Bosch 10V charger repair

[acertech]

Hello all of you!
I have a question about a IC that sits in a Charger to a Bosch PSR 10,8 LI-2 cordless drill. In the charger there are two IC from STMicroelectronics. One of them are ok since I read that it is a LM324AN but the other have the name "07502233" and I can not find it anywere. I have sendt a question to STMicroelectronics but I do not have a hope for an answer. Any know of this problem. If I want to repair this charger I do need specs on all components and this IC are the only one that nobody know about. I do belive it's made special for Bosch and beleve that the newer tell what it does in this charger. Hope somebody have a clue. Have a picture of it added.

[Andreas]

Hello,

looks like a custom made IC.
Could be also a microprocessor e.g. ST62T00.

With best regards

Andreas

[PTR_1275]

I've just opened my Bosch 10.8v charger, there is the LM324AN that you mentioned, the other chip is marked as follows

ML  07501952
1  G4214072
V6   G4   CHN

I had a quick look for data sheets, but couldn't find anything obvious. The only similarities between mine and yours is the 0750 in the first line and G4 in the second.

What is your charger doing / not doing (Other than not charging the battery)?

[KL27x]

If I want to repair this charger I do need specs on all components

Not by a long shot. Unless that's the part that is broken. You aren't trying to reverse engineer this charger, are you?

I had one of these chargers die. Model BC430 charger, anyway, if that's what you're talking about.

It worked once or twice. Then the third time I plugged it in, it went kaput, instantly. LEDs out. I assume a faulty design with inadequate input protection/MOV or whatnot. Anyhow, I don't remember how I troubleshot (tense?) it, but I don't think I even looked at a schematic. I am sure I checked for 10.8V output, and didn't get it. I probably googled the part numbers on the heatsinked parts to determine the main switching FET. And from there, I determined the switching controller and FET were bad (or maybe I guessed. Don't really remember; but I reckon I probed the output pin on the controller (/FET gate) and found high voltage). I ordered the parts (x2, in case something else caused these parts to break), subbed them out, and the charger has worked ever since. I don't know what any of the other parts do, and I never did. You want the charger to give you 10.8V... does it do that? Work back from there, concentrating on where the money is.

In my case, I suspected a blown FET due to how the charger died. My diagnosis is surge on plug-in, glitch in the controller resulting in a half/slow switch > instantly blown FET, which shorts the gate to the source > hi voltage to the controller output pin destroys controller. But if I had more than the first clue what I'm doing around a switching power supply, I'd have figured out a way to ensure that can't happen again. 

I saved this stuff to a project in my Mouser account, at the time. (Love Mouser for this... 5-6 years ago, and I still have it.)

FET: STP9NK50Z

Controller:  UC3842BNG 

It looks like I also ordered (or at least contemplated ordering) a replacement rectifier diode and a spare fuse. But I don't recall those being bad.

diode:STTH1602CT
fuse: 021501.6MXESPP

During a move, I lost one of my batteries. But the faulty charger was replaced under warranty. So I have two chargers and one battery. Go figure.

*If I recall correctly, it's the heatsinked TO-220 and the 8 pin chip front and center in Nowlan's first picture, below.

[nowlan]

Here are some horrible mobile photos of my US charger. Im curious why the big capacitor has brown tinge to it.
Rust or conformal coating?

[StefanPutureanu]

For anyone that still want to fix this type of charger (there are many chargers like this Bosh one)
If the charger is lighting the LED but doesn't charge the battery try to measure the two parallel resistors that are in series with the negative connector of the battery. They should measure 0.1 ohm together. If they are bad change them with a 2w 0.1 ohm resistor.
Charging current is measured on this two, and the ground of the mentioned IC is connected through this two resistors as well - here the reason why I've searched for this IC and landed on this forum.

Color code of this resistors in my Bosh charger: Black, Red, Red, Silver, Brown - labeled R24, R25 on AL1814CV model.
I have fixed two chargers with the same problem.