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help to identify R2 resistor for a battery charger

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tomos

New Member
Hi all,
I have a B&D battery charger doesn't want to charge anymore, just opened it an found the R2 resistor blowed up, I can't recognise the resistor because the coating is burnt and I can see only the inside spiral, wondering if someone could help me to find out what resistor I need to restore the charger.
I was able to fix the battery that blowed the charged, a couple of cells were bad, but I'm not really good with the ohm's law so I need some help.

the charger:

input 230/240V-50Hz-40W
output 23V-1A-23W

the battery is 18V

Many thanks
 

Grossel

Well-Known Member
Hi.

There is no way I can tell the value. A close up picture might help. But as you said, a completely burnt out resistor is very hard to tell it's (former) value.

But since I like betting, I'll bet it is 2.2 ohms. Most probably it was even smaller.
 

tomos

New Member
Hi Grossel, thanks to reply back.

Here some pics of the resistor,




surfing on the web I found some infos about how to identify a burnt resistor:

1. Carefully scrape the burnt coating off the surface & you will see the spiral.
2. Measure from each side of the break to the end leed with an ohm meter.
3. Add up the 2 values & that's about the 'ball park' of the original value.

honestly I really don't know if this is work or not but I did a measurement as he suggested and i got 63+63 = 126



I could try to fit different resistors from low to high (as you suggested 2.2 ohm or lower)
but what about the Watt of the resistor? any idea about what should be right for this charger?

Thanks again for your help
 
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crutschow

Well-Known Member
Most Helpful Member
Did you measure from each end of the break or end to end? If end to end then the resistor was probably about 60 ohms.

The resistor appears to be about a 2W device.

The problem is, do you know what blew the resistor? If it was a failure of another device in the charger, then just replacing the resistor won't help.
 

Grossel

Well-Known Member
Hi.

It might help if you also take a piture of the print side AND the device itself.

As mr. crutschow says, there may be another part that cause it to burn. A couple of aditional pictures might give an idea of what that can be.
 

tomos

New Member
Hi guys,

here more pics











I'm not sure what blew the resistor, what I know is that I tried to recharge a faulty Ni-Cd battery (I found out it was faulty after the charger failed so I open the battery and I found 2 bad cells) and I guess the charger burnt the resistor for this reason.
Both the led working, the transformer output before the circuit is 22.8V

I have measured the resistor from each end of the break (the 2 red arrows on the pic show where I placed the tips of the ohm meter)

Many thanks

Tommi
 

Grossel

Well-Known Member
Hi. You can also read the text printed on transistors Q1 - Q6.

I've revealed some of the paths. It seems that D5, Q1 or Q2 is making the burn happends. Those is the only components that is directly connected to your burned out resistor.
But, that is not completely sure. It might as well be something else that getting Q1 or Q2 to turn hard on.
 

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tomos

New Member
Thanks Grossel,
You are really kind to spend time to reveal the path, at this point I don't think to be able to go ahead (I'm not an electronic/engineer guy) and don't want waste other people time, I thought that the faulty battery blew the R2 resistor, I didn't find any fuse inside the charger and I thought the R2 was working like a fuse, sounds it's more complicated to me and as you said It might as well be something else that getting Q1 or Q2 to turn hard on
I don't have the skill to test all the other parts to identify the fault, I try to "recycle" stuff before throw away and buy new one, I'm good with mechanic but not with electronic stuff...
Thanks to mr. crutschow too,
I have really appreciated your suggestions guys,

Regards

Tommi
 
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KeepItSimpleStupid

Well-Known Member
Most Helpful Member
I'll bet it was a lot lower than 60 ohms. I'll go with the 2.2 ohm estimate. 23 V / 1A is about 2.3 ohms. More like 2.2 ohm 2 W wire wound.

That component would act as a fuse.
 

tomos

New Member
Thanks micr0man, if you can get the value should be great...
a big thanks to everybody trying to help.

tommi
 

nickb551

New Member
Hi,

Just came across this thread while looking for info to fix my B&D 18V charger - mine is a slide battery type but has a virtually identical circuit & the same failure on mine, R2 burnt out. Did you ever find out what value/rating R2 was ??

Thanks,

Nick
 

mars1

New Member
111.jpg
I have the same charger B&D 18V. What is the exact model number of the transistor - Q1 ?

Thanks
 
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