So, I got this um red mini handheld game
thing from AliExpress recently. Uh it
worked briefly and now it appears to
have completely died. So, I think not
sure which way is on or off, but uh
neither way does anything. So, let’s try
and find out what’s gone wrong. So, I
think first thing to do is see if it’s
actually um taking any current. So, I’ve
got my USB tester here and somewhere I
have a cable. There we go. So, let’s
plug this in.
So, that’s interesting. We do appear to
be drawing around 200 milliamps. So,
does it do anything when I turn on and
off? Absolutely nothing. So, it’s
drawing current, but the onoff switch
doesn’t do anything. Um, so that’s kind
of interesting. Um, there is a battery.
So, let’s have a look at the battery.
See what’s going on with that.
So, it’s one of these old cell phone
type batteries that seem to be being
used a lot for these kind of little uh
game type things. It was in the previous
one I took apart. Um, so let’s go on to
voltage DC.
kind of kind of awkward. Come here.
So, our battery voltage H
0.27
volts. So, 27 mill volts in our battery.
So, this battery is completely flat. Um,
that’s interesting.
Let’s take the battery out. I wonder if
uh if it works without the battery.
Let’s plug that in. and
still get nothing. And we’re still
drawing 200 milliamps. So, definely
something going on, but it’s definitely
not working. What I might try doing is
just powering it directly from these
battery terminals. So, let’s see if we
can wire that up. Move that out of the
way. Um, I got my power supply here.
Let’s just um Yeah, let’s wire this up.
So, which one’s plus and minus? So is
that plus
and uh that one is minus.
Okay, let’s give this some juice.
Quite loud. Got a fan in here that uh
seems very noisy. Let’s turn that on.
Hello. Where’s my output voltage?
Ah, well that’s interesting.
You can see this uh constant current has
been limited immediately. I did set this
quite low, but um let’s see. Yeah.
Well, that’s that’s no good, is it?
We’re not getting uh anything. Um so, I
think maybe there’s a short there.
That’s uh let’s have a look.
Certainly didn’t want to power it. So,
bring in the multimeter and
switch to continuity.
see what’s going on.
Well, it’s dead short, so that’s not
going to work, is it? Well, let’s open
this up and see what’s going on.
Obviously, something’s gone horribly
wrong.
Okay, well, that was fairly painless.
Let’s try not to lose the screws. um
stick them in this little compartment
here.
And you can see here the problem with uh
directly putting screws into plastic.
All the plastic’s being worn away by
this screw. Well, I can see something
interesting straight away. I mean, that
doesn’t look right, does it? We
shouldn’t have a big burn mark on our
PCB. Let’s uh let’s get the PCB undone.
Well,
look at that. That’s not a very happy
IC, is it? That’s completely burnt up.
Um, I suspect that’s probably some kind
of voltage regulator. I mean, there’s
not much on these PCBs. So, here we have
the blob chip. Got some flash storage.
Crystal got kind of clicky button.
Speaker. Um, yeah. Not a lot to these
things, is there? Well, that looks like
the uh thing that’s gone horribly wrong.
Looks like our voltage regulator has um
burnt itself up to a crisp. Um,
interesting. So, what if we just remove
this and then um
try applying voltage directly and see
what happens. Since we’re about to look
at a whole bunch of PCBs, let’s do a
shout out to PCB weight, who do all the
PCBs for this channel. Check out our
link in the description. They’re really
great. So, unfortunately, my microscope
stopped recording. So, we lost quite a
lot of footage. However, there were some
interesting findings. So, if we look
here, this is the burnt area of the PCB
from the other side. Now, there was this
interesting lump of plastic. Um, that
confused me slightly, but then I
realized it was actually one of these
foam spacers that had got really hot and
melted.
Now, what I’ve seen so far is there’s a
complete short on the battery supply to
the um to the input of this switch. Now,
so what we see is on this pin here,
there’s a dead short to ground. So this
test pad here shorts to ground
completely. Um so that’s why the battery
is completely flat. Now I imagine that’s
why these two components burnt out. This
one was kind of okay. So this was a
diode. I believe this one might have
been a diode as well. So it’s a
interesting circuit. So we have the 5
volts coming from the USB. Comes along
here. There’s a bit of decoupling a test
point. comes here, comes across one
diode, and then comes across another.
