Amadeal VM25L Uneven Motor Brush Wear

[noel shelleyParticipant @noelshelley55608]

Richard where abouts are you ? Noel.

[MacolmParticipant @macolm]

For such circumstances I keep an old security light with high wattage mains halogen lamps, for example 1000 watt. With the mains supplied to the circuit under test via this, a dead short merely makes the lamp shine at full brightness. Something like a electric drill motor running on light load will scarcely light it, and the voltage dropped will be small. From cold to full brightness, the resistance of a halogen lamp increases by more than ten times, so a cold 1000 watt lamp might be perhaps 5 ohms. Lamps could be connected in parallel, and will share the current well due to the rapid resistance rise with current.

Unfortunately such lamps are no longer available to purchase new, but almost certainly available second hand.

[Richard Kirkman 1Participant @richardkirkman1]

Hi Noel,

The mill is based in Darlington.

Hugh from Amadeal reached out and provided me with some testing instructions for a lathe with a similar circuit board. I found that the Speed controller seems to be the issue. I will order a new one and fit it in a few weeks.

Posting the testing as well for anyone else in the future.

COMPLETE CJ18 ELECTRONICS CHECK
We can check a couple of things first to see if we can diagnose the fault. Since the control box trips
the electrics (i.e. doesn’t blow a fuse), you can check to see if it is the motor, filter board or the
speed control board that is causing the issue. The speed control board is the large board in the
middle of the control box, that is mounted on an aluminium backing.
First it is best to check the motor. To do so, unplug it from the filter board (the small board at the
bottom that slides out). It will have a green or orange two pin connector into the filter board.
Between these, there should be between 3-13 ohms resistance. You can check multiple coils by
turning the motor by hand and letting the multimeter settle and hopefully should still read in in that
range. If you use a 9V battery or a DC power supply on these two wires, the motor should spin very
slowly (make sure you remove the belt to test this otherwise it will not turn very easily). Leave the
motor disconnected for the rest of the testing. Also, it is recommended to check the condition of the
motor brushes. If this is fine, we can check the filter board.

If you disconnect two wires into the speed control board, labelled L1 and L2 (both usually red), these
should be 240V AC between the two wires. Please be careful! This is effectively mains power so is a
very high voltage and can injure you. If that is fine, the filter board would seem to be functioning.
However, since you say it trips the fuses as soon as you switch on the machine, this test may not
work as it may be the filter board that has had issues.

You can check the speed control board by plugging L1 and L2 back in and then use the multimeter on
A+ and A- on the same board. These need to be on the spades, not the wires, so one way to check, is
to slide the multimeter tips into the plastic cover over the spades for these two. The voltage reading
for this will be DC with a minimum of 0V and maximum of about 230-280V. This range can be
checked by adjusting the potentiometer on the front of the control box. The output voltage will
increase and decrease with turning the potentiometer up and down respectively.
If you find the filter board does not respond correctly, you can still test the speed control board. You
can plug live and neutral directly into L1 and L2 (respectively), after removing the L1 and L2 cables
from the filter board. Then check A+ and A- as I have mentioned in the previous paragraph. Please
note, doing this bypasses the switches and fuse on the control board, so it may trip your circuit
breakers. You can still increase and decrease the voltage output using the potentiometer on the
front.

When testing the filter and speed control board, it uses mains power, so please be careful! If you are
unsure, stop and please let me know! If you could test for any of these and get back to us, I will be
able to advise what to do next. I hope we can diagnose the issues with this!

SPEED CONTROL BOARD CHECK
Another test would be to check the speed control board as this will determine if the motor is actually
receiving the voltage it needs. If you unplug the motor and two wires on the speed control board
(this board is the one with many wires connected with spade connectors and is on an aluminium
backing) which plug into A+ and A-. The wires are usually black, but this is not always the case. Use
your multimeter on the 600V DC setting (or similar voltage above 200V) on the two spade on the
board to test the voltage. Please be very careful with the high voltages to not short circuit or touch
anything with the main power on. Then switch the machine on as if you were to operate it and turn
the potentiometer (the dial on the front) up. When off, the voltage should be 0V, when on max it
should be around 200-280V and should increase linearly between the two points. If you could do this
test for us, we can determine if the electronics are working or faulty.

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