How to repair battery charger

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champ1

Joined Jun 4, 2018
103
I have a PCB of battery charger which I would like to repair for my friend

I think below part of PCB has been damaged

upload_2019-4-27_16-24-35.png

The full specifications of the charger can be found at

https://www.connevans.co.uk/product/10483097/DCM4392/MED-EL-DaCapo-charger-for-Powerpack-batteries


I have attached a picture of the charger. Look at the attachment

I don't understand how to start troubleshooting. It seems it can work with two power supplies 230 V AC and 7 to 15 V DC

I want to check the power supply circuitry first

1) Which is the power supply connection on the board (AC and DC)
 

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Dodgydave

Joined Jun 22, 2012
8,571

Thread Starter

champ1

Joined Jun 4, 2018
103
You need a Dvm or Voltmeter to check what the output voltage is, your circuit uses a TNY266 smps chip.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.power.com/sites/default/files/product-docs/tny263_268.pdf&ved=2ahUKEwiiz7HBkfDhAhUyVBUIHb-oCDoQFjAKegQIAhAB&usg=AOvVaw1O0E1eBQ9MP1fzd8JNkxkc&cshid=1556363451979
So it can pulse the mains directly give out the desired voltage.

Warning!! This circuit uses Live Mains...
I have a multimeter to check voltage




I don't understand where to apply main supply on the board. Where to connect three wires on the board?
 

LesJones

Joined Jan 8, 2017
2,417
If you can't work out which connections are the mains input then I think your knowledge is too little to attempt to repair a switch mode power supply. I can guess the mains connections but I would at least want to trace out the schematic of the input side of the switch mode regulator before applying power.

Les.
 

Thread Starter

champ1

Joined Jun 4, 2018
103
If you can't work out which connections are the mains input then I think your knowledge is too little to attempt to repair a switch mode power supply. I can guess the mains connections but I would at least want to trace out the schematic of the input side of the switch mode regulator before applying power.

Les.
I think below red points would use for main supply

upload_2019-4-27_17-14-54.png
 

LesJones

Joined Jan 8, 2017
2,417
That would also be my guess. I suggest you first check the components between those terminals and the input to the bridge rectifier with your multimeter before applying power.

Les.
 

drc_567

Joined Dec 29, 2008
751
... suggest looking for parts that may be burned out ... there are one or two carbonized traces that may indicate a problem of some sort. Try to desolder the bad parts and see what they are. It is not a good idea to check for mains power if there are obvious problems.
 

Thread Starter

champ1

Joined Jun 4, 2018
103
... suggest looking for parts that may be burned out ... there are one or two carbonized traces that may indicate a problem of some sort. Try to desolder the bad parts and see what they are. It is not a good idea to check for mains power if there are obvious problems.
I think the mentioned part R1 R1 has been damage I can't see their value because it has been burned

upload_2019-4-27_17-34-28.png
 

MrAl

Joined Jun 17, 2014
6,785
Hello,

Just buy a new one they probably are not too much money.

If the resistors are burned, then something else might have shorted out that caused that.
To fix something like this you need a complete schematic and you also have to be able to perform certain tests after the fix. It's not just about measuring voltage either. This is especially important if the battery technology is Li-ion or similar.
Do yourself a favor and buy another one :)
 

Thread Starter

champ1

Joined Jun 4, 2018
103
Hello,
Just buy a new one they probably are not too much money.
It's too costly for me

Well I will try to sort out the problem because I have a chance to learn something new and I can save money

If I will care only about my life then I will never learn new things in electronics

I would like to change two resistors on the board but I don't know what would be the resistor value. any guess
 

Externet

Joined Nov 29, 2005
1,419
The possibility of the charger behaving properly as it should is not being considered.
If the cells/batteries to be recharged are in a state of overdischarge/abuse/bad; the charger will refuse to work, by design.

Did you measure R1 R1 value ? Some knowledge is necessary for you to attempt diagnostics/repair.
 

MrAl

Joined Jun 17, 2014
6,785
It's too costly for me

Well I will try to sort out the problem because I have a chance to learn something new and I can save money

If I will care only about my life then I will never learn new things in electronics

I would like to change two resistors on the board but I don't know what would be the resistor value. any guess
Hi,

Well ok then.
The only way to know for sure what the values are is to get a schematic. Maybe look on the web sometimes they show up sometimes not.
Sometimes the resistors just get dark colored but are still the same value. You could try toi measure them.
But as i said before, if they got dark then there is likely something else wrong too which is not as apparent. If something down the line burnt out it may not be visible but it would just mean burning out the new resistors too.
Unfortunately fixing electronic devices is not like fixing say a kids swing set where you see the broken chain and get a new one and replace it
and suddenly it works again for years. Yes, we do get lucky sometimes but it's not that easy. If you can find out the values you may get lucky.

Oh another thing you can do is trace out the entire circuit very very very carefully and draw a schematic. You could present the drawing here and we can try to figure out what values they are likely to be. I've done this before so i know it works. Still have to be a little lucky though.
 

Dodgydave

Joined Jun 22, 2012
8,571
I have a multimeter to check voltage




I don't understand where to apply main supply on the board. Where to connect three wires on the board?
The two Springs look like the mains input, (Red and Black) wires...don't connect the Green earth wire..

Looking at the pcb i would say that something has blown around the bridge rectifier input...Prepare for a Big Bang when you power it up on the mains.
 

ScottWang

Joined Aug 23, 2012
6,843
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