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I am still a beginner with electronics and amidst hours of reading I am attempting to diagram out a simple circuit board from a cheap Mario Kart RC car toy that stopped responding to the remote. The toy doesnt work anymore so my main objective is just trying to understand the electronics, i consider it a bonus if I figure out what is wrong with the thing and am able to fix it.

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I cannot seem to identify any of the IC components either because the label is faint or datasheets simply dont exist, or because they are unmarked.

The 16 pin IC looks like a microcontroller of some kind with no marking other than a small dot signifying pin 1. It seems to be connected to a 16Mhz oscillator on the other side of the board. There are three identical 8 pin IC's that are marked with what appears to be an MX prefix (Mitsubishi?), but this doesn't seem to match any manufacturer I have seen thus far. I wonder if they are flash memory of some kind storing firmware. One of these three ICs seem to have two pins soldered together for some reason. There are two motors attached to M1 and M2, as well as a third smaller motor control for tilting the wheels down for hover mode. There is a connector on the back for Try Me mode that connected to the remote while still in the packaging with a three way slide switch that turns it from Off -> Try Me -> On.

Any tips for identifying an unmarked IC or one that doesnt seem to have a datasheet?

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    \$\begingroup\$ In a lot of cases the components will be custom. Reverse engineering could be very difficult, if not impossible, especially for a beginner. \$\endgroup\$ – DerStrom8 Feb 21 '18 at 13:03
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    \$\begingroup\$ See electronics.stackexchange.com/questions/5186/… \$\endgroup\$ – pjc50 Feb 21 '18 at 13:43
  • \$\begingroup\$ @pjc50 Thank you! That is extremely helpful!!! \$\endgroup\$ – maple_shaft Feb 21 '18 at 14:48
  • \$\begingroup\$ Have the same problem with the same board. Some of components cause short on the board. When I do power up, the voltage on the battery pack dropping down from 9V to 0.5 v. I think that device, do not worth the time, to spend on repair. \$\endgroup\$ – Alexandr Belii Mar 28 '18 at 0:50
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These are most likely a microcontroller, a voltage regulator and three full-bridge amplifiers.

First thing to check is connectors, loose cables, and on a cheap PCB base material as this, broken eyelets and traces.

The voltage regulator near the battery input is sure a standard IC, find its number and then the datasheet, then check if there is the advertized output voltage when the battery is connected.

Last thing to check is the crystal. Does the µC has a clock? For that, you need an oscilloscope and a 1:10 probe (or simply hold an 1:1 probe near the crystal pins). You should see an oscillation. If not, or only unreliably, the crystal may be subtly broken due to mechanical shock. It's not unusual for toys.

If all that works but the device doesn't, I would give up. No sense in putting more research into that cheap thing.

(I doubt one of the bridge amplifiers is broken, because then, you simply couldn't move backwards or forwards or steer, but the other function would work.)

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    \$\begingroup\$ Of course, it could be the remote that's at fault. \$\endgroup\$ – Finbarr Feb 21 '18 at 14:03
  • \$\begingroup\$ There's the "try me" switch, which, as far as I understand, makes the thing work without the remote. \$\endgroup\$ – Janka Feb 21 '18 at 14:32
  • \$\begingroup\$ @Janka Thank you for the helpful answer! The Try Me mode only works when connected to the remote over the two pin connector on the back. When you remove it from the packaging, the remote had a long wire coming out of it where it was directly connected to the PCB allowing you to do certain functions while on the shelf. They instructed to cut the wire from the remote so Try Me is no longer functional. \$\endgroup\$ – maple_shaft Feb 21 '18 at 14:40
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    \$\begingroup\$ Ah, ok. To check the remote function, you could reattach the wire and check if it works then. \$\endgroup\$ – Janka Feb 21 '18 at 14:46
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    \$\begingroup\$ Yeah, but you can assure all the non-RC functions are fine when the device works with the cable. So, if it works with the cable: either the remote or the receiver are broken. \$\endgroup\$ – Janka Feb 21 '18 at 15:43

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