So, I’ve been assembling another batch
of the ESP32 rainbows. So, the PCBs,
they’re all done by PCB weight. You can
check out a link to them in the
description. They do the initial PCB,
the UV silk screen printing, and some of
the components. And then final assembly
is done here in Scotland where we also
do some QA checks. So, I thought it’ be
interesting to have a look at the three
QA failures and see what’s gone wrong.
So, we have one board where we got no
sound coming out. We have one board with
a dodgy keyboard. So, for some reason,
the touchpads A to G are not working.
And we have another board where there’s
no USB. So, we plug it in and the ESP32
doesn’t show up. So, maybe we’ll start
off with the no sound one. Um, I think
this might be a trivial fix, but let’s
have a look.
So, I do have an SD card here that has
some files on it. So, we’ll just power
up this board.
And let’s try out the video player cuz I
put a video file onto the SD card. Well,
there’s definitely no sound coming out.
So, I think you can hear that. Um, now
all the audio section is around here.
So, that’s interesting. We put a bit of
pressure on the headphone jack and we
get sound coming out. So, I think this
might be quite an easy fix. Uh, let’s
get this under the microscope and have a
look at what’s going on. Um, but yeah,
we can can get sound just by pushing
here. Now, the audio does go via the
headphone jack. That’s how when you plug
in a headphone jack, the audio stops
coming out of the speaker because it’s
rooted via this component. And there’s a
switch inside that disconnects the audio
when you plug a headphone uh jack in.
So, let’s get the microscope out and see
what’s going on. Right. Well, under the
microscope, the issue is pretty clear.
So, this pad has been lifted up, as has
this one. This has become disconnected,
and so has this. So, that definitely
doesn’t pass the solid test. So, the
only connection we’ve got is this one
here. But I might be able to connect the
pad. So I can still see a bit of copper
here and here. So maybe we can actually
join that up and um get it nicely
working. I don’t think we can send this
out to anyone once it’s fixed. The uh
it’s pretty damaged. So what I’ll do is
I’ll just fix it up for fun and see if
the sound works again. So let’s get the
old soldering iron out and see if we can
um fix this. So, let’s squirt a bit of
flux around this situation.
Let’s um let’s solder up these other
ones first because if we can do those,
then it will stay down in the right
position. So, let’s get in there and
melt that.
So, that’s actually stuck down on that
side. Why don’t we do the other side and
then we can have a look at those two
ground pads.
So, it’s actually stuck down.
Um, I wonder if we can now go back to
this one and maybe we can try
fixing it up to the existing ground
plane. There is a bit of copper there.
So, it might work.
Yeah, I think I think we’ve got a
connection there. That might work. So, a
slightly better look in the microscope.
I think that might be a bit better. That
should be good enough. It doesn’t look
very neat. There’s a big blob of solder
on that. Let’s see if we’ve actually
fixed it. We’ve also melted a bit of
plastic. But, as I say, we’re not going
to send this out to anyone. It’s more
for fun. So, let’s power it up and see
if we fixed our problem. Okay, so I’ve
powered it up. Let’s turn it on.
Go to the video player.
And yes,
we got sound coming out. So, I wonder if
we should check the headphone jack. See
if that works. Let’s plug in some
headphones.
So, that’s correct. Sound should stop
coming out of the speaker.
And um I wonder if you can actually hear
this.
I’m not sure where the actual microphone
is. Um,
I can put it up here. So, hopefully you
can hear sound coming out of the
headphones. So, it’s fixed. But, as I
say, we’re not going to send this out to
anyone. It’s not really um it’s a bit of
a bodgege job. So, but we can use this
for spares. So, the board works
perfectly fine or the keyboard works. So
if we um exit from this. So if we go
about get into test mode, then
everything else works. The keyboard is
all fine. Um so yeah,
good spares board. We’ll use this for
repairing other boards if we need to.
So onto the next problem board. No USB.
Now I can see I’ve got it plugged in. If
I turn on, we get 3.3 volts. So I can
see that with that LED and we can double
check with our test points. So if we
just go to these test points here,
ground 3.3,
then we got 3.3 volts. No problem. So
let’s get this under the microscope.
Need to look around here. The USB pins
are these two here. And it goes through
there’s a ESD protection chip and then
the socket. So it’s pretty simple.
Should be quite easy to troubleshoot.
Okay. So, I’ve managed to fit it all
under the microscope. So, we’ve got the
USB socket here, the ESD protection
chip, and here’s the two pins on the
ESP32
that are the USB pins. USB USB pins. So,
let’s just try buzzing this out. So,
let’s uh let’s get a probe on this pin.
So, that should go to the leftmost pin
here.
So that’s fine. And then it should come
through to this pin here, which is also
fine. And then it goes up to a pin on
the USB socket. Um, so that seems fine.
