XR resurrection
-
@vulkito Good find, which component was it getting hot?
-
@lia was the max battery management chip (max 14921). I wasn’t expecting that…
-
I reveived the parts! I’ll get to work tonight. Finger crossed!!!
-
Replaced max ic, installed missing capacitor. E16 is gone! Which means that max ic and pic are supposed to be ok.
However, the OW only stays on when plugged. As soon as i unplug the charger it turns off. I see that the area on the top of the balancing connector gets hot, but that’s a bunch of resistors mostly… -
@vulkito Congrats on the progress!
Unplugging the charger causing it to turn off is normal, does it not want to power on at all when the power button is pressed?
-
@lia correct; once the charger is unplugged the ow does not turn on. Which i’m still thinking why could this be possible. The only thing i can think of is that the bms is not allowing the voltage to pass to the controller for some reason (which should be related with comms i think… but that’s a noob assumption xD)
-
And i’m actually stuck on the ics from the upper side of the balancing connector (i want to check them since there is a lot of heat in there). The only thing i can see on the silk screen is M8t, which if i search looks like it is a sOT-23 and these ones have 6 pins, so it is not the same thing. I saw one that has 6 pins but it is a 9V voltage regulator, which i think it is not the same one. Finally i found a 2N7002PS which has M8% marking (% for the manufacturer site code) and is a 60V,320mA Mosfet. This one could be an option but i’m kind of guessing here. Any ideas out there? If it is a mosfet the pins should be grouped (3-2-1 maybe?) i should take a look to that… but tomorrow; time to go to bed xD
-
I actualli saw a post about M8t … hahahaha viva la search!!
-
@vulkito Before that you may want to try manually triggering the BMS into an on state.
The wire harness is prone to damaged cables, if the blue one breaks it loses the ability to power on via the button.On the bms try connecting briefly the blue wire to the black wire. Those being the ones in the below image I borrowed from Reddit.
This will simulate the button being pressed. If that powers up it might just be the harness. @Lemur had similar with the purple wire in this post.If not then it’s likely the BMS still.
-
@lia thanks! I will try that tonight and see how it goes. Something also weird is that when i plugged the charger it showed 100% charged on the app; but i know that it wasn’t at 100% (it’s been disassembled for two months or so)
-
@vulkito I had a problem with code 16 on a friend's board once and that one turned out to be the vp1786 transeiver chip.
-
@lemur thanks! Actually error 16 is gone (hopefully for good!). Now the board only stays on when plugged.
Taking into account that what i´m experiencing now are power issues i decided to not to plug the board again for now (I don´t know if i can burn any other thing) and take a look into the main MOSFETs. SO:
On the left side we have the 240N10F7 and looks good. But on the left side I found what apparently is a 20N08N5 MOSFET that is gone. I took a look into the resistance and are pretty low:
D-G: 2.4k
D-S: 0.2
G-S: 2.4k
S-D: 0.2
G-D: 2.4k
S-G: 2.4kWith these low values I thought that maybe I turned on the MOSFET when measuring on the gate because I have the same resistance between D-S and between S-D, but I put the negative of the multimeter on it to try to turn it off (just in case) and the values are still the same as above. In any case the rest of the values are also pretty low I think; G-S and D-G should be on the MOhms and are 2.4kOhm. I´m not still confident because when I plugged the OW the other day i didn´t feel any of the MOSFETs getting hot and a short as I´m seeing now could turn that component into a frying pan. I should have the short elsewhere.
On the other hand this maybe could explain those power issues. I´ll keep checking things and once checked i will connect everything and short the blue-black wires on the connector and also will measure voltage values on the MOSFETs.
-
Finally the mosfet is gone. I desoldered the terminals and it is actually out. The problem is now that i’m not able to desolder this mosfet out of the board… it is like is bonded! Terminals are ok but no matter how hot i hit it with the air station it doesn’t move
I do not want to damage the pcb even more. Any suggestions??
-
I made it. Heat, flux, more heat, more flux… more heat… and more everything. That was a hell of a mosfet. The solder these guys used is hard to melt, even when cleaning the pads. Well… another month to receive the parts 🥲
-
@vulkito Good job! Those mosfets are soldered on and require a lot of heat. I made sure the two legs were cut off or separated first before unsoldering the mosfet as I didn't want to tear off the solder pads for the mosfet legs. Ask me how I know. Haha.
Fm use lead free solder which is a pain. -
@lemur yeah… one of the legs lifted up a little bit the pad, so this week i’ll have to fix it with some uv resin. I checked the components next to it because i was concerned i destroyed them with all that amount of heat. Looks like those are ok, but… let’s see when the part arrive. This is taking its time xD
-
@lemur I guess lol
I use lead free on my projects since I don't have to worry about getting lead poisoning. I like the IQ level I currently have and have no interest in dropping it.Also if you rip a pad off, I think you could just run a patch wire from the trace to the leg of the chip. That's what I've seen some people do when fixing circuit boards on old computers that had their traces eaten through
113 volts?! I could lick that!
-
@loaffette LOL
I thought on the wire but then i remembered all the problems i had in the past with vibrations on things that move and i will try to repair the pad with epoxy and copper. If it doesn’t move i don’t have to worry. On motherboards that are usually static there is no problem, but i’ve seen broken cables just due to vibrations, which is a pain -
Guys… do you recommend solder paste for the big pad of the mosfet? I saw that the melting temp of the solder paste is 183C (361F), which i think is safe enough, but maybe those mosfet get really hot on normal conditions and i don’t want to screw it up
-
@vulkito Definitely, solder paste
