Beginners Snap On Battery Charger Repair Project

[Cactus]

For my next beginner's repair project I picked up a broken power tool battery charger. I have no idea of history other than it stopped working and the circumstances around that are unknown.

On opening up the case, I saw that the mains +ve supply wire feeding the board had been nipped between the case top and bottom during assembly however it is not broken. I checked the board both sides and saw nothing obvious amiss other than a great big chunk missing from an opamp. For info I have attached some pics that lead to my questions.

Is this usual to see this sort damage thing when an opamp fails and why would it fail this way?

I have removed the opamp from the board but as it has no markings on it anymore how do I find out what to replace it with?

I'm sure you will tell from my questions I am out of my comfort zone here so any thoughts members have would be really helpful.

[ArthurDent]

The blown U1 is not an opamp but a SMPS controller chip that controls Q1 that is in series with the primary on the transformer covered in yellow. Q1 feeds a high frequency (50Khz?) signal to the transformer. There is probably more than just that chip blown.

Here's a typical schematic that shows a similar chip in blue.

https://img.bhs4.com/f8/6/f86356b388e38ed22898d1a074c700f5c88f92ba_large.jpg

[Cactus]

Thanks Arthur, Im going to shuffle off for a bit to digest, research and learn. I will be back as soon as i get my head around things and understand bit more......... It looked a bit like an opamp