Tiptoi

[VooDust]

The tiptoi is a battery-powered (2x1.5v) kid's toy.

My device has stopped working (it won't turn on) and I wanted to check if there were any loose wires, because obviously the device gets dropped a lot.

But I was not able to identify any loose cabling, nor any signs of "burn" or wear.

However I spotted this cylindrical component, it's labelled "Y1" and has some brown goo over it. Now I wonder, do you think that stuff could be glue or is it a leaking component? I measured precisely 1.0 MOhm across its pins.

Do you have any idea what this thing is and if it may be defective? It was tilted to the side, laying next to the IC. I bent it upwards for the photo.

[jackthomson41]

It looks like a capacitor to me, but not sure exactly. Can't you read anything written on it. It's base looks black I think its burnt out. It happened to me once with ESP8266.

[Twoflower]

That cylinder is a crystal and often glued to the PCB (the brown stuff) because of the thin wires. So that's most likely not the problem you're looking for.

Capacitors are labeled with C not Y.

But I think there is something missing on the other edge og the PCB. K2 seems to be gone 

[goaty]

I had repaired one for a neighbour, the Inductor was broken off of the switchmode power supply inside the TipToi.
It is a small greyish rectangular component (Inductor) probably labeled "L1" or something.

[Twoflower]

Looked up some pictures. The K2 seems to be correct, as this is a switch on the back-side. The odd looking solder-blobs there looked like a part was ripped off.

[thinkfat]

"Thou Shall Check Supply Voltages"

[VooDust]

Looked up some pictures. The K2 seems to be correct, as this is a switch on the back-side. The odd looking solder-blobs there looked like a part was ripped off.

correct, the switch is on the back side. The solder blobs are the + and - wires from the batteries that are soldered from the back, too.

[VooDust]

I had repaired one for a neighbour, the Inductor was broken off of the switchmode power supply inside the TipToi.
It is a small greyish rectangular component (Inductor) probably labeled "L1" or something.

L10 (written upside down, located bottom center) seems to be still here:

[VooDust]

According to this there's a fuse: https://github.com/entropia/tip-toi-reveng/wiki/Hardware

It reads 0.3 Ohms so I guess it's OK.

[goaty]

So then check the voltage of battery to the switchmode chip U5 and if there is voltage after it.
Before is probably 2x 1,5V fter is maby 5V.

[VooDust]

So then check the voltage of battery to the switchmode chip U5 and if there is voltage after it.
Before is probably 2x 1,5V fter is maby 5V.

The battery pack voltage is 2.74v

I could not find info about the pins of the switch mode chip, but if you look at it like in the image above they read like this: (C3 3B are the markings on the chip)


while pressing the power switch:

      3.3v
_______|________
[   "3"  "B"   ]
[___"C"__"3"___]
  |    |     |
 1mV  3.3v  2.6V

[Twoflower]

That 3.3V looks fine. Most electronics today uses 3.3V (LVTTL), not 5V (TTL).

You write while pressing the power switch. Does that mean the 3.3V vanishes if you let go the switch?

Also can you visually check that the solder joint of the capacitor close to the black battery cable is OK? On your picture it looks like that there could be a crack.

[thinkfat]

If the voltage goes away when you release the button, it is likely that the micro controller doesn't boot. That crystal Y1, was it still glued down? If it's flapping around, it might be broken...

[goaty]

I found this schematic when googling. May not be fully correct, but it gives an idea:
https://lists.nomeata.de/archive/tiptoi/attachments/20161220/e0e751c1/attachment.pdf

[thinkfat]

I found this schematic when googling. May not be fully correct, but it gives an idea:
https://lists.nomeata.de/archive/tiptoi/attachments/20161220/e0e751c1/attachment.pdf

That looks a bit weird indeed, especially around U5 and U8. Pretty sure L10 belongs to U5, which is likely a boost converter, and U8 is an LDO linear regulator which is probably active when the device is plugged into USB. I don't see the mandatory diode, but it could be integrated in the regulator.

[VooDust]

You write while pressing the power switch. Does that mean the 3.3V vanishes if you let go the switch?

Yes and yes. I thought that's normal but if the toy were working then the 3.3 volts should stay?

Also can you visually check that the solder joint of the capacitor close to the black battery cable is OK? On your picture it looks like that there could be a crack.

I inspected the capacitor and there is no crack. It's a reflection on the photo.

I tried testing the large capacitors with a Multimeter and a DC voltage source. Only one of three Caps is able to hold its voltage, but I think this is because the caps are still inserted on the circuit, i.e. they might lose their load instantaneously because of the other components it's connected to, right?

edit: My multimeter has a capacitance measurement option. All 220 caps measured OK, with the exception of one that measured 300uF instead. In circuit, that is.

[VooDust]

If the voltage goes away when you release the button, it is likely that the micro controller doesn't boot. That crystal Y1, was it still glued down? If it's flapping around, it might be broken...

No, it was not glued down when I opened the toy, i.e. the glue had come off previously.

The last two weeks I was contemplating buying an Oscilloscope, I think I finally found a reason to go buy one! 

Or can I test the crystal by hooking it up to an Arduino? Let me google this...

[Twoflower]

I expect that the power should stay at 3.3V after pressing the on button. The schematic is a bit unexpected, but the controller should keep the electronic switch (Q78 and Q8 via Q10) enabled by set pin GPIO15 via D6 after 'booting'. The path D6 is parallel to D7 which is the power switch. So it really seems that the controller refuses to keep the circuit enabled.

There is a pad labeled VDDIO. Can you measure the voltage while and after pressing the power button. There's also a GND-Pad you can use for the - lead of the multimeter.

It also seems that the pen can be powered by the USB-connector (via U8). It still needs some 'support' from the controller via GPIO6. But it's probably worth a try. Does it show up if you connect it to the PC?

Regarding the crystal: They're reasonably robust. I don't think that this one is the reason for the problem.

[VooDust]

I expect that the power should stay at 3.3V after pressing the on button. The schematic is a bit unexpected, but the controller should keep the electronic switch (Q78 and Q8 via Q10) enabled by set pin GPIO15 via D6 after 'booting'. The path D6 is parallel to D7 which is the power switch. So it really seems that the controller refuses to keep the circuit enabled.

There is a pad labeled VDDIO. Can you measure the voltage while and after pressing the power button. There's also a GND-Pad you can use for the - lead of the multimeter.

It also seems that the pen can be powered by the USB-connector (via U8). It still needs some 'support' from the controller via GPIO6. But it's probably worth a try. Does it show up if you connect it to the PC?

Regarding the crystal: They're reasonably robust. I don't think that this one is the reason for the problem.

It did not power up via USB either.

Unfortunately, I think I bricked the pen even further by fiddling and trying - now I cannot get the 3.3v on the switchmode IC, but rather I read a leakage voltage of 300mV regardless of pressing the power button and other measurements seem to be hit and miss.

Thanks guys, I really appreciate your help and I have learned a lot about basic component testing in this thread. I'll have to buy a new one, I'll keep the old one around though for spares