Repair of Dewalt dcb101 battery charger

[suppala]

My new Dewalt dcb101 battery charger got dead during charge, only on second time , I opened the cover ,but unable to take out the pc for check as it was stuck with adhesive near base of support clamp of charging terminals. Any help with correct procedure for taking out the same as as the PC is also secured with two clamps over the two square slots on one side and a overhang clamp on the other. Also a circuit diagram for this model would be helpful This is a 110 volt model and staying in India, I use it with an AC adapter. I am unable to use my drill , a reciprocating saw and a circular saw in absence of charger for battery.
suppala

 

[Harald Kapp]

As the charger is new, you should have warranty. Have the unit replaced under warranty. That's the best option.

 

[73's de Edd]

Warranty in small towns in India can be problematic.

If you get inside confirm if the units circuit board is marked as being of DELTA manufacture.
I believe that will hold true . . .also seems like they put a large blob of silicone blubber on the foil side of the board, just under the FWB diode unit which is mounted on a corner of a heat sink and is not too far from the units main LARGE black electrolyutic capacitor.

Slowly lifting up on the board from the opposite side where there is CN2 connector with its GREEN WHITE and BLUE wires might let the silicone slowly pull loose and away from the board.

You should find / see some of that same WHITE POOKIE on the toroids and EMI chokes on the top side of the PCB.

The YELLOW circle area is usually the area with a blob of the POOKIE placed underneath it.
If you have to slowly lever up the board, use a heavier wooden stick, so as to not damage the PCB bottoms foil.
Just as the unit is, you CAN see most of the top of the PCB as it is,look at the RED rectangular area for any burnt carbon film resistors.

Typical De Walt Charger :





73s de Edd

 

[suppala]

Thanks.. Is it possible to get a circuit diagram with component details ..........Uppala

 

[shrtrnd]

Dewalt likes to proprietize their information. (So you have to deal with only them for repair) Unless somebody has a bootleg copy, you won't find one.

 

[73's de Edd]

Do anyLEDS light up on the unit. to signify that the unit is partially powering up.
And measure the voltage on the unplugged battery to see what voltage is currently being read as compared to the voltage listed on the battery. May have a shorted cell.

 

[suppala]

The charger is totally dead, No led lights up. There was voltage present at charger terminal strips when the unit failed, probably from condenser , which got discharged over a time and no voltage appears at terminals now. May be the fuse is burnt. I can only check after taking out the pcb..... Uppala

 

[73's de Edd]

Sir suppala . . . . . . . .

We can work around your current restraints initially, as I have marked up the path of the 110VAC from the line cord over to the black rectangular full wave bridge rectifier. Its mounted on the alum heatsinks corner where the LARGER yellow circle is . The smaller yellow circle is where your chemical AC line fuse is.
Taking a DVM and placing it in AC mode and a range >>> 150VAC should then have you ready to locate the two
~ and ~ symbols at the center of the rectifier block at the PCB proper.
If plugged into AC 110V AC now, and monitoring for voltage presence at those two terminals you can then see if your fuse and that incoming power loop is being good .

If finding AC you can then switch metering to DC voltage and expect ~160-170VDC output of that bridge at its + and - markings at the PCB proper.




If in doubt you can further use my fuse test procedure . . . . ..



73s de Edd

 

[suppala]

Dear 73s Edd,
Thanks. I put back the cover on my charger and tried to recheck my findings. When I switch on the supply(110) volts, I could find 18,5 volts at the two charging terminals ,but the indicator does not light up and also when I connect the battery , it does not take charge, Next, I connected the battery positive and negative direct to charger positive and negative, after removing battery from charger . Lo, the battery takes the charge ! Is it safe to carry on this way . In view of these findings could you tell me if changing led or any of the related components would solve the problem.
s Uppala ,March 29 ,2017

 

[suppala]

Dear 73s Edd,
Thanks . Before attempting to take out and check pcb , I wanted to take a recheck . I put back cover on charger and connected to 110 volt supply. As before , yellow indicator lights do not show up However a voltage of 18.5 volts could be measured at the positive and negative terminals of charger,but when battery is connected , it does not take charge . I took out the battery and connected + ve and - ve terminals of battery with +ve and -ve terminals of charger and succeeded in charging the battery. Will it be safe to continue this way by switching off charger as soon as the indicator lights on battery show full charge ( with 3 yellow bands lighting up.
I s it possible that only led has filed or the connecting circuits as well.
s Uppala March 29, 2017.

 

[73's de Edd]

Sir suppala . . . . . . . .


That charger can be a real problem if one cell drops out or will not charge.


I took out the battery and connected + ve and - ve terminals of battery with +ve and -ve terminals of charger and succeeded in charging the battery.

