SCX LIGHTS
 

From conversations on the forum, especially this thread, it was obvious that some of us were having problems with the lights on a couple of recent SCX cars - the Corvette C6R, Ferrari 360 and Aston Martin DBR9.

So a bunch of us put our heads together to try to figure out some solutions...

The problem seems to be that the light circuit in the SCX cars can't handle the higher voltage put out by some track systems, especially Scalextric. Components fail and the lights stop working. Only the front lights seem to be affected. 

Please Note: Not all SCX cars use the same lighting board, so this fix may not work (or be necessary) for all cars.

We needed two solutions - a way of repairing cars with damaged lights, and a way of preventing the lights being damaged on future purchases.

The photo below shows the 'preventative' measure. This only works for cars with undamaged lights. The positive feed to the light board has been cut and a 100 ohm resistor fitted instead. This limits the voltage and should be enough to protect the circuit board from damage. I say 'should' because although this has been tested and proven to work, we don't know how well it stands up as a long term fix.

(Thanks to Zipp for the pic.)

The second job was to try to fix the cars with damaged lights. The SCX board is very small and delicate, and replacing components on it is way beyond my level of soldering skill!

So with some advice (and maths!) regarding resistor values from RichG I did some experimenting.

I used some cheap LEDs from an eBay seller. They came with 470 ohm resistors. The calculated value was 495 ohms, so 470 was close enough.

These two photos show the simple light circuit fitted to the Vette and Aston. The resistor is fitted between the positive feed and the positive side of the first LED. The negative leg of the first LED is soldered to the positive of the second LED. The negative from the second LED is soldered to the negative feed. 

And it works! The lights come on from about 1/3 throttle and get progressively brighter.

But, as I found out with one of my cars, if you put the car on the track the wrong way, the lights go pop! So a bit more work was needed.

More advice from Rich lead to the installation of diodes to protect the circuits. The diode blocks the current if the car is put on the track the wrong way (you just have to make sure you install the diode the right way round!). The diodes also drop the voltage slightly, which should give the LEDs more of a safety margin. Despite the voltage drop the 470 ohm resistor is still the nearest suitable value.

I've fitted the diodes to all three of my cars, and between them they have covered somewhere in the region of 1,000 laps to date. The lights on all three still work perfectly. 

(the diode is arrowed in the pic below)

Although soldering such small components is quite fiddly, it's really only a few minutes' work. 

The total cost of the components mentioned (LEDs, resistor and diode) works out at less than £1 per car, so it's a cheap fix as well as a simple one.

There's also the potential for lighting other makes of cars too...

Thanks again to Rich and Kev, without your help I'd never have got these cars sorted.  

Have fun, and mind your fingers!
Taxi

We're looking forward to more articles    
in our SLAP My SlotCar Series.      

Stay tuned!