Hello guys,
I'd like to add two cents here.
Recently, a friend of mine, asked me to repair his GameBoy Micro which didn't charge. I checked all the fuses and EMI filters as suggested in this topic, but all of them showed continuity on my multimeter. Next step was tracing voltages according to
@Ozito diagram (BTW: many thanks for that!) but to my amazement, voltages pre and post the 1 Ohm resistor were missing, not to mention those around the transistors.
I started searching for any useful information but couldn't find anything related to GameBoy Micro so I decided to extend my search to GBA SP and NDS. Here's the breakthrough: several times I came across information related to corroded traces located under the cartridge slot. With nothing to lose, I decided to desolder the cartridge slot on my console. Here's what I found:
View attachment 422579
One of the traces stopped conducting due to oxidation. Guess what? Mentioned trace leads directly to U2 Mitsumi Power Management IC which is responsible for battery charging. By using very thin wire and solder mask, I rebuilt corroded trace:
View attachment 422580
View attachment 422581
Without surprise, friend's GBM started charging the battery again.
In some places, the solder mask had also started to come off - I secured these areas too.
I hope this helps someone, as I found several threads on the web with similar problems left unresolved.
Ps: Stop blowing inside the cartridges!