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Niquan

need help hacking those tiny rc-cars

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Hello!

I stumbled over this special project to hack the transmitter of these tiny rc-cars to improve the range. To do this, I have choosen to use the way with the zener- diode and a clone with TX-2 IC.

Unfortunatly it's not working. The car seems to be charged up and the LEDs indicating an activation (pressing a button) light up each time. Just the car shows no reaction.

Does anyone know, what went wrong? what can I check to find the problem?

thanks for any hint.

Niquan

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Ref: http://www.rc-cam.com/microszr.htm

After the 9V modification, Pin 9 of the TX2 chip should have 4.0VDC to 5.0VDC on it. If higher than 5.0V, the chip will be damaged. If lower, the transmitter might not operate correctly (low voltage).

If the voltage looks correct, then the transmitter's RF amplifier is probably not working. It may be due to an incorrect wiring of the 9V modification (only pin 9 should be cut away from the adjacent trace), or it could be due to the high 9V operating voltage (RF Amp oscillator stalled).

Take the modification off and see it everything works correctly. If it doesn't, then something has been damaged. It it works, and you believe your modification was wired correctly, then your Tx is not compatible with the higher voltage. Try something less, perhaps 6VDC (4 alkaline cells).

Please be aware that you can NOT recharge the car from the transmitter's charge port if you install the modification. The car might be damaged if you do.

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Hello Mr. rc-cam

Okay, I found my multi-meter, and measured a little bit around. The voltage at pin 9 is about 4.1 VDC, the output voltage at the charger is nearly 10 VDC. I think, I used not the best-quality powersupply.

I wonder, why the voltage over the oszillator- quartz seems to exceed 30 VDC! Is this just a analog-voltmeter effekt or a puzzle-piece of my problem? Sometimes the LED of the charger lights up, although theres nothing connected to the 'charge-port'.

The modification wiring should be correct, and I cut only pin 9 away from the supply by grinding off the copperfoil.

If it helps, I can provide some digicam-images of the modifications.

( www.niquan.com/transmitter2.jpg )

A lower voltage doesn't show any effect.

Erm... just for the case... what would be the part of the car, which would be damaged if charged with 9 VDC? ;o)

best regards

Niquan

Edited by Niquan

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The voltage at pin 9 is about 4.1 VDC, the output voltage at the charger is nearly 10 VDC. I think, I used not the best-quality powersupply.

The measured 4.1V is fine. But 10V at the charger output does not make sense -- you should be using a 9V battery! If you have used a power source greater than 9V you many have damaged some components.

I wonder, why the voltage over the oszillator- quartz seems to exceed 30 VDC!

You cannot use the voltmeter near the RF circuitry. It will be confused by the RF signal.

Sometimes the LED of the charger lights up, although theres nothing connected to the 'charge-port'

The charger feature is not available after the modification. Do not use it!

The modification wiring should be correct, and I cut only pin 9 away from the supply by grinding off the copperfoil.

That is the correct way.

A lower voltage doesn't show any effect.

That is too bad. Your best course of action is to remove the modification and restore normal operation.

what would be the part of the car, which would be damaged if charged with 9 VDC?

First the car's battery would be harmed. The car's electronic circuitry can also be damaged. The extent of the damage all depends on what the power source was, its voltage, and available current.

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Hello!

I modified a second transmitter, and this time it seems to work. I added one piece after another and always checked the functionality before adding the next. First I added the resistor, then the zener-diode and then the capacitor. At last I cut off the original wiring of pin 9.

First I tried 4 V and then rose the voltage up to 9 v, and it worked fine!

It seems that the poor quality of the used AC/DC adaptor for power supply (provided over 12 V when I expected 9 V) toasted both the transmitter and the receiver. :o(

This modification increased the range from lousy 2m (6 ft) to poor 12m (35 ft).

What else can I do? I found a small cap which seems to be added later. My idea is, that this cap is a kind of 'cipple cap', but I'm not sure. How would look the surrounding circuitry of the 'cripple cap'? The circuitry board design is completly different from the original tomy- design.

Does anyone have experiences finding the correct setting of the receiver's adjustable coil?

best regards

Niquan

Edited by Niquan

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