And then this connects through to this
trace, which goes up here, another test
point, goes into this pin of this
switch. When you turn it on, these two
pins are connected, and it supplies
voltage to the pin here, which is the
input pin of this 662K 3.3 volt voltage
regulator. And that’s the output pin
with a couple of decoupling capacitors.
So if we trace this um this trace back.
So that’s coming from the 5 volt supply
through a couple of diodes. This goes
all the way around all the way around.
And eventually
if you follow the trace all the way
around the PCB, there’s a couple of um
jumper zero ohm resistors. It’s a
singlesided board. They’ve gone for
maximum cheapness here. comes around
here and eventually we end up at this
pin which is the positive pin of the
battery. So somewhere around here there
is a short. So it could be this um this
capacitor maybe. Um
I think that’s the only real component
we can see on this trace now. So what
I’m going to do you see I’ve put a blob
of solder here on this test point. So
this is the input to the voltage
regulator. So, what we’ll do is try
feeding 5 volts into this. See if we get
3.3 volts on the output of that. So, I’m
going to do that now. I’ll tack some
wires on. So, a wire here for ground and
a wire here for 5 volts. And let’s see
what happens.
Well, slightly disappointing. So, we do
have, if I measure
our little tact things, that’s uh five
watts coming in here. Unfortunately,
coming out here on the output, I’m not
getting 3.3 volts. So, this um this IC
here should be a 3.3 volt regulator, but
um I’m only getting five 1.5 volts. So,
it should be giving 3.3 volts, but it’s
not. So, let’s try something else. I’m
going to move this wire I’ve tacked on
from the output from sorry, the input,
stick it on the output. So, I’m hoping
I’ll find a test point somewhere that I
can just Yeah, I can just connect it to
here and then we’ll just inject 3.3
volts straight into the system. So,
let’s try that quickly. So, let’s just
put a quick blob of solder on here.
There we go. And then we’ll just move
our little wire
from here
and we’ll put it over here.
Try not to short various things. Left my
wire a bit too big.
Okay, that’s kind of connected. Let’s
see what happens now.
Connect it up.
Okay interesting.
So, we do have
the blue light showing it.
Not getting any sound coming out. I’d
expect some sound.
No sound. Let’s check the voltage. Make
sure we do have 3.3 volts coming in.
Yep. 3.3 volts.
Not looking very promising. So, I’m now
injecting 3.3 volts directly. And
there’s nothing coming out. What I’m
going to do is reconnect the screen. See
if anything’s happening at all.
Oh my goodness me.
Wow. Okay. I mean, I’ll have to zoom out
quite a bit for you to see this. I’m
going have to switch to the other
camera, but actually we have action.
So, we are actually getting things
showing up. So, we’re back on the uh
main camera, and as you can see, we’re
injecting 3.3 volts straight in, and
it’s all working nicely. Well, it’s
working to a certain extent. Let’s uh
let’s just move this out the way. Put
some buttons back on.
One set of buttons.
Another set of buttons. And then we got
these buttons down here. And what come
desoldered? Let me solder this wire back
on quickly. One moment, please.
Okay, back in action now. Then let’s
make sure we get English.
Then we go down. Oops. Yep.
Down. And then one of these is start.
Start. Start. No,
that one. Start. Okay. So, hold of these
games. Um, let’s just do Super Mario.
Super Mario Brothers.
Okay. So, that’s working nicely, but we
have no sound, which is somewhat
annoying.
And I Yeah. Okay. Okay. Well, I don’t
know how to play this, especially with
the buttons all over the place. Um, just
reset.
There’s no there’s no setting to um
change it to no sound. Uh, I do wonder
if maybe this speaker has gone wonky. It
does seem soldered up. Okay. Uh,
actually, I’ve got some speakers
somewhere. One second. So, let’s quickly
desolder this one, which I think
probably isn’t working. Oh, maybe it’s
maybe the speaker’s fine, but something
else has gone wrong. But it seems likely
it’s going to be the um the speaker. So,
why won’t you do solder? That’s one.
Horrible solder on this board.
Okay, that’s two. Let’s put a bit of
leaded solder on.
Okay, that’s one bit.
Another bit. Nice bit of leaded solder.
Much better than the yucky stuff, right?
I don’t think it really matters which
one’s positive or negative. Let’s just
do this one.
This one can go in here.
Okay. Not the greatest job, but
go and then
that one should go there. I’m still not
hearing any sound. That’s very
interesting.
