Router speed control electronics

[robgraham]

My 1200W router is not functioning properly. If it wasn't that they look perfectly OK I would say that it was brush problem ie erratic power, so I'm going to have to come back down the chain. Switch is OK so it's something else; I'm going to assume it's the electronics in between that is guilty.

The box has discrete components so I'm may be able to find what might be no more than a dry joint, but it would help if I didn't have to reverse engineer the circuit Does anybody have a reference to a typical universal motor speed control circuit? Is it likely to be phase or PWM control ?

Thanks Rob

[John Rumm]

IME the most likely cause is a fracture in the cable. Check that carefully first before looking for more sinister faults.

You could eliminate the dry joint possibility by simply reflowing all of the joints. I doubt there are that many components in there!

I would have thought the latter.

[robgraham]

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Just in case anyone searches on this topic, the fault was a broken wire to the speed control pot. I didn't pursue the control electronics but did come to the conclusion it was just phase control - googling found that STMicroelectronics had a suitable application note on the subject

Rob.