Milwaukee M12 M18 charger repair

[BigPete]

Thought to post up a repair I recently did on two of these chargers.
After replacing U1, TOP256EN, which seems to be a common failure and one I've done multiple times, these two ICs blew again, not instantly, but upon removing and reinserting the battery.
What I found was the snubber circuit had failed.
So after replacing U1 again, along with a resistor, polyester cap and a diode, all was well.
The parts and locations:
Replaced U1 - TOP256EN
Replaced D2 - 600V 1A Diode
Replaced C5 - 630V 4.7nF Polyester Cap
Replaced R12 - 68khm 2W resistor

Hopefully someone finds this info useful.

[sam_sam_sam]

Re: Milwaukee M12 M18 charger repair

“O” crap I have several of these chargers what wil be next to take a shit
How old are these chargers ?

Thanks for sharing your repair on these chargers

[BigPete]

Re: Milwaukee M12 M18 charger repair

They were older models going by the dust in them.
They regularly come up on the local buy and sell sites. All the ones I've repaired have had the U1 chip fail, except for one, which was a faulty plug, and I ended up replacing the U1 IC first thinking it was that.
It could be a similar issue similar to the C4 cap in Yamaha amps.
On these two chargers, the cap was out of spec and the resistor open. I replaced the Diode just to be safe.
It'll be just another thing to check.

[sam_sam_sam]

Re: Milwaukee M12 M18 charger repair

I am having an issue with one of my M18 volt batteries it is flashing all 4 fuel gauge light at the same exact time randomly and unpredictable times

I am not sure exactly what going on with this error I know what it means when the M12 battery pack does this is because the battery voltages are not balanced anymore and the battery pack has come to the end of it life and I suspect that might be the case with this battery pack as well but I will not have time to investigate this issue until next weekend

Sometimes when the M12 tool does this it because the fuel gauge meter is having some type of issue because when you put the same battery in another M12 tool it does not do the same thing because I have one M12 tool that flashes all four LED most of the time when you first put in the battery pack

[faraday28]

Re: Milwaukee M12 M18 charger repair

Check output diode, Optocoupler and cap beside the transformer.

If the transistor blow up, could be several factor including Output diode shorted.

If snubber goes blow up, maybe the optocoupler failed to make main transistor turn off so the energy goes to snubber, or the cap for "balancing" the transformer worn out (look at C10 and their friend) the cap usually use high voltage rating 1KV or 2KV or use safety Y Cap.