Do you have a multimeter to test out voltages and circuits?

Shame about the low resolution on that wiring diagram 🙁

MichaelG.

.

Sorry, yes. The fuse will be on the lathe somewhere.

Do you have a lab type power supply? You could try putting say 30vdc directly to the mill head to see if it spins. At least you would then know if the motor is kaput.

Not sure tbh. You probably need to be a bit closer to the motor specs. You may risk burning it out.

Does the motor have a plate or sticker on it showing the specs?

I know there is a sticker on the mill head but that is deceptive, because it shows the voltage and amps to the lathe, not the mill head motor. (I had this exact lathe/mill setup and also had problems).

A lab power supply is safer because most of them have multiple protection features.

The circuit doesn’t show how power gets to the motors so I’ve added them, red + and blue – :

• Power comes out of terminals 1 and 2 on the AP Board
• DC + and – pass via reversing switch (P1 P4) to SA1
• SA1, has 3 switches, of which two (10, 11) are used to power either the lathe or the mill.  The circuit is very simple – mot much to go wrong.
• There are no fuses or safety cutouts between the power supply and motors.

Testing requires a multimeter.  Buy one, cheap will do, anything with a 200V-ish DC range.

Power On, if the lathe turns, the power supply is good and the fault lies elsewhere.

• The fuses must be OK, and, power must be reaching connectors 10 and 11 on switch SA1, and from there to the lathe motor. Otherwise the lathe wouldn’t turn.  Set speed to low, but ensure the motor spins.
• With the mill unplugged, set switch SA1 to the mill position (lathe should stop), and carefully probe the pins on the socket with the multimeter set to 200VDC or more.
  • If needle moves then power is reaching the socket.   Therefore SA2 and the wiring to the socket is good.
  • No needle movement means SA1 is faulty, or a connection broken, or the socket is fault.  Check for power on the socket terminals with the multimeter.  Look for loose connections etc.
• If power is available at the socket pins, gets more difficult.  Plug the mill in:
  • Probe the motor to see if power is reaching it. If it is, the motor is the problem. Check brushes.
  • If not, something wrong between socket and motor
    • the plug and socket may be a poor fit.   Depends on the design and how well made they are.  Might be as simple as splaying a split pin with a screwdriver so it makes contact.  Or cleaning corrosion.   Otherwise, replace both.
    • As the mill head is plugged in and out, the cable may have broken inside the plug, or less likely, fractured inside somewhere along the cable.   Replace plug and cable.

If the plug and socket are hard to find, there’s nothing special about them.  Any plug and socket that takes 200vdc will do.

Comment:  these mill-heads often fail, implying a design fault.  The motor, cable and plug are simple – nothing complicated in the head, so it should “just work”.  My guess is the plug and socket don’t stand-up to being plugged in and out or dislike vibration.  Not quite fit for purpose.

As usual, grateful if others review what I’ve suggested:  I may have missed something or misunderstood the circuit.

Good luck.

Dave