Siemens SITOP 20 switch mode powersupply

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maxim10373

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Hi friends
I am try to repair this SMPS Siemens SITOP 20 .
When I switch on the powersupply Power transistor getting blast.
I changed all capacitors and faulty componants on control board
The original powertransistor they used ON5134 and I trieng BUV48A.
I could not find datasheet of ON5134 . Can I use BUV48A insted of ON5134 ?
There are two power transistor used as same nomber only one got shorted.

Thanks
Maxim
 

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You say it bloWs as soon as it switchs on.
Something bad with the circuit.
What is gate voltage on fet when you switch it on?

Is high voltage somehow getting through to your control circuit

When unplugged and ALL CAPACITORS DISCHARGED....what is resistance bewteen live and neutral.?....or vdd and ground if its not offline psu.

Be wary of using 10:1 probe on high voltage circuits where you may need 100:1 otherwiwse you blow your scope too.
 
I think before even contemplating a replacement you should find out if it is actually a bipolar transistor at all. If it is the main switching device it is more likely to be a MOSFET.
BUV48A is a BJT.

Brian.
 
That transistor can be very old
800V SILICON NPN TO-3P PHILIPS
And BUV48A can most probably be an equivalent.
 
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