COLCHESTER BANTAM PROBLEM

Yeah, but no.

The original switch melted and kept popping you overloads and now a new one does the same. Surprised your Sparky didn't put a clamp meter on it to check the current draw though if he only fitted new equipment he might not expect it.

Frankly this screams motor field coil fault as a next thing to check for.

It doesn't necessarily suggest a field coil fault Dave.

My switch melted as oil got in it, causing arcing which melted parts of it and causing it to short. This could be the same problem. The new switch 'either does nothing or trips the overloads' depending on how it's wired up. It needs to be wired up correctly! It it's connected incorrectly then it is likely to either not work or trip something depending what is connected to what. 1st thing MUST be to ensure that the new switch is making the correct connections in the various positions. Unless you've got that it will never work. Once wired correctly if still not working then yes check the motor. The motor could be checked 1st but it still won't work unless the switch works correctly.

If the switch itself isn't available, is there a technical description of it? Might be able to crack the problem by comparing it with the technical description of the proposed replacement.

I agree with others: a fix requires the circuit to be understood well enough to remake the connections correctly. Guessing is unlikely to get there because there are a multitude of wrong answers, some of which might damage the switch on the way.

Also possible the old switch isn't the root cause, it could be the victim of a motor or other electrical fault. This can only be investigated when the replacement switch is known to be wired correctly, and the machine still doesn't work. Be good if oil dripping on the switch was confirmed, otherwise there may be more trouble ahead.

Don't panic - take it logically step by step.

Dave

Edited By SillyOldDuffer on 10/01/2022 13:34:32

Little bit of progress today, we checked the motor and it runs fine. My sparky brought with him a cardboard box full of electrical "things" So after a bit of deliberation, we set about removing all the old wiring (carefully noting where everything went and marking accordingly) . He then mounted a din rail, and started to populate it with all the appropriate "things" to make the lathe a bit more modern.

After about 4 hours work we were ready to give it a try, and even though all the electrics were on top of a bucket outside the lathe, I switched it on and hey presto !! it runs great, forward/reverse - - twin speed on the motor - - even have it running using a generic rotary switch connected to the apron lever. So today I am a lot happier. We don't have the coolant pump sorted out yet but my sparky says he can't see a problem there.