Let’s try the other one. So that’s the
other USB pin. So that should come to
the right hand side of this chip.
It’s coming in there. It should come out
on this pin. Seems to be coming in
there. And then it should go to this pin
here.
And it’s not. That’s interesting. So
actually,
so if we probe the actual pad, there’s
no continuity. So it feels like this end
pin is not soldered properly. Let’s zoom
down on that and see if we can see
what’s going on. Okay. So I’ve really
zoomed in on that IC. Uh, let’s do the
old solid test. It does look like um
some dodgy soldering here. So, let’s
see. That one seems solid.
Seems solid.
That one does seem solid, but the solder
doesn’t look great. Um, in fact, I think
it’s not even on the pad, is it? So,
this I see looks like it’s kind of
missed the pad a bit. Um, so I wonder if
we melt all the solder and try and
reposition it or maybe this is a job for
the hot air gun.
I’ve decided to use my mini hot plate
instead. So, I’ve got the uh the board
balanced on the hot plate. Um, I’ve put
a bit of flux on and we’ll just try and
reflow the solder and then we’ll just
jog the IC into position and get it on
the actual pads. So, hopefully this will
melt soon and we can just move it into
position.
Okay, I think we’ve got that. Seems to
be melting the solder. So, let’s just
give this a quick nudge and see if we
can shift it into position.
Yeah, I think that looks good. So,
perfect. And we’ll take this off the
boil and then do another probe and see
if we’ve fixed it. First off, let’s give
it a quick clean so we can see what
we’re doing. bit of uh 99% pure
isopropyl alcohol just to clean off uh
some of that flux.
Can’t have too much alcohol. It is uh
Christmas after all or New Year. New
Year’s Day in fact here. So uh happy new
year everyone. Anyway, that’s that’s
cleaned that up sufficiently. So let’s
do a bit of probing. see if we fixed our
issue. So, let’s zoom out a bit. So, I
think it was
this one.
And we need to go to
this pin here.
Looks good. And then this pin here on
the USB. Excellent. That’s now hooked
up. Let’s just double check the other
one.
Yep, it’s good.
So, I’m going to program this and we’ll
see if it works. So, we got the board
plugged in. Um, let’s just see if it
shows up.
Oh, there we go. Showing up perfectly.
So, I’m on the ESP32 Rainbow website.
So, we can just go to firmware,
programming an ESP 32 Rainbow. Let’s get
the latest firmware. connect to lab.
Okay, we’re programming
and that’s our program successfully. So,
back on the bench. Let’s power things
up. Our display works and we can
probably remove this. No USB now. This
is going to test mode.
Yeah, everything seems to be working.
So, that’s pretty good. Uh, I don’t know
if we got any games. No, no games. We do
have the video, so we can double check.
Got sound. It’s working nicely. Okay,
that’s board. That board is fixed. Let’s
move on to the next one.
Okay, so on to our next uh repair. Dodgy
keyboard A to G. So, let’s remove the
post-it note and then go into test mode.
Well, in fact, I can’t go into test mode
because the A key doesn’t work. Let’s
use the arrow keys. Go into about and
then Yep. So, keyboard is definitely
behaving in a weird way. So, pushing T
should take us into test mode. Um, but
it’s not. We can actually get into
one of the spectrum modes. So I need No,
that’s not working either. Okay, let’s
get this under the microscope and see
what’s going on. So these are the analog
multiplexor IC’s. Now most of the pins
they’re connected to are along here. So
So I’m looking just visually looks a bit
dodgy along the bottom here. So let’s
get it under the microscope and see
what’s going on. So just looking at this
under the microscope, I think we can see
the issue. The soldering is all a bit
wonky along here. Actually, I can see
this pin here is also looking a bit
dodge. That does seem to be connected.
I think it’s all okay along here and
along the top here. So, let’s just
retach all of these pins along the
bottom here. And that should hopefully
fix our problem.
And of course, finally, bit of 99% pure
alcohol.
Okay, let’s get this powered up and see
if it works now.
So, we’re on. Let’s go into the test
screen.
So, there’s no SD card, but we don’t
really worry about that. Actually, let’s
let’s put one in. Let’s really check if
this does work. So reboot.
Okay. About test. Okay. SD card working.
And do the keys work? So 1 2 3 4 5 6 7 8
9 zero.
Querty UI. Oop work. A works. That was
the fault before.
Yeah, we’re looking good. Keyboard is
fully functional. So, it’s just some
dodgy soldering on the bottom of the
ESP32 module. So, problem solved. That’s
the last of our dodgy boards. So, I
think this one could actually be sent
out. I’ll do another double check of all
the soldering around this area. Just
make sure it is good. But, um,
everything works. Sound all works. So,
not bad.