Have a look at the detector : it will be mounted pointing art the spindle under the gear cover. Photo is of my WM280, but yours should be similar. Black wire at top connected to sensor on the L bracket: my sensor has a red LED, but I don't think that's universal.

Potential faults: sensor loose on bracket, misaligned, not close enough to the magnets on the spindle, or plastered in grease. Maybe the magnets have come off – unlikely.

The other easy-fix possibility is at the other end of the cable where it plugs into the tachometer circuit behind the front-panel : it may have come loose in transit. Make sure the plug is inserted properly.

If it's not obvious and a new lathe speak to the supplier.

Dave

It may also be a disc reading type that is mounted inside the head between the two bearings and accessed by removing the front cover which is what my Warco 280 has.

Whoops, I didn't read the exam question properly! If the display is completely dead check the power plugs, sockets and wiring rather than the sensor. Mine is fed low voltage from a regulator on the mains filter board. It's fairly obvious how it works – follow the wires and make sure they're OK at both ends.

While Chinese Hobby lathes aren't as badly made as some believe, they certainly aren't perfect either! Mildly slapdash assembly results in minor faults. A plug not pushed fully home might come loose in transit, and this is made more likely because some wiring is able to flop around rather than everything being rigidly secured in a loom. Untidy rather than dangerous in my experience, but a flapping wire might be enough to dislodge a connector when the machine is transported. The flicker suggests power is nearly getting through, could well be a loose connection.

Dave