No sound at all. Let me got the volume
turned down.
N
interesting. Well, further
investigations required on the actual
sound then. That’s very intriguing. Um I
would have expected something to come
out. I can see a little component here.
We may have to get it under the
microscope to troubleshoot sound again
because I wonder if that’s gone and
that’s why we’re not getting any sound.
Actually, let’s just disconnect the
power. Do a quick continuity check while
we’re here.
See if that’s the problem. So,
looking at the traces.
Um gosh, where is where are these traces
going? That’s going there.
I think that might be coming to the
positive one.
Yeah. So that goes to that end. Does it
go to the other end?
No. Interesting.
There is nothing going through that.
It’s probably a resistor. Actually,
maybe it is just a resistor. Let me just
measure the resistance.
Maybe they had it way too loud and had
to do something about it.
I don’t think that is a resistor. I
think
that’s doing nothing.
See?
Oh, maybe it’s a 1k resistor.
Hard to measure.
Okay, so that is a resistor
and it is
if I can measure it successfully.
Looks like it’s 20 ohms maybe or 15
ohms. It’s very tiny. Well, okay. We
need to investigate the speaker issue
then. Something else is going wrong with
the speakers. Well, we’ll do that later
once we fix the rest of the board. Um,
sound should work, but we’ll do it get
it under the microscope. See what’s
going on. Why do we have no sound? We’ll
find out later.
Now, I just got to thinking there is
actually only one component on this long
trace from the battery. It’s this
capacitor here. I think we should try
desoldering this capacitor and see if
our short disappears. So, let’s power up
the soldering iron and see what happens
if we remove that. So, we’ll just put a
bit of leaded solder onto this and
hopefully we’ll be able to just
scoop this capacitor off. There is a
massive ground plane, but there we go.
That’s our capacitor removed. If we can
get it off my soldering iron.
Okay, let’s just clean this up a bit.
Right now, let’s see if the short has
disappeared. Maybe it’s just the
capacitor that failed and then blew
everything else up. So on continuity,
let’s test these two.
There is no short. Okay. So it was just
that capacitor which I’ve got here. Um
let’s bring this poor fellow back into
the picture.
So there’s our dodgy capacitor.
Let’s just see. Is he shorted?
Oops. Well, he’s he’s vanished now. Oh,
there he is. Okay, let’s bring him back.
Where’s he gone? Bloody thing.
Okay, found him. Let’s uh let’s grab
him. Put him back where we can see him.
There you go.
This
Let’s see. Is this little capacitor
shorted? I suspect it is. Let’s try and
do this without him flying off the
table.
Oh, maybe not
kind of far. It keeps Oh, jeez.
Well, anyway, if we go back to here, we
don’t have a short now between the
positive and the ground. So, that’s
disappeared. No short there. Let’s
double check. Got um got that there. No,
no short at all. Oh, there’s the
capacitor. Found him again. I am going
to measure this capacitor and determined
to actually measure is this capacitor
shorted. So let’s come here. Let’s move
him into a shot. Okay.
Come on.
Well, he doesn’t seem to be shorted.
No, that’s no short at all, is there? My
multime Oops. My multimeter is not
beeping at all.
I wonder if this was just some dodgy
soldering.
See, we come here.
Oops. I mean, there’s a small beep and
then um it stops, but I don’t think it’s
shorted. That’s very interesting. I
wonder
was it just some really nap soldering
right here that was shorting these two
together. It didn’t look like it, but it
is entirely possible. Um anyway, the
soldering is pretty bad, but I’ve got a
replacement. I couldn’t find one in my
bits, so I got a replacement um voltage
regulator coming. But now the uh now the
shorts disappeared. So there’s no if we
use this test point check with ground,
there is no short. So that was the
underlying problem, but the uh the
voltage regulator has blown as well. So
that’s not great. We’ll um we’ll check
what’s going on with that. And I just
realized I was measuring the wrong
thing. It’s uh it’s this test point. So
that test point and ground. There are no
shorts now. So that’s great. Um yeah, so
interesting circuit, but uh we’ll get a
replacement for the voltage regulator. I
will do something about the battery
charging. I don’t think you should just
use a couple of DIYs for battery
charging. That seems exceptionally
dodgy. So, we’ll fix that as well. Um,
yeah, component should arrive soon.