This could have caught fire!
I've been thinking about this a bit more - I probably had a lucky escape here - this could have actually caught fire...
I recently picked up a cheap mini handheld game console from AliExpress. It’s a nifty little red unit that boasts dozens of retro games – or at least it did, until it suddenly refused to power on.
You can get one for yourself here.
And you can watch me try and diagnose the issue in this video:
My first guess was that the battery had died completely, so I tried to power it directly from USB. Weirdly, it did draw some power — around 200 mA — but nothing worked.
The console has a removable rechargeable battery, one of those slim lithium-ion packs originally made for old feature phones. I pulled out the battery to test it, and unsurprisingly it was completely flat – my multimeter read only about 0.03 V (basically zero). A healthy charged Li-ion should be around 3.7–4.2 V, so clearly the battery had been drained to oblivion. Checking the battery terminals, there’s a dead short between them, which explains the dead battery.
These batteries seem to be very popular and keep cropping up in these little arcade machines.
The PCB inside is very minimal, as expected for these inexpensive devices. There’s not much beyond the essentials: a black epoxy “blob” chip (COB) that contains the main game logic, a flash memory chip that stores all the games, a little crystal oscillator, a speaker, and some buttons and wiring. In fact, the design is so bare-bones that the PCB is single-sided (all components on one side and a few 0-ohm resistor links for routing). It’s impressive how these manufacturers cost-optimize everything.
One thing that did immediately jump out - there’s a very obvious burn mark on the back of the PCB.
And flipping the board over we can see a couple of badly damaged components near the voltage regulator.
Tracing the circuit - this looks well dodgy. From what I can tell, they take 5 V from USB, drop it across a couple of diodes, and then feed that straight into the battery! Not a great idea…
There’s only one component on the battery side of the switch, a small decoupling capacitor - removing this got rid of the short.
My best guess is, I had it on charge, the capacitor failed and went short circuit. This pulled a large amount of current through the diodes, burning them out, and then it drained the battery flat.
Jump-Starting the Board
I tried injecting 5 V directly into the voltage regulator, to see if that was working, but it looks like that is damaged as well - I’ve ordered a replacement.
Putting 3V3 in after the regulator does work! The display comes on.
The Console Lives, But No Sound
The only problem is we’re not getting any sound. I tried swapping the speaker, but no joy.
So, I’m waiting on a replacement regulator. As soon as that arrives we’ll do a bit of surgery and swap out the misbehaving one. And then we’ll do something about the battery charging nonsense.
Thank you for sharing this, Chris. What a save! Luck or skill? I’d say it landed in the right hands — someone with both the knowledge and the patience to give it proper care. In a way, the device is now more valuable because of the TLC you’ve put into it. Looking forward to when the sound is singing again too. Warm regards and best wishes.
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