hi there, I have a power supply of 18volt /5.5 amp.the fault is it gives 4 volt instead of 18 volt ,when I checked all the components 39E resistance and 1148 diodes were open ,I replace these components but still the fault is same.supply works with 2× 13009 transistor. please help

 

Welcome to AAC!
The area around the fuse F1 and its link LF1 looks scorched. Check that the fuse is ok and that there are no dry/loose solder joints in that area.

 

Welcome to AAC!
The area around the fuse F1 and its link LF1 looks scorched. Check that the fuse is ok and that there are no dry/loose solder joints in that area.

thanks but I've checked all..the output is 4 volts ,but not 18 , I've checked all capacitors, diodes,but the output is same at 4 volts

 

hi there, I have a power supply of 18volt /5.5 amp.the fault is it gives 4 volt instead of 18 volt ,when I checked all the components 39E resistance and 1148 diodes were open ,I replace these components but still the fault is same.supply works with 2× 13009 transistor. please helpView attachment 295951

That device clamped to the heatsink, just above the blue electrolytic capacitor, in the second photo from the right, is split open. It must be damaged and will need replacing, There may be others.

 

The trace under A looks very dodgy, is there continuity?
The area under B looks like is might have been a trace that is now gone, was there copper there?

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The trace under A looks very dodgy, is there continuity?
The area under B looks like is might have been a trace that is now gone, was there copper there?

View attachment 296033​

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The trace under A looks very dodgy, is there continuity?
The area under B looks like is might have been a trace that is now gone, was there copper there?

View attachment 296033​

at point B tere was a water spillage between mains fuse and feedback 1148 diode in series with 39E resistance. both are open .I replace them both.but the problem is when both are open the supply was on at 4 volt output,when I replace them ,the supply still gives 4 volt output.13009 in pair are both ok.the feedback transformer didn't give output at 1148 diode ,

 

n

at point B tere was a water spillage between mains fuse and feedback 1148 diode in series with 39E resistance. both are open .I replace them both.but the problem is when both are open the supply was on at 4 volt output,when I replace them ,the supply still gives 4 volt output.13009 in pair are both ok.the feedback transformer didn't give output at 1148 diode ,

OK, but this appears to be a single sided PCB so all the traces that are required would be on the bottom. If there are missing or open traces, things won’t work. I am not clear about your answer: is there continuity at A? Was there a trace at B that is now gone?

 

Did you see Sarah's comment in post #4?

 

That device clamped to the heatsink, just above the blue electrolytic capacitor, in the second photo from the right, is split open. It must be damaged and will need replacing, There may be others.

it is a silicon tube that I cut to check the transistor 13009 in pair clamped with heating,,both transistor ok but I replace them ,,still not working and stuck on 4 volts,,