On 8 April 2024 at 14:37 Michael Gilligan Said:

Thanks for any thoughts

Do you have continuity from the white terminal on the motor and both of the others? (Maybe a few tens or hundreds of ohms?)

If not, I suspect that the device marked ‘T.P.’ is a thermal fuse that has gone open circuit. (It will likely be in intimate contact with the motor windings somewhere – possibly buried.

I think that the main supply for the motor is supposed to be between white & gray. My **guess** is that the black may be something to do with a start or reversing circuit.

If it was a blown thermal fuse I wouldn’t expect it to run or hum. My shredder goes both ways, if Michael’s does then I suspect it’s like a Parvalux motor, where for one direction you apply volts to grey, for opposite to black. Capacitor is permanently in series with one or other winding. Quite why it needs all the electronics is another question entirely. If my guess is correct resistance grey/white and black/white will be equal.

Like Andy has already said, I think the TP is a thermal fuse buried some where inside the motor windings, which is normal on these type of gadgets and could be faulty. if you are able to lift one of the capacitor leads and test using an ohmmeter between White and Black, if all OK then the thermal fuse is sound. The capacitor can also be faulty, I see an 8 micro on the label, so one from a five foot fluorescent could be used as a substitute for testing purposes. Just be very careful with capacitors as good one will hold its charge for a long time, short out the terminals with an old screw driver.  in fact just for testing purposes almost any cap will be OK providing it of 400 working volts or better, definitely not an electrolytic. John

Hi Michael, Connecting the  mains to black and grey is NOt the corrrect way to check the motor. With the black grey and white wires from the motor NOT connected to the cirguit board connect one side of the mains (Say neutral.) to the white wire. Connect live to the black wire. The motor should rotate in one direction. Then transfer the live to the grey wire. the motor should then rotate in the other direction. (If it just hums then the capacitor is nost likely the cause of the problem.)

NOTE The capacitor must still be connected to the black and grey wires from the motor for this test.

Les.

I never knew shredders were that complicated.  Forward / Reverse, current overload check, check bin, auto check for something to do, and motor speed.  Looking at the circuit board, there must be over 80 electronic components there. I think the designer lost the plot or perhaps never had a plot to loose in the first place.

Back in the day, we had a larger office shredder which used to eat 4 part computer printouts with interleaved carbon paper. It failed one day after probably 10 years service. I had a look in the “control box” to find a couple of chocolate box connectors, a capacitor and a neon light and that was about it.  The failure was a microswitch that had dropped off as the screws had disappeared into the shreddings. New 6Ba screws and it continued its service for many more years.

Not always the “over-complicated electronics” that fails. Our shredder – “no more than 3 mins in 30 mins” – still has a working motor. Still has all the electronics in working order. Pity one of the gears in the gear train broke into three pieces…

Disconnect white, black and grey wires (the ones going to the motor and 8uF capacitor) from the PCB. Using a safe connecion method connect white wire to live 240V supply and either black or grey to neutral.
INSULATE the unused wire!
Apply power and motor should run one way. Changing the wire connected to neutral should run the other way.
Given your previous tests if it does not run like this the capacitor is faulty.
A 10uF capacitor will work OK but is not ideal.

The TP device marked on the motor IS a Thermal Protector. From your previous tests this does not appear have tripped.

Robert.

Let the experts confirm Here

This problem keeps coming up, is it possible to test capacitors by connecting in line light bulb across the mains? If so can someone suggest value for bulb?

The electronics will include the function to continue running the motor so as to clear shreds after paper is past the input sensing switch.