IP Pot and Chip

[Hope Mountain Railway]

Can anyone tell me whether it is possible to check the Pot and Chip of an IP Speed controller with a meter? I've got an 8 AA 1000mAh pack and an Essel Chassis with RS 385 motor. Its run quite well for a while, but suddenly failed the other day whilst turning the wheels slowly to reveal the Wheel Gauge changing grub screws. All switch wiring appears OK and the chassis works fine when connected directly to the battery. I can't make out the number on the IC to try and order one. Any help or advice appreciated. Thanks

[Big Jim]

Can't help with testing the chip but a multimeter connected to the potentiometer should be able to check that the resistance changed across the range.
Try contacting Ivor at IP to see if he can tell you what the chip is.

[sstjc]

I'm not familar with whats on the IP board but its unlikely to be the pot which is faulty as its most likely wirewound which means if it is overloaded its will most likely just heat up rather than fail. The most likely fault, if there are no other components on the board, is with the chip. If you replace it and it is soldered in make sure you use a crocodile clip or similar to act as a heatsink so you don't fry the new chip.

Barry

[GTB]

Can anyone tell me whether it is possible to check the Pot and Chip of an IP Speed controller with a meter?

I build my own, so no direct experience with the IP controller, but looking at the pic on the IP website the potentiometer is a standard 16mm carbon potentiometer. They do wear out, but usually develop dead spots before they die completely.

The pot. will have the resistance printed on it somewhere, it may be in the form B1k (the number may be different). B means a linear taper, the number and the k is the resistance value.

Easy enough to check if it is working, just set the DVM to volts and make sure the voltage between the centre terminal and one of the outer terminals varies as you turn the knob. Or disconnect it and check that the resistance between the central and each outer terminal changes smoothly as the knob is turned. If it's worn the resistance will go very high at one or more positions. If it's fried, it will be open circuit.

The IP circuit is very simple, so the 'chip' is probably a darlington transistor and the package type shown on the website suggests it could be a BD681, or equivalent. Again it will be printed on it somewhere, but it can be very small and faint, so use a magnifier and good lighting.......

If the pot. output voltage is varying OK and the voltage across the motor remains at zero, the transistor is dead.

Both the pot. and the transistor are standard parts and should be easily available over the counter at somewhere like Maplins, etc.

Regards,
Graeme