Hi I have a Makita li ion battery charger that doesn't work anymore. Plug it in and no LED's light up.

There is no sign of damage to any components, caps all look good, nothing looks burnt, checked all solder joints, all looks good.

I have tested the cord and fuse for continuity, all good there.

Could someone give me some ideas what might likely have failed and what possibly I should test and how?

I have limited knowledge of PCB's and components, I do know what caps are diodes, mosfets ,resistors etc, and I can test live with multi meter if need be.
(i know to discharge that big cap also)

If you need anymore pics of a certain area on the board I can upload as needed.

Thanks for any help.

 

Check the voltage across the large capacitor (photo marked) it should read around 300V DC, also check the transistor on the heatsink for shorts, check the thermistor for open circuit, and the fuse on the pcb.

This is a switch mode psu, so it rectifies the mains voltage to DC and pulses a transformer to produce low voltage on the output side .

 

Thanks for the reply Dave,

As I have little experience testing components on PCB's can you run me through the procedure of how I should go about testing the cap for about 300V DC first up??

Then we can move on to test the other components listed.

 

I have powered up the board and got 328V DC at cap,

Fuse is ok,

Not sure I done the thermistor right, measured 03.63 on ohms setting, warmed up a little went to 02.60,

Transistor, I measured in diode mode from middle to right side, 0.534 and OL reversed,

Let me know if I need to retest components in a different way.

Thanks.

 

Here is a pic of the transistor, which way should I be testing this?? I take it in diode mode?? but which leads to what terminals??

 

It's a MOSFET. Read the part number on the face of the transistor.

 

It's a N type Mosfet, you can measure across the D and S terminals for short on Diode function, but ideally you need to remove the D leg, it will read open circuit one way and 0.7V the other way.

 

Hi,
Post #4.
As I see, power cord, diode bridge, thermistor , RFI choke all are OK. Sounds like the power transistor is OK , too.
Check voltage on the pins of the capacitor CE3

 

Thanks Pyrex, cap at CE3 is 12.6 mv DC.
I take it that seems too low??

 

So the Mosfet isn't being pulsed , so no output, the main chip is U3 on the trackside, check voltage across Ce6, .
You can measure the voltage on the Mosfet D and G pins put Negative lead on TP8, and see what is on the D and G pins on AC and DC.

 

Thanks Pyrex, cap at CE3 is 12.6 mv DC.
I take it that seems too low??

No voltage on the CE3. As it was mentioned, power transistor isn't being pulsed. It seems , IC U3 do not work. You need the datasheet of the U3. It is in SMD style, so it only has a few symbols on it, so first you need to determine what type it is according to the smd symbol databook. For instance :

https://www.google.com/search?q=smd...7j0i22i30l9.6287j0j7&sourceid=chrome&ie=UTF-8

 

So I take it the IC at U3 is the cause of the problem and needs to be replaced??

Im not sure I follow the " it only has a few symbols on it "?? and im not sure what im looking for in the link you posted??

The numbers I can see on it are I think, OB2512NJP, well not sure on the "O" because it possibly looks like its been a bit hot at some point and can hardly see whats on it.

I think I found something that could possibly be it??

https://radiolux.com.ua/files/pdf/OB2512RN.pdf

 

No need to change anything. The faulty component must be found. It's hard to tell from the photo if the IC has seven or eight pins.
You need to find what controls the power transistor.
If possible, get a circuit diagram of the charger.

 

The IC has 7 pins, it has the same numbers on it as in the link I posted. OB2512NJP
https://radiolux.com.ua/files/pdf/OB2512RN.pdf

Charger is a DC18SD, not sure im going to be able to get a circuit diagram for this??

You need to find what controls the power transistor.

Im not sure where to go from here??

 

You can measure the voltage on the Mosfet D and G pins put Negative lead on TP8, and see what is on the D and G pins on AC and DC.

So do I measure TP8 from here??

 

check voltage across Ce6, .
You can measure the voltage on the Mosfet D and G pins put Negative lead on TP8, and see what is on the D and G pins on AC and DC.

D Pin - AC 137V - DC 333V

G Pin - AC 3.5 mV - DC 0.2 mV

Cap Ce6 - 335V DC

 

So the chip has got a DC supply, it looks like the Mosfet isn't being switched, so it could be the chip, any better picture of the chip, the one you mentioned has only 7 pins?

 

Yes its has 7 pins.

 

The IC has 7 pins, it has the same numbers on it as in the link I posted. OB2512NJP
https://radiolux.com.ua/files/pdf/OB2512RN.pdf

Charger is a DC18SD, not sure im going to be able to get a circuit diagram for this??


Im not sure where to go from here??

If it is not possible to obtain the circuit diagram, this complicates the situation a little bit, at least.

1.As I said, look at the IC datasheet.Datasheet is the main document, and can be followed if we do not have the circuit diagram. Found the transformer, it's tied to the "C" and "C" pins of the IC. Found the capacitor Co and measure the voltage on it.The voltage should be several volts, non-milivolts.
2.Take a sheet of paper and draw those components that are connected to the power transistor gate. This way you will understand how the pulsating voltage to the power mosfet gate is generated

 

Battery chargers want permission from the battery pack to turn on. That is from those extra contact pins telling a temperature signal, a voltage signature, an interlock, overdischarged condition, matching pack... whatever the manufacturer decided to implement.
If any means to try the battery in other charger, do it to check if same behavior. How long ago was that battery functional ? What voltage did you measure now ?