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RC transmitter - Absima CR3P - No power

Kikerumbo

Jun 6, 2022
15
Joined
Jun 6, 2022
Messages
15
Hi everyone!

I have a RC car transmitter, an Absima CR3P, that a few days ago, decided not to turn on anymore.

When I power it from the bench PSU, no current is passing. Voltage "gets" to the PCB when I press the momentary switch push button.

I'm an electronics noob, but I attach pictures of what I think are the voltages on the regulators (picture is marked with "EDIT" at the end of the name) and relevant info of the PCB.

Thanks for any help provided in advance.
 

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kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
Where does the power come into the board and what supplies it? Is your PSU capable of delivering the required current? Did you wire it up/connect/use it properly i.e. did you knowingly do anything 'daft' what using it (finger fault)?

Can't see the relationship between the (presumably) power button and the main PCB.
 

Kikerumbo

Jun 6, 2022
15
Joined
Jun 6, 2022
Messages
15
Where does the power come into the board and what supplies it? Is your PSU capable of delivering the required current? Did you wire it up/connect/use it properly i.e. did you knowingly do anything 'daft' what using it (finger fault)?

Can't see the relationship between the (presumably) power button and the main PCB.
Sorry for not being clear and thanks for your answer.

There's a small PCB between the battery and the main board. This PCB has 3 switches and the power goes directly from the battery connector to the connector that plugs into the main board.

The backside of the button PCB has a connector (the biggest one) with labeled wires. It connects to the main PCB at the big connector. The power goes from the battery, to the small PCB, to the main board, then goes to the button and the only voltage that changes is at the ON/OFF wire that comes from the button PCB.

The other smaller connectors are just for switches and potentiometers (throttle, steering... etc).

The PSU should have no issue providing power (30V - 10A max). It has an overcurrent protection, it's set at 500mA, it showed zero current running through and the overcurrent protection didn't go off. Batteries don't work either.

The radio was working until it didn't. No one touched its innards until it stopped working. Could it have been user error? I suppose it could, but I can't find a way. It uses 4 AA batteries and the user has to be a moron to inverse the polarity of four batteries. Maybe the user could break the push button by pushing it too hard, but the button works fine.
 

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kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
Check D5 for proper function.

Trace the wire from the power switch through the cable(s) and the bigger board connector. From the pin on the bigger connector, trace the tracks to the circuitry that performs the power-on function (possibly Q1/Q4). You might have to reverse engineer the circuit to discover how it works though.
 

Kikerumbo

Jun 6, 2022
15
Joined
Jun 6, 2022
Messages
15
Thanks for your answer.

The issue was U2.

0.62€ solved the issue.
 
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