Repair R/C Car Reciever

What happens if the transmitter is switched off?

The car will totally stop twitching. So, I thougt it could be transmitter that was bad, but I tried with 3 different transmitter and still the same... Looks as if the receiver has problem treating the incoming signal?

Looks like it is having problems round the detector / decoder areas. You probably need more then a DMM to fix this.

How should I go about to start troubleshooting? And what kind of test tool I would need?

What type of receiver is it? Regen, single or dual conversion?

Don

Without a service manual, I would need an oscilloscope with an RF probe for starters.

Hi Don, I wish I can answer your question. All I know is this is a 27 Mhz AM receiver for R/C car. Do you think it will be too much for a beginer to fix? I mean the circuit looks pretty simple, so I figured I want to give it try.

If the receiver does NOT have a crystal, it is probably a regen receiver and you might be able to retune it to the transmitter. If there is no crystal, look over the receiver to see if it has small adjustable capacitors and/or coils that have a slug inside that can be adjusted. You will need plastic tools to make any adjustments. Let me know what you find.

If the receiver has a crystal, be sure it is seated in its holder.

If it is not a regen, then it needs tools such as a scope and signal generator in the hands of someone who can trouble shoot without having a schematic.

Post the name of the city where you live and maybe someone will volunteer to help.

Don

On 18 Dec 2006 14:32:50 -0800, snipped-for-privacy@hotmail.com put finger to keyboard and composed:

This makes no sense. AFAIK the transmitter should not transmit anything until you move the joystick, otherwise its 9V (?) battery would quickly go flat.

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.

Hugh, It is one of those ESC receiver combo for micro size R/C car. May I ask you how much it would be to fix?

Franc, the transmitter for radio control car would start transmitting immediately after you turned on, that's why it is a MUST for hobbist to switch on transmitter before turning on the car.

On 19 Dec 2006 07:40:57 -0800, snipped-for-privacy@hotmail.com put finger to keyboard and composed:

I've repaired quite a few toy R/C cars and don't recall ever encountering one where the transmitter would transmit continuously without user action. In fact some remotes had no on/off switch. Maybe your hobbyist vehicles behave differently, but it still begs the question, what is it that the transmitter is transmitting? I can understand it signalling forward/reverse/left/right/turbo, but why would it signal a "do nothing" command?

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.

I would think the hobby grade transmitter are quite different than the toy grade RC. With the hobby grade transmitter, they are not only with

4 signal, but are propportional. So, there are steer trim and throttle trim noob/button so that you adjust the car's alignment or throttle at its neutral position. So, it is also dangerous for nitro or high power electric car to switch on the power on the car first before the transmitter is on. I don't exactly know how things work, but I think the transmitter should be on to keep the car in neutral position before applying throttle or steering.

But back to my very desperate question [I have no car to play for almost two weeks now :-( ], I have heard from other hobbyists mentioned when they have the powered on transmitter antenna accidentally touch the antenna would fry the car's receiver; and I have heard they fix the receiver by replace an inductor. I guess the inductor on the circuit board usually begin with "L"? Do you think I can check if the inductors are blown without investing with a probe or occiloscope by using just a DMM?

Are you certain the transmitter and receiver are on the same frequency?

From what I remember when I was a boy flying R/C planes (back in the late

70's), switching on the transmitter first keeps the servos from getting "jammed" at the far end of their travel, possibly damaging the gears. Whether this was a myth or not, or whether the current crop of RC stuff is subject to this...?

FWIW, I have seen them lurch suddenly in one direction when turning on the transmitter after the receiver. (I just HAD to try it :)

On 20 Dec 2006 17:55:30 -0800, snipped-for-privacy@hotmail.com put finger to keyboard and composed:

A simple DMM will only tell you if the inductor is open circuit. It cannot distinguish between a good inductor and one with shorted turns.

- Franc Zabkar

--
Please remove one 'i' from my address when replying by email.