Milwaukee M12-18FC fast battery charger - blown TOP268EG?

[spleenharvester]

I bought 5 of these chargers as parts/not working from the same seller. Upon receipt all were dead and had blown or missing 3A fuses. Upon connecting to mains I find there is +330VDC across the filter cap and nothing past that point.

TOP268EG is visibly scorched on all 5 units, with the scorch mark being between drain and source pins. Is this a common fault or have these chargers all been killed simultaneously by a power surge?

Any ideas what else might be damaged? I am in the process of tracing a schematic for these parts

[CapLeaker]

Very common fault for these type of TOPxxx or LNKxxx switching devices to blow. Same on other battery chargers, washing machines, etc. Look like a T220 with 6 pins. Go to YouTube and search for "buy it fix it Milwaukee" He made a few videos on how to repair it. I have repaired a lot of devices with these type of switcher. Gotta be THE worst switcher ever designed on earth. Take some straight shot, high resolution pictures from top and bottom and upload them here using the attachment function. Most of the time it is the switcher and the fuse are blown, but depending on how the circuit is designed more can be blown too.

[spleenharvester]

Ah yes just found a video with exactly the same fault. Unlike theirs fortunately it seems like none of my 5 have damage to the surrounding components, nothing short/open, diodes test OK. Internal fuses are all OK, it was just the plug fuse blown. Four out of the five units had one or more pads lifted when removing TOP268EG... fortunately it looks like an easy enough jumper repair.

I'm working on a schematic for both M12-18FC and M12-18C at the moment anyway, will upload them at a later date

[stj]

when you see a TOPswitch device, replace the startup capacitor allways.
i have fixed dozens of settop boxes with topswitches, if the cap dries out they go into a startup loop like a rythmic pulsing - then they go bang!

[CapLeaker]

Whatever you do around that TOPxxx or LNKxxx that area too and bottom needs to be squeaky, hospital grade clean. Otherwise it may blow shortly after again. Happened to me before.
Looks like some oxidized solder problems? A not enough heat and or B didn't use flux and added 60/40 leaded solder first before desoldering.
Yes, these TOPxxx switches can fail like that and just take the fuse with them, nothing else.

[lotas]

It happens that they take away the feedback optocoupler...

[spleenharvester]

Replaced the TOP on the first unit today, worked straight away. My plan is to put jumper wire on every pad as I don't trust even the intact ones not to crack in the future.

Looks messy as hell though. I used 22AWG solid core wire. Will this hold or does it need more cleaning up? Also attached the relevant section of the work in progress schematic

I am going to reapply conformal coating once it is done too

[CapLeaker]

Replaced the TOP on the first unit today, worked straight away. My plan is to put jumper wire on every pad as I don't trust even the intact ones not to crack in the future.

Looks messy as hell though. I used 22AWG solid core wire. Will this hold or does it need more cleaning up? Also attached the relevant section of the work in progress schematic

I am going to reapply conformal coating once it is done too

Just make sure this is hospital grade clean on top and bottom between the pins. Otherwise you may be changing it soon again. No speck of dirt, lint or whatever. Good job! These TOPxxx, LNKxxx, TNYxxx are very well known to raise havoc. Most of the time if I find such a switcher and the unit is dead, all it needs is the switcher to be replaced.

[spleenharvester]

Cheers CapLeaker!

Did the second one today, here it is after a fresh coating of Ambersil. This one was more of a nuisance as all the pads were shot. Still looks quite messy but probably as best as my shaky hands can do. It initially didn't work because the 10K resistor was open, I'm not sure if it was blown with the initial fault or if I overheated it but it works fine after replacement.

3 more to go

[CapLeaker]

Keep em coming! I wanna the the other 3 repaired.

[spleenharvester]

I've gotten 3.5/5 repaired now. First 3 worked just fine. Fourth one, I knocked a resistor off and accidentally replaced it with a 10ohm instead of a 10kohm and it never worked again, I think I am just going to scrap that one. The fourth one though, M12 slot works fine but M18 flashes green/red on any battery that is perfectly fine on another charger. Anyone run into this before?

[spleenharvester]

So I determined the RS6334 op amp was dead. Replaced it, the M18 battery began charging... then a few seconds later the whole board went completely dead. No VCC. I think the TOP IC has blown again. I can't be arsed with it anymore so it's going in the bin. 😁

[CapLeaker]

I've gotten 3.5/5 repaired now. First 3 worked just fine. Fourth one, I knocked a resistor off and accidentally replaced it with a 10ohm instead of a 10kohm and it never worked again, I think I am just going to scrap that one. The fourth one though, M12 slot works fine but M18 flashes green/red on any battery that is perfectly fine on another charger. Anyone run into this before?

Number 4 charger where you knocked off that 10k resistor R6? That’s the current adjustment pin of the Topswitch.