dnmun wrote:how did your charger die? usually they fail when the ICL blows up.
did you take either of the 2 chargers you said had died apart to see what happened?
we have been able to fix most of them for a few cents each.
dnmun wrote:you asked at the beginning of your thread how to fix them. we have been able to help a lot of people fix their chargers but you have to open it up and measure the voltages as they go from the front end to the back end and include pictures so we can offer advice. we should be able to get them both working again.
miuan wrote:I've had two of them fail.
The 240W unit appears to be dead on arrival, only the green light is lit, and no red light. It stays cool. Output is zero volts. It looks mint inside, no loose parts either.
The 900W made quite a lot of smoke last time I used it but it still worked. Haven't used it ever since, I need to have a look what's broken inside.
As for Evassemble: I'll never shop with you unless the calculator yields a much more sensible shipping cost for my location. 150 USD for a 3.5kg item is ridiculous. Also, is the speed specified for BPM motors at 36V or 48V? Come on Michael, your sig says you can do better, prove it!
dnmun wrote:ok buzzing. you will notice that the Switch Mode Power Supply SMPS has a front end and a back end, separated by the transformer. there is high voltage AC in the front end and it will sting if you let it touch you but if you can find where the output from the rectifier bridge is applied across the terminal of the capacitor on the front end, there should be a DC voltage with AC ripple on it.
that DC is switched at high frequency through the transformer by the power mosfet you will see in a heat sink on the side. when the current is switched through the transformer, it induces current in the output that goes to the back end. should be about 5 legs or maybe 6, some to the output and some supply current to the op amps and other parts.
the pulsing DC output of the transformer into the back end goes through a schottky diode into the output section which has the output cap on it and that cap smooths out the ripples in the output voltage from the switching. so just look and familiarize yourself with how it goes from front to back and see if you can measure the voltages on those traces. the wire shunt is where the delta voltage is generated to be used as feedback to the op amp that controls the amount of current that goes to the output. so you will find a trace from the high side of the shunt that goes over to the op amps. but if it is buzzing and you don't have any voltage in the back end then we will look more at the transformer leads. BOL, dm
miuan wrote:The 900W made quite a lot of smoke last time I used it but it still worked. Haven't used it ever since, I need to have a look what's broken inside.
dnmun wrote:the pwm frequency is so high you would never hear it i think. do you have a picture of which big resistor that was and what the value is? the fan would be turning on when the op amp that controls the output is telling the front end to send juice to the back. so maybe the current is not getting through to the back end like it should. these with the TL494 are different from the newer designs, but the 5W resistor may be a clue.
pradeepswain wrote:The capacitors right next to rectifier rated 200v are showing 166v on multimeter. Is that the starting point in the circuit?
pradeepswain wrote:Thanks for the detailed information. Took a while to check the remaining circuit from following your comment.
I guess I've found the faulty part. The transformer YC-4803J does not show anything significant in output side. The input 4 legs show DC287v each. But voltage on the 6 legs on secondary side is 0.2v. I presume it should also have a fluctuating DC voltage. Or could it be the switching transistor that's feeding current.
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