820-3437 smc_onoff_l 2.1v

[geraymartha]

This 820-3437 powers on when charger is plug , works normally no problems etc , just 1 detail power button don't work , and sometimes after power off becomes dead , and don't want to power on , unless board is take out battery remove , and all plug back in , then when charger is plug works again normally battery holds charge , this board was test on diferent bodys , and keyboards , the only odd thing I find was SMC_ONOFF_L is 2.1v

plz how I can start to trouble shoot this?

 

[dukefawks]

Disconnect trackpad flex and measure SMC_ONOFF again. Should be 3V42. If still low measure resistance to GND, without power of course. Common suspect here would be crap around U5110

 

[geraymartha]

u5110 was replaced already , and the surrounding area is clean and the caps and resistor look very healthy I mesure the resistor is fine , this was done before the post a while ago , diode test is: .514 , resistance to ground 0.70k I wonder if I did that right

 

[smiba]

Could be crap underneath the SMC, try a reflow with a nice amount of flux to hopefully get rid of it.

Does the trackpad connector look alright? C4834 looking alright?

 

[dukefawks]

Resistance to GND is too low. Could be leaky C4834, crap in/under trackpad connector or SMC or another fucked U5110.

 

[geraymartha]

i try the reflow on the smc using 6 of temp and 6 of air , i have the wha900 and I'm not sure the optimal setting to keep smc to being damaged on the reflow , with 6 and 6 voltage still 2.1 , i put flux on the trackpad connector using 6 of air and 2 of temp also I'm not sure if this will be sufficient to flush the connector , voltage still 2.1 after doing that. I'm about to replace again u5110 and c4834 thank you.

 

[smiba]

I have absolutely no idea what "6 of temp" would be in reality. Usually you'd put the air on something reasonably low so the flow doesn't come flying of the board the moment you get the hot air station near it.
"6 of temp" does that usually make the lead free solder melt?

Usually if I really want to thoroughly reflow a SMC I heat it up like I would do with any kind of chip and slightly tap it from the side (not from above as this will ruin the balls possibly) which should make it move and then align again due the flux guiding the chip. I do this on all sides I can reach very softly so the SMC has moved to all the sides a little bit. This also helps the solder to attach to pads that might look less then pristine. Don't tap it hard, you don't want it to get off its pad and attach to the ones next to it. Also keep in mind that this is a pretty aggressive reflow which I only recommend doing when your other last hope would be completely replacing the SMC.

I can also recommend you getting the feel for reflowing SMC's with a dead board first though, I messed up times before I got 'alright' at it.

Do not just replace U5110 and C4834, remove them first and see if the resistance to ground gets above 1kohm before putting them back on

 

[geraymartha]

i remove u5110 .70k still , i remove also c4834 and still .70k to ground , trackpad connector must be clean after a shower of flux right?

i did check on other board and i get like 27k to ground

any inputs voltages that i can check for the smc?

I'm trying again the smc reflow thing.

whats next? if smc , where i can buy? i look on eBay nothing , only 820-3115 , aliexpress nothing :/

 

[smiba]

You need to buy a dead board from china with a hole in it and hope the SMC on there works.
Remove the chip from the china board and reball it before placing it on this motherboard.

Its a pain in the ass but probably the SMC, an internal trace issue or the unlikely scenario of the keyboard connector being broken.
You /may/ want to see if removing the keyboard connector resolves the issue but by desoldering it with hot air you will probably melt it

 

[geraymartha]

i have the china board , and other dead ones , what i don't have yet is solder paste , i just order from rossman store a few days back , i have the stencil but i never did a smc transfer like that , i did install smc before but i purchase already reball , where i can buy the tool to hold the smc while reballing?

and whats the best temp to reball without killing smc?