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-   -   Black and Decker 40V Lithium weed trimmer PCB board damage (https://www.badcaps.net/forum/showthread.php?t=98007)

braxton 08-10-2021 08:56 AM

Black and Decker 40V Lithium weed trimmer PCB board damage
 
5 Attachment(s)
I have a Dewalt / Black and Decker 40V trimmer model LST136 Type-1.

It stopped working. Trimmer motor tests fine. I opened it up to find that the controller board had a blown component at position Q5. It also looks like a similar component at D6 has a bulging area. These two mosfets? are attached to a heat sink. The D6 component looks to be a MBR20100CTP rectifier. The Q5 component blew apart, so its difficult to read the label. I am hoping to get help identifying the Q5 component. Pictures are attached.

In the photos, the heatsink and the Q5 component have already been removed from the board. One of the three legs broke off of the Q5 component.
The last 2 pics are of the component I need help identifying.

stj 08-10-2021 09:11 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
100v is too low for a schottky diode - 250v atleast.
ideally 10x the running voltage!

braxton 08-10-2021 09:17 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
2 Attachment(s)
Quote:

Originally Posted by stj (Post 1063784)
100v is too low for a schottky diode - 250v atleast.
ideally 10x the running voltage!

Thanks. I will keep that in mind when ordering the D6 component.
Any idea what Q5 is?

I am attaching two more photos of the board

sam_sam_sam 08-10-2021 05:03 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Be careful with protection boards when repairing them make sure that the battery are not fully charged if necessary run them down to 3.2 volt and be ready to remove it from the tool or the charger if something goes horrible wrong

I have repair Ryobi battery packs sometimes you can repair them sometimes not

SluggerB 08-12-2021 06:59 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Quote:

Originally Posted by braxton (Post 1063789)
Thanks. I will keep that in mind when ordering the D6 component.
Any idea what Q5 is?

I am attaching two more photos of the board


Try and find someone who owns one (or buy a new one), open it up, identify the part, and then return it?

sam_sam_sam 08-12-2021 08:13 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
I just noticed that this battery pack is 40 volts which I do not have

Just be aware of this if this is an older battery pack the controller board of a new one might not be the same as one you have

braxton 08-12-2021 08:51 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
2 Attachment(s)
Here are photos of the trimmer with the model number.
The board is from inside the handle part.

The board is not from the battery itself.

braxton 08-12-2021 09:46 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Based on a closer look at the blown chip, it looks like it is an Infineon IRL3705Z mosfet.
Digikey lists it as obsolete.

Can anyone help out finding this part or an equivalent?
Thanks.

R_J 08-12-2021 11:12 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Quote:

Originally Posted by braxton (Post 1064229)
Based on a closer look at the blown chip, it looks like it is an Infineon IRL3705Z mosfet.
Digikey lists it as obsolete.

Can anyone help out finding this part or an equivalent?
Thanks.

If that is the correct mosfet...
Digikey IRL3705ZPBF-ND direct replacement, in stock

braxton 08-12-2021 02:21 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Quote:

Originally Posted by R_J (Post 1064237)
If that is the correct mosfet...
Digikey IRL3705ZPBF-ND direct replacement, in stock

Thanks!
Ordered a few of those and the MBR20200CTP (200V instead of 100V)

Hopefully that will get the trimmer working again...

R_J 08-12-2021 03:03 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Check the gate drive circuit resistor (R24) to make sure it is not open, When the mosfet shorted, many times it also takes out the drive ic, that sot23-5, best to get it's number before it is also unreadable.

sam_sam_sam 08-12-2021 05:19 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
This means that the charger has the protection board and the battery has no protection board might not even have a protection fuse in it

When you test this board be careful and be ready to disconnect the battery very quickly if something goes horrible wrong

braxton 08-12-2021 09:35 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Quote:

Originally Posted by R_J (Post 1064271)
Check the gate drive circuit resistor (R24) to make sure it is not open, When the mosfet shorted, many times it also takes out the drive ic, that sot23-5, best to get it's number before it is also unreadable.


R24 resistor has 753 written on it and tests at 75.5 Kohm

braxton 08-12-2021 09:45 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
1 Attachment(s)
Quote:

Originally Posted by R_J (Post 1064271)
Check the gate drive circuit resistor (R24) to make sure it is not open, When the mosfet shorted, many times it also takes out the drive ic, that sot23-5, best to get it's number before it is also unreadable.

The sot23-5 chip is hard to read but it looks like GX3mD maybe?

braxton 08-13-2021 05:32 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
1 Attachment(s)
Replacing the 2 chips had no effect. Still dead.
What about this component (largest chip in the corner) in the attached photo?

stj 08-13-2021 08:15 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
the "dale" part is a resistor - it should look like a short circuit.
clean the board with alcahol - it's hard to see the parts clearly.

R_J 08-13-2021 09:49 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
After a closer look R24 is likely the resistor between the mosfet source pin (Dale resistor) and the CS pin of the ic, and not the gate drive resistor. Check that the resistors between the gate and the ic are ok.

braxton 08-14-2021 09:06 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
3 Attachment(s)
Quote:

Originally Posted by R_J (Post 1064516)
After a closer look R24 is likely the resistor between the mosfet source pin (Dale resistor) and the CS pin of the ic, and not the gate drive resistor. Check that the resistors between the gate and the ic are ok.

I tried to take better photos of the board.
I also measured all of the resistors on the board and all seem to give an ohms reading (Highest was 100K and none seem to be open as far as I can tell).

petehall347 08-14-2021 10:27 AM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
1 Attachment(s)
what about these solder joints ?

sam_sam_sam 08-14-2021 02:58 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Quote:

Originally Posted by petehall347 (Post 1064626)
what about these solder joints ?

I agree with you that these connections do not look very good

braxton 08-15-2021 12:12 PM

Re: Black and Decker 40V Lithium weed trimmer PCB board damage
 
Those contacts are soldered well on the opposite side of the board, and continuity from both sides of the board to the relevant connection points is good when tested with a multimeter.


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