Repairing a electric toothbrush - electronics help needed

[HawkEye244]

K, so there is some backstory to this. I followed a youtube tutorial of how to fix electric brushes and successfully removed and replaced a flat Ni-MH battery in another brush, and hey presto it came alive again. I tried the same with this brush, but it appears to be dead. I'm thinking this perhaps could have something to do with the motor. As you can see it is pretty rusted up. I'm thinking perhaps the inside has corroded up which is why it is no longer working.

Is it worth me unwelding the battery connections and removing the motor to test it? HOW do i test the motor to see if it's working?

How do I test the PCB to make sure everything is as it should be? It is a relatively small board. I've tested a few connetions with the multimeter and there is voltage in many places so I'm hoping there is no damage to the board.

As per the photo I have removed the charging coil at the base of the brush and the LCD display but this should not stop the unit from operating?

I can solvent weld. The only way I'm going to have a chance is if I stay goal orientated to fix this brush. Studying electronic engineering for hundreds of hours is not something I have the patience for.

 

[bernardgreen]

Almost certainly customozed integrated circuits. There is very little chance of getting any information about them. Hence unless you are totally dependent on this specific brush for living ( or you what a project to get your teeth into ) the best advice is buy a new one.

 

[HawkEye244]

When you say integrated bernard do you mean there is a circuit running through the board as well as on top and on bottom?

 

[bernardgreen]

The little bits of plastic with lots of silver legs are the integrated circuits ( chips ). So called because hundreds of transistors are integrated onto a single piece of silicon. ( or in the case of a computor chip 10's of millions of transistors integrated onto a few square milli-metres of silicon

 

[HawkEye244]

I still don't understand why this is automatically unfixable ?

 

[bernardgreen]

There is a chance that a good clean and dry of the PCB will restore it to working order. BUT if the contamination was conductive enough to create short circuits that stopped it working then there is a significant probability that

1) the short circuits will have over loaded the circuitry inside the integrated circuit amd caused damage inside.
2) copper tracks on the PCB will bave been etched away by the corrosive action of the contamination.

The blue tinge to the corrosion suggests that copper has been oxidised.

 

[HawkEye244]

How do I test for short circuits then ?

 

[mattylad]

Looks more like the motor has corrosion within it, possibly preventing and voltage getting onto its terminals etc.

Does the motor turn? can you turn that litlle cog to make it do so?
Can you check for voltage on the motor? can you apply a voltage to it to make it turn?

 

[HawkEye244]

Looks more like the motor has corrosion within it, possibly preventing and voltage getting onto its terminals etc.

Does the motor turn? can you turn that litlle cog to make it do so?
Can you check for voltage on the motor? can you apply a voltage to it to make it turn?

Thanks matty. The cog does turn. When testing for voltage the motor appears to be dead, no reading anywhere on the connections.

How would I apply a voltage to the motor ?

 

[mattylad]

First find out what voltage it should have, probably the battery voltage. Just take a lead from each battery terminal and attach them to the motor.
Having the ability to turn it off would help, so don't solder them onto the motor.

If it does not turn then basically your stuffed. IMO it would cost more to get a replacement motor than it would to replace the whole thing and as much as I am a Freegler\recycler this is possibly going a little too OTT as it looks rather manky.

 

[HawkEye244]

Thanks matty I'll get on this and report back. I think these motors are sold on ebay I guess it's finding the right one. More pressing issues at the moment with a dud printer.

 

[mattylad]

Try your local Freegle, Freecycle and Trashnothing groups for spares