Radio Control Problem

[Andrew Smith]

Hi,

I have acquired a steam engine with a SPEKTRUM DX4e radio control unit (pic attached). Yesterday it suddenly opened the regulator to full and wouldn't shut it off or respond to any commands. Fortunately there was no serious damage to the engine, but I'm anxious about using it again. Any ideas what might have caused this and how to fix it?

Thanks

Andrew

 

[PhilP]

This might be why it was sold, perhaps?

The horizontal trim control on the right stick is fully to one end of its travel, but I doubt this would cause it.

Low transmitter battery, perhaps?
The channel reverse switches could be corroded/dirty? - Try 'wanging' (technical term) them back and forth a few times..

You can power this up without steam, so fairly safe to fiddle with.

PhilP

 

[dunnyrail]

You could put the loco on a pair of wooden blocks under the buffer beams (wheels clear of bench) to test it out in live steam to see how it reacts to changes/faffing around with no fears of the engine running away to damage itself.

 

[PhilP]

Another thought:

Check for chaffed/melted/trapped servo wiring on the loco..

PhilP

 

[Paul M]

Never had or seen that before. As PhilP says it could be a stuck servo, or even a loose servo rod. Best to tryy operating it without firing up the engine, again as PhilP suggests

 

[3 minutes of fame]

Dodgy servo I would suggest. The position of the servo is controlled via a variable resistor (pot) inside the servo, and eventually these can fail. The same is also true for the operating levers on the radio control. The pot can become noisy or one legged, and send the full scale signal to the servo.

If you replace the servo, get one with metal gears. They have higher torque, less backlash and the additional metal keeps them slightly cooler.

 

[Fred2179G]

You don't need to steam it to check the rc operation. Turn it all on while the loco is cold and confirm the servos move the levers appropriately. In most cases, a servo goes to the middle position when the rx power is turned on, so try turning on the loco rx power first and watch the throttle.

 

[JimmyB]

In most cases, a servo goes to the middle position when the rx power is turned on, so try turning on the loco rx power first and watch the throttle.

The servo goes to the appropriate position according to the Tx, my RH fowler has3 servos, and dependant on where the control is is where the servo goes, because you ALWAYS switch the Tx on before the Rx.

 

[Fred2179G]

ALWAYS switch the Tx on before the Rx

Not if you want to see what the servo does when it loses connection to the TX.
I did say test this while not in steam!

 

[3 minutes of fame]

Not if you want to see what the servo does when it loses connection to the TX.
I did say test this while not in steam!

It depends if the receiver has a failsafe mode. Those designed for model aircraft may have a programmable setting, but this is less common with r/c cars and more general systems.

My basic £40 systems do not apply any motion to the servos until a valid signal is received, and then return to the neutral point if signal is lost. Some systems will hold the servo position if signal is lost, so it's trial and error to see what your system does.

 

[JimmyB]

It depends if the receiver has a failsafe mode. Those designed for model aircraft may have a programmable setting, but this is less common with r/c cars and more general systems.

My basic £40 systems do not apply any motion to the servos until a valid signal is received, and then return to the neutral point if signal is lost. Some systems will hold the servo position if signal is lost, so it's trial and error to see what your system does.

On my RH the "fail-safe" for the regulator is off/mimimum, but for the direction control it is the centre position.