TOPIC:

Tamiya virgin technical help required.

I have just bought my first RC car, a 2010 re-release Sand Scorcher from eBay. The car is a fully built and I have run it a couple of times.

The car tends to have a mind of its own at times; overrunning when the throttle is off.

The car is fitted with an Acoms AR-2/27 receiver, AS 17 servo via a Techniplus AP-202 transmitter. It has a TEU-104BK speed controller.

I have read elsewhere that there can be communication incompatibilities with some Acoms kit. Does this system set up seem ok and what can I put the overrunning down to?

Welcome on TB.

I don't think your receiver can handle the 7.2V it is getting from the battery. Or is it powered separately by 4 AAs?
Just to be sure - did you turn off the transmitter when it went haywire?
And... did you turn on the transmitter before anything else?
Do the transmitter and receiver look like they're from the same era - what kind of crystals are in it?
Generally 27MHz is most prone to signal interference...

Sorry for all the questions. Just trying to eliminate some factors.

I wrote:

Generally 27MHz is most prone to signal interference...

Could be a lot of things but tbh, every single time someone has issues likes this, it seems to be with a Tamiya ESC.

Scorcher66 wrote:

Tamiya virgin technical help required.

I have just bought my first RC car, a 2010 re-release Sand Scorcher from eBay. The car is a fully built and I have run it a couple of times.

The car tends to have a mind of its own at times; overrunning when the throttle is off.

The car is fitted with an Acoms AR-2/27 receiver, AS 17 servo via a Techniplus AP-202 transmitter. It has a TEU-104BK speed controller.

I have read elsewhere that there can be communication incompatibilities with some Acoms kit. Does this system set up seem ok and what can I put the overrunning down to?

Welcome on board


Any time I buy a new kit I buy from somewhere that will let me delete the Tamiya ESC & save 10 quid, then I also buy a 15-20 quid Mtroniks ESC instead ... maybe that tells you something about my view on Tamiya ESCs


That said, I'm still thinking your problem sounds more like interference....

It doesn't help that the Scorcher was designed back in the day where radios were a bit different - the receiver antenna wire was twice as long (so there were no problems with getting a decent "effective height", and the transmitters were 5x the power - so less problems with interference caused by and collected by the whippy antenna support & all that metal at the back of the car.

I'm not sure what you can do about it though, other than making sure the tip of the RX antenna is as high as possible & avoids as much metal & other wiring as possible, and that you have fresh alkaline batteries in the TX.

Are you using the car in a built up are where any number of things could be interfering with the signal? Does it behave any better if you use it in the badword end of nowhere?


If you can exclude the possibility of interference & poor range/reception, then substitution of the ESC is the next logical step, I guess.

Edou, thanks.

I did initially make the error of switching the receiver on before the transmitter. When I ran the car today I had resolved that school boy error. The car was about 15m from me and just kept going when I took the throttle off. But interestingly it settled down after that?

The crystals are TX Band 1. I have reinserted the crystal in the transmitter as this was not sitting as fully engaged as it is now, but I only did this after running the car today.

Hi Jonny,

I have noticed that the antenna wire is only about 1/3 the length of the antenna. It is routed out the rear of the car and cable tied to the rear frame and onto the antenna. There is no slack to allow me to get it higher. I could cut the ties and get an extra 20mm or so but am worried it might be damaged on the motor casing, although that seems to be the route shown in the instruction booklet?

I have been running it around a farm, mostly open areas of hard standing with lowish rise farm buildings. My brother brought his Scorcher down recently and he didn't seem to have any problems with signal, but his is an expert build.

The runaways I had (also on 27MHz) only settled down after catching up with the car and cutting the power.
So it's interesting your car did that on it's own...
Crystals that don't originally belong to the transmitter can also give glitches.
I could name other possible causes but I think your best bet will be to get some cheap 2.4GHz gear.
Shops like Hobbyking offer systems for next to nothing.
Much less at least than the cost of wrecking your Scorcher.



Still, I am not a fan of the Tamiya ESCs because they lack any failsafes.
The LRP or Robbe I have would simply cut the signal and make the car stop...

Edou, it's powered by the 7.2v battery.

Thanks Edou.

Sorry, never mind that. Looks like the receiver has a BEC (it cuts down the voltage).
It probably would have started smoking by now otherwise...