Need help repairing a 12v car battery charger

Thread Starter

John JJ

Joined Aug 15, 2019
16
Hello Guys
Im new to this forum and also a beginner to electronics. Im just trying to repair a 12v car battery charger. It would not switch on so I opened it up and had a look. Circuit board looks good (nothing looks burnt or suspicious looking) and tested AC voltage which seems to get as far as the transformer. I have no DC voltage on the other side of board
Thanks image.jpgimage.jpg
 

AlbertHall

Joined Jun 4, 2014
8,364
This a switch mode power supply and if you are not familiar with them I don't recommend that you attempt repair as they can be dangerous. Over half of that board is at mains potential and so not safe to touch. Also when things go wrong they can fire parts of components at you and your eyes.

If the fuse is intact buy a new one.
 

narkeleptk

Joined Mar 11, 2019
372
I agree with @AlbertHall that replacement is the simplest solution and you probably shouldn't poke around while its powered with out a healthy understanding of the unit. Still, there are plenty of things you can check with the device disconnected. I know little of smps but in cases like this I usually just check over some basic stuff like the diodes, relays, shorts in ic's, and any other easily testable component. If that all turns up with nothing then its more efficient for me to just replace it.
 

oz93666

Joined Sep 7, 2010
669
Look at all that complex circuitry !!

Whats wrong with an old fashioned transformer and a full bridge rectifier ??? nothing to go wrong, nothing to break down .
 

Thread Starter

John JJ

Joined Aug 15, 2019
16
Thanks guys. I will get in touch with the manufacturer to see if a board can be got as a spare part. It’s a Ring 12v battery charger
 

Dodgydave

Joined Jun 22, 2012
8,389
It's a Switchmode psu, if you're not familiar with these, then it's wiser to bin it and buy a replacement one,

otherwise what is the number of the 8 pin chip on the bottom picture?
 

Thread Starter

John JJ

Joined Aug 15, 2019
16
It's a Switchmode psu, if you're not familiar with these, then it's wiser to bin it and buy a replacement one,

otherwise what is the number of the 8 pin chip on the bottom picture?
It's a Switchmode psu, if you're not familiar with these, then it's wiser to bin it and buy a replacement one,

otherwise what is the number of the 8 pin chip on the bottom picture?
Its FAN7554 is the number on the 8pin chip. Is it possible to test the chip?
 

debe

Joined Sep 21, 2010
1,141
I would check the Resistor that feeds P7 on the chip Vcc. This resistor kick starts the unit, if its open circuit or too high resistance it wont start.image.jpg
 
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