the info and reply,

Forgot to mention, I did replace U5870 from info gained from searching for something similar to this problem.

Cant get into diagnostics mode either, gets as far as entering wifi password then just hangs on blank screen.

I'll have a look at U5850 & U5860, cheers reformatt.

[Stevie_belfast]

Re: 820 00850 Macbook Pro Slow performance

Changed U5850 & U5860 but still the same awfully slow performance.

[reformatt]

Re: 820 00850 Macbook Pro Slow performance

No signs of corrosion then? These are just the thermal sensors, there are others for power as well. I'd be looking at these sections for any tell tale signs of corrosion, maybe even use a thermal camera to identify any hot spots out side of the power supplies and CPU.

PROCHOT can be asserted by the system management or by the CPU itself for throttling. Throttlestop is a Windows utility that I've used to debug this stuff on Windows machines, not sure what's out there for MAC's. In theory you could install Windows on this MAC but I'm sure it would be painful.

[Stevie_belfast]

Re: 820 00850 Macbook Pro Slow performance

No signs of corrosion, very clean board.

I don't have a thermal camera but i'll look for hotspots the old fashioned way.

Yes a windows install would be very painful.

Ok, i'll keep on at it.

Thanks for the reply.

[Stevie_belfast]

Re: 820 00850 Macbook Pro Slow performance

Ok, strange one this.

Getting hot around QB300, and the caps above it, C7006, C7008, C7009.

Checked for shorts but none that I can find.

All 4 USBC ports work fine and switch to 20V



Other side of the board around Q3100 doesn't get as hot.

[Stevie_belfast]

Re: 820 00850 Macbook Pro Slow performance

Update, just incase anyone else has a performance problem.

Found a dislodged cap, C7908, on PP3v3_G3H_PMU_VINTRC_R.

sluggish poor performance is now fixed and it seems to be running fine now.


Now just have to get past the 2005F error in recovery which seem to be due to WiFi issues.