Reverse polarity on my DC converter: Game over?

[cwah]

Hello there,

I purchased this converter from Zenid:
http://www.zenid.com/converter.htm

But by mistake I put the output to the battery and input to the controller... I heard a small bam.

And now my 72V to 12V converter isn't working anymore.

I opened my converter but can't see what to fix:

Isthere something I can easily do? Or shall I throw it away?

Thanks

 

[dnmun]

unsolder the input cap. check to see if it is shorted, or blown open. use a voltmeter on the ohmmeter scale. if good the readings will change, then reverse the leads and the measurement changes in the opposite direction, if it is still functional.

 

[cwah]

Thanks for your answer.

Is this one the input cap?

 

[Ykick]

That's some sort of cap but not a polarized type. The ones sensitive to polarity are the large electrolytic's in the can package. One of those is probably not too happy...

 

[bigmoose]

If you put 60 volts or so into the output, you should check the output electrolytic caps (round aluminum cans- read the voltage on them, one will be rated high voltage (input cap) and two are likely lower voltage (output caps)), also see if you blew a board trace on the PCB, and since silicon blows before copper, the control IC could be toast if you overvolted the feedback op amp in the controller IC. 12 volts systems don't take 60 volts too well.

 

[dnmun]

i was thinking he had just applied the reverse polarity to the input. never thought it might have been applied to the output. of course it could be both, reversed to the output.

you need to unscrew that clamp on the side of the case and get the pcb out so we can see the underside of the pcb. the big blue cap is the input cap. we can only hope there is a protective diode somewhere in there.

take a close up of the underside of that pcb.

 

[cwah]

Is it that the electrolytic cap (round aluminium can) I should check the voltage?

And here's the back of the pcb:

Can't detect anything wrong?


My knowledge in electronic is close to 0, not sure if it would be better to give up :?

 

[dnmun]

sure you can give up, or you can look at the traces and follow the current from the place where it enters on the red wire. this is how everyone learned electronics.

it goes to the middle leg of that transistor. you could read the part number, google up the specs and use that to guess what it is doing. let us know.

then the adjacent three legged device in that heatsink appears to be a dual cathode schottky diode, and the current comes off that wide ground plane. what is the part number on that 8 pin IC, google up the specs and see if you can guess what is doing there.

the single big blue cap is the one that i figured was reversed, but we don't really know if you reversed the voltage polarity or put the 72V on the 12V output.

if that cap was reversed, it would be dead now. that was why i said you could test it to see if that is the problem. like i said, you can test a cap by using the ohmmeter scale on you meter.

ps: you only have to unsolder one leg, you can leave the other leg in the circuit and measure it that way.

use the high resistance range for the setting, unsolder the cap, put the red probe on the plus side of the cap, and if it shows a reading that is slowly increasing, you can reverse the probes and put the black probe tip on the plus of the cap briefly and see if the reading decreases as you do that.

if the cap is shorted it will show zero ohms resistance when you put the probes on it. if the cap is blown open circuit then the ohmmeter will not display a number, it will be over ranging.

 

[cwah]

Sorry for the late answer. Takes me time to read and re-read that. I'll look at it a bit later and come back to you when I've done my homework