48v charger goes phhhzzzzt

[zap]

I asked this over in scooters and have had no reply so I'll try here

Plugged in a 48v Panterra sla charger and got a flash and magic smoke. Here's the damage (I mirror imaged the trace side (2nd photo) so things line up):

The orange circle is a leg of a capacitor that had been pushed down and the solder pad broke away from the trace at some point in the charger's former life.
Do you think this is what caused the resistor to blow?

Some more picture of the charger:

If anyone has this charger and can open theirs up and give me a value for "RU1", I would appreciate it.

If anyone wants to make a guess at what the value might have been, I would appreciate that too.

Thanks!

 

[heathyoung]

Well, since that appears to be in series with the mains input, I would be saying that it was probably an inrush current limiter (PTC) - you should be able to salvage one from an old PC power supply.

 

[dnmun]

i agree, looks like it is an ICL that blew. but i am really confused by looking at the picture of the underside. did you invert that image with when you posted it under the front side?

i have some big ones here, 6.3A rated and reads NTC for negative temperature coefficient, since the resistance drops as it heats up with the current flowing through it. and 5.0 for 5 ohms as the initial resistance. this is bigger than the ones that come stock and will never fail on these small chargers.

if the capacitor is still in contact with the pcb trace it may still be ok, but you could scratch off the shellac and solder a wire onto the trace over to the lead of the cap, and use silicone or liquid nail to glue the cap securely to the pcb. just enuff to keep it fixed to the board.

i have sold about 15-20 ICL so far, i think maybe 10 chargers fixed now, maybe a dozen.

 

[Doctorbass]

The exact same problem happened to 5 out of 7 of the 48V 5A aluminum cahrger from pinbattery..

I soldered a jumper and they all work nice since 1 year now.

Generally they blow when they are connected to teh same breaker circuit than a compressor, refrigerator or other electric stuff connected to teh same circuit and that generate voltage spikes when they start.. that voltage spike travel in the 120V circuit or your house and can blow things like that.


Doc

 

[zap]

but i am really confused by looking at the picture of the underside. did you invert that image with when you posted it under the front side?

Like I said, I mirrored the image so everything is in the same place.


I was pretty sure it was for inrush but I had no idea what value to look for.
Here's a bigger picture... I don't think it's any type of thermistor.

Doctorbass, there wasn't anything else powered on when this was plugged in. I hope it was the capacitor that was lose that caused it to blow.


Thanks all for the replies.
I need to re-solder the capacitor leg and while I'm doing that I'll either toss in a new resistor or maybe like doc said, solder in a jumper.

 

[dnmun]

nope, it is a thermistor like heath said. not a resistor. usually they say VR1 but yours says RV1 but you can measure the resistance across it to see what it says. if it is 5ohms then it is ok. the resistance drops to something like .2 ohms when it is running, but with all the heat from the current causing it to age prematurely. the chinese thermistors just seem lower quality than the ones i found at mouser. plus i got the large ones.

 

[zap]

Many thanks to all who replied!

I grabbed a SCK 053 off an old pc psu and stuck that in, scrapped some copper from around the bad capacitor pad and resoldered that, and resoldered the "iffy" line in wire... everything worked

At first the led worked but when I put it back together I could hear the fan but the led weren't working...
I had put the lid on 180° from the correct position Heh... the simple things...