If you are able to get access to both the battery connections and the chargers terminals see if you can use some jumper wires with clips to be able to insert a DVM IN SERIES with one of the supply lines to measure the actual charging current on the DC AMPS function of your meter.
Then you can see the charge level and ALSO see if it tapers down with charging time.

The next action I might want to know is the battery voltage under a load.

Do you know anyone else with either your battery or charger or BOTH to be able to compare the two units actions against each other ?
Their compared test results would be MOST beneficial to BOTH of you . . . . in the future.


73s de Edd

 

[suppala]

Dear 73Sde Edd ,
As I already noted in my earlier post, the charging is perfect ,with the battery taken out from charger
and battery and charger _ + terminals only thro' jumper wires omitting the central 3 terminals of charger, the charging is perfect and all 3 strips of battery charge indicator light up showing charge completion .My only problem now remains that led indicator lights on charger do not function and I cannot charge battery With battery placed connected on charger .It must have something to do with circuitry of middle 3 terminals of charger. Any help?

 

[73's de Edd]

Sir suppala . . . . . . . .

Your 3 middle terminals are related to isolated battery voltage sensing and feedback to the charger.

And somehow I still think that your battery voltage got so low on the pack that it was not responding.
Indeed . . . . . now that you have connected right across the charger output to the battery terminals you were able to get a full charge on the battery.

Why don't you now try plugging the pack into the charger and see if it will let the LED light up and try to top off your charge.

If no LED response now, with a now FULLY charged pack, try again later after you have used the pack and depleted its charge down a bit.
Somehow . . . . . I have a feeling that it will light up in one of the conditions.


73s de Edd

 

[suppala]

Today when I switched on the charger there was no voltage at the charger terminals. MY earlier conclusions must have been totally mistaken. The two batteries I tested on charger had already partial charge and read 18.22 and 17.5volts. What really happened was when I connected battery directly to only the end terminals the charger condenser has built up a charge and this was mistaken by me as power from charger output. Inow will check the fuse if possible to check without taking out pcb .....suppala

 

[suppala]

Sir suppala . . . . . . . .

Your 3 middle terminals are related to isolated battery voltage sensing and feedback to the charger.

And somehow I still think that your battery voltage got so low on the pack that it was not responding.
Indeed . . . . . now that you have connected right across the charger output to the battery terminals you were able to get a full charge on the battery.

Why don't you now try plugging the pack into the charger and see if it will let the LED light up and try to top off your charge.

If no LED response now, with a now FULLY charged pack, try again later after you have used the pack and depleted its charge down a bit.
Somehow . . . . . I have a feeling that it will light up in one of the conditions.


73s de Edd

 

[suppala]

Dear 73's de Edd,
I want to add one more line to my reply .There was a possibility that the connection of charger to power supply (115v0 was made in reverse as I mistook the wider blade of charger plug is to be connected to positive of power supply . On checking ,I found because of this every point on pcb shows positive on checking with a neon line tester and this must have caused the fuse to blow , as I left the charger unattended for quite a time . I do not know at this stage what other components got affected .
s uppala March 31, 2017

 

[suppala]

Dear 73'sde Edd,
As mentioned in my two earlier posts, my impression of charger working was wbrong. When only 2 terminals of battery was connected to charger, the power capacitor got charged and gave back the same charge when a second battery was connected .Later. I could manage to release the silicon adhesive using WD 40 oil and took out the circuit boar and on checking the fuse , the fuse was open. I replaced the fuse and this also got fused immediately. On a visual check. I found the smaller of two 250 volt capacitors was leaking and giving out brown pasty matter .
.As I did not want to replace this and face another fuse failure . When I checked condenser with a dmm , it was showing increasing and falling 0hmic values meaning condenser is not open. Do you suggest any further checks before I replace capacitor and fuse and check. I do not wish to take further chances without your advice..suppala April 11,2017.

 

[73's de Edd]

Sir suppala . . . . . . . .


Wish i could have caught you in time before blowing a fuse.
On further tests substitute a wired in 60 watt incandescant lamp in place of the fuse.
If you have a shorted FWB or a power FEET on further into the circuitry, the lamp will light up very bright instead of a normal glow and a dimming of the lamp after the two mentioned filters charge up.
Plus you should then be able to read the DC voltage across them to see if it is in the expected 160-170 VDC level..


73s de Edd

 

[suppala]

Thanks. I have seen the message yesterday itself. I will try connecting the lamp in place of fuse and let you have the findings in a couple of days . The two condenser values are 200v 220 mfd bigger one and 400 v 2.2 mfd for smaller one (c5). Maybe it is difficult to check these in circuit .Thanks again.

 

[suppala]

message continued suppala ,.The 60 watt bulb mentioned by you must be of 110 volt .In India it is difficult to get 110 volt bulbs. I do not know how critical the bulb resistance is . To get same resistance of 200 ohms , I can use 4 bulbs of 60v ..suppala .April 15,2017.....