Flashing Amp meter on Switch

Hello dear Fix gurus.

I bought a broken Switch off eBay in the hopes of playing around with it and ideally fixing it.

It had a damaged charge port with several pins either missing or bent 90° and shorting out several others. When the bent pins where removed it still charged with about 0.46 Amps and the battery voltage was increasing. It wouldn´t turn on however.

Further tests showed shorts around P13USB but no shorts in the “usual” areas of the board/around the other major chips.

I now replaced the USB port (and verified that the pins are soldered on firmly with a test board, as far as possible, e.g. for the visible line of pins thats not covered by the port)

I also replaced P13USB with one from a donor board that didn´t show any shorts in that area. I believe it to be soldered on correctly (I´m still a novice in SMD soldering) but can´t guarantee that or that the chip is 100% ok.

Anyway… now that both parts have been replaced the behavior of the switch is actually worse.
If I plug in the amp meter now, all I get is a flashing screen on the amp meter and even that only in one direction. The switch itself still isn´t turning on.

I´m not seeing any further shorts. The one on P13USB is gone now, none around the BQ chip or M92 either.

At this point I´m pretty much lost. I assume that the “inner” row of pins of the USB C Port probably isn´t soldered on properly, that would explain why I´m only getting the flashing Amp meter in one direction.
But other than that and maybe assuming that the “new” P13USB is also faulty I have no idea what could be going on.

So if anyone has an idea or suggestion what to do… I´d very much appreciate it :).

Many thanks in advance,

the new guy

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You should Always replace M92 if the USB Port is damaged, it’s a charging IC and often goes Bad by broken or shortet pins.
The caps arent Always shorted, even the Chip is Bad. For testing, you can just remove the M92 and see if it boots without it (an error message will Show up then).

I also think, but not 100% sure, the switch will Boot without PI3 as well, but will only charging from one side and of course does not Dock.

Your flashing Could indicate a Bad or wrong soldered PI3.

Thanks Zyrex for your tips.
I removed the P13 and the Amp meter is still flashing on one side and nothing on the other.
I don´t have a M92 that I know is good so I´ll order some and try to replace it.
Whats puzzling me is that with the replaced port it seems the behavior is worse than before I replaced the port (as it was at least charging at 0.46 Amps before).

Usually 0,46A can be causes by many things, one is a Bad PI3 Chip, other reasons can be a bad NAND or CPU.

What happens if you plug the switch into your PC with TegraRCMgui open?

Will it detect an RCM device or not?

Since you have the problem with the flashing, Maybe you should replace PI3 again.

If the USB C breakout Board reads fine, there is no reason to change the USB Port, but you can try it again of course.
How did you soldered it?

For me it works best, that after removing the old Port, I Clean the 2 bottom holes with solder wick. Then I tin the pads with leaded solder.
Then I only apply heat from the bottom, and If the top holes are melted, I Insert the New Port with a bit pressure from the top, hold it a few seconds and moving the hot air under it in circles. Then remove the hot air but still aplly some down pressure until its solid.

Unfortunately the 0.46A was before the port replacement. Now even thats not happening anymore.

The cap below P13 was shorted and the short went away when I removed the old chip. So I assume it was indeed bad. Its acting normal now but of course this isn´t a guarantee for a working P13…

I don´t know if there is any way to test the CPU or NAND. The “CPU cap” under M92 is good.

Unfortunately it´s not showing up in RCM mode. I was hoping for that one as well as it has an appropriate SN to expect it.
I can say for sure, because of the breakout board, that the port is soldered for one side. As the other row of pads is below the port I dont know how to test these for continuity.
I soldered if using hot air from the bottom. Pretty much like you described tbh.

Yeah the 0,46A can also Happen if there are no shortet caps around PI3.

If it’s not appear ing in RCM it’s acutally a good sign, since often this means the NAND is Bad and you cant replace or repair it.

I would remove bot PI3 and M92 and See if it will Boot with a good battery

I´ll be dammed! I removed the M92 and it did indeed turn on! Shows error 2101-0001 now but i guess thats to be expected for only half a switch :).

Whats the resistance to ground on this cap, measuring the left side?

yeah thats usually the error without M92 :smiley:

Its measuring 52 Ohms.

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Yeah thats completelly fine. By measureing this cap, you can make sure your SOC is good. On normal Switches it should be at least 40 Ohm’s.
On lites it is way lower, around 15-20 Ohm’s.

I would think a flashing amp meter indicates a short beteen 5v and ground? Worth testing with a multimeter. If so i would susoect the new port.

Thats possible. But depending on the amp Meter and the used charger, it could also be just the M92.

When I use the offical charger with the amp Meter, the Meter will only turn on when there is current flowing, othetwise it’s completelly of. With 5V charger, it says on All time.

Ok. Quick update here. I replaced the M91 and P13 and the device is booting normally again.
Unfortunately I still have some issues with the USB port…For some reason I seem unable to properly solder that port on… And now I have annihilated several pads during my several tries to get it on…
I´m going to go throw up now…
Not sure if I´ll be able to get these traces fixed. I might. But then I´d still be back at square 1 in terms of getting that port on…
Anyone from Germany interested in some trace repair work? :slight_smile:

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