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Electronics => Repair => Topic started by: Yamin on April 19, 2021, 11:28:36 pm

Title: IR2153 based SMPS repair + checking the IR2153. (Class D amplifier).
Post by: Yamin on April 19, 2021, 11:28:36 pm
Hi guys, I've got in a Proel stage 4 class D amplifier in for repair. The fuse blown and I measured a short upstream from the bridge rectifier +Ve and -Ve. The two shorted components were the High and Low Mosfets. Gate-drain-source shorted on both. After removing the two mosfets the short has cleared when measured from the rectifier.
I haven't figured out the root cause for the  failure but I have measured one dual diode on the secondary side (channel 1) which is shorted. I would need to further investigate.
My question is what other things I should look for while trying to fix this? I don't want to be just replacing MOSFETs just for them to blow up. What would be the best strategy?Could this short on the secondary side cause this kind of failure of the transistors?
I tried to look for schematic for the model but couldn't find one, by the looks of it it looks like a standard IR2153 circuit with feedback.
Thanks for the help.
P.s: there is some kind of 'oilish' substance on the dual diodes on both the channels.
Title: Re: IR2153 based SMPS repair + checking the IR2153. (Class D amplifier).
Post by: Yamin on April 20, 2021, 10:07:18 pm
In addition to my post 1, I also wanted to ask about how to check the IR2153 using an external power source.
At this point I have got the shorted MOSFETs out of circuit. I soldered to wires to VCC and COM pin of the IC and applied 10V from a bench power supply.
I measured the voltage at Gate - Source pads for the high and low transistors.
High = 0.0V (G---S)
Low = 4.9V  (G---S)
I haven't got access to an oscilloscope at the moment but its my understanding that I should be able to measure something around 1V or something if its properly switching.
First question is whether I'm doing this right?
Second question is can I assume that the IC is toasted?
Visually the IC looks okay and the diodes and resistors to the gate measures out ok.