Hi Gerald,

Links to photos work for me.

Yes, just connect the motor to a 12v battery. Although the motor normally runs at 110vdc, it should turn slowly on a 12v battery. Disconnect the motor from the control board to do the test.

The control board can be tested by connecting a 240vac filament light bulb to the output. Any wattage will do. The bulb will light dimly, and its brightness should go up and down with the speed control. Filament bulbs are thin on the ground these days because they're being replaced by modern energy saving lamps which are no good this test. However, Oven Lamps are 240Vac filament.

Take care doing the test. Although the controller only outputs 110v it hurts! Keep away from the circuit board when mains is connected.

Another possibility: the potentiometers used to control speed are vulnerable to dirt and wear. The centre wiper disconnects from the resistive track and the controller stops working. Cure is to replace the pot, cost a few pounds.

A faulty pot normally develops over time with erratic speed control or dead spots as the knob is turned. If the lathe failed suddenly whilst working hard, most likely the control board failed, in which case confirm with the light bulb test.

The motors are fairly robust unless made too hot by overwork. Worth inspecting the brushes to see they're not worn out.

Dave

Gerald,

Have you examined the underside of the board for dry joints or burnt copper tracks?

A magnifying glass is a good aid.

Good luck, Bear..

The fuse should be in the LIVE connection. Puttting it in the neutral is unsafe for two reasons.
/1 Most importanly but not obvious, if the fuse fails or is removed, even without a fault, it leaves the machine "dead" but with ll the circuits up to the fuse still live and waiting to shock or electrocute someone investigating.

2/ it does not protect against a short to ground inside the machine. This means the internal wiring or components could overheat or catch fire as they may not be rated to take the (more than) 13A the plug fuse will supply.

You should re-wire the fuse to the positive supply. What brand is the machine? bought direct from China or UK seller?

Robert G8RPI.

Edited By Robert Atkinson 2 on 04/09/2020 08:29:07

To let ypou know the Chinese milling and lathe of this type actually wire the L and N the other way round on the milling machine here is the same (L on N terminal and N on the L Terminal) which actually matches the wiring diagram. I though the wring diagram was wrong until I check what was really connected, it will work and is supplied by the factory that way round. I assume that some had printed the PCB's wrongly, but instead of throwing them away, they just altered the diagram to match.

It works either way round because the input is an alternating current. In terms of electrical function there is no difference between Live and Neutral, because they operate as a pair. But don't do it!

The important difference is safety.

Electricity suppliers make the system safer by ensuring that one wire is earthed, rendering it Neutral, that is at the same potential as anyone on the ground who touches it. No shock.

The other wire remains 'Live' and is dangerous. It coming loose and touching the metal chassis would turn the equipment into a widow-maker, except all exterior metalwork should be connected to earth, which instantly blows the fuse.

Fusing the neutral wire stops electrical fires, but it doesn't disconnect the live side, so the equipment is still a shock hazard. It fails dangerous. Then Mr Innocent opens the box and pokes around inside, wrongly assuming that the equipment has failed safe, and it isn't. To be safe the fuse must be fitted to the live wire, not the neutral.

General rule is to always unplug electrical equipment before going inside. Don't trust fuses at all! If essential to debug a live circuit, assume the worst and take every precaution. A few electricians are killed every year despite their training. Even when you understand, it's easy to make a mistake.

Dave