HI Chris
Not familiar with your particular charger but I have a similar Robbe offering. Looking at the Graupner web site the MultiLader 3 appears to have three output connectors, a standard radio set plug, a transmitter plug and a Nimh battery plug. From your description it would appear that each plug has a separate output and works one of the LEDS when a battery is connected. I agree with Gregg re the circuit board or component failure. its possible that a recent (faulty) battery charge resulted in some overloading and if you are lucky(?) the evidence will be clear to see. I found my problem that way. Regretably the circuit board was very fine tracks and the components surface mount so I lost one of my chanells, but managed to restore the rest by isolating the damaged circuit. You may need a good eyesight or a strong magnifier. Good luck. 😀

Anything is worth a try, afterall there's nothing to loose. the price and easy availability of replacement electronic components from places like "Maplins", you could have a nice repair business in repairing battery chargers, once you crack this one, Best of luck !

I used to be 'in to electronics' but stopped around the time red spot transistors arrived! however you have given me the incentive to open it up and have a look at what might be wrong. Thanks
Chris

Sounds like a fault on the circuit board, a diode or resistor has failed. Unless you are "in" to electronics and can check all the seperate items, its the only way of finding out what has failed.