Help-Ping Charger Failure - fixed

My 5 amp Ping charger all of a sudden stopped working this morning. Unfortunately, I am relying on this as a daily commuter.

Can someone please diagnose this? There are burn marks under this component near where the plug AC cord comes out. The part number is NTC 10D-20. Okay , the part appears to be a thermistor that suppresses current on start and opens up as the temperature goes up. The specs of this part are maximum 6 amps, 10 ohm resistance at 25C. In addition, the dc output is shorted.

Here is a picture:



Please help me get back on the road. Thanks.

looks like a blown MOV (surge stopper) .... radio shack used to have them... they work like the oposite of a fuse... the dont conduct normally, but when blown, the short out totally and dont allow voltage to get to the parts behind them.

just my two cents,,, I could be wrong...

bob in phx

Thanks Bob. You can hear a pin drop in this place. Does the brown scorch marks mean that the component overheated and burned the board? I guess the way to test is to disconnect and measure resistance. I wonder if there is also some other short in there that would cause this thing to blow?

again, this is only my guess....

I would remove it from the board. I would also check all input and output wiring, including the battery for shorts etc...

Once removed, you should be able to find a part number and look up devices with similar specs. If you test it and it shows dead short, then its bad, if its an MOV...

I would then put the new part in and try the charger.. I am guessing that this will fix it...

I think you somehow got a spike on the ac side.

bob

I tried the local Radio Shack. They no longer carry this type of thing. Any good one-off supplies out there?

http://www.radioshack.com/search/index.jsp?kwCatId=&kw=mov&origkw=mov&sr=1



bob

Thanks. I saw that right after ordering from digikey.

That MOV has different characteristics though.

* Heavy-Duty Metal-Oxide Varistor
* Provides transient voltage spike protection for 120VAC circuits
* Replaces V130LA20A MOV
* Max RMS Voltage = 130VAC, Max DC Voltage = 175VAC
* Peak Current = 6500A (8 x 20uS)

you may want to think about what really blew and why. did you get a huge voltage surge or plug into a different voltage outlet? do you have any pictures of the other side to see if any traces burned up? it would be nice to have circuit diagram too, wonder if ping would email one for diagnosis purposes.

I'll take a closer look tonight. No unusual voltage surges that I know about. It was just dead as a brick overnight.

Here are some pictures for the traces:

I can't see the part in your picture, but the the NTC 10D 20 is a NTC Thermistor inrush suppressor - used commonly in most switchmode power supplies. It should be a dark disc shaped object that looks like a ceramic capacitor.

Their function is to limit the inrush current into the big input rectifier filter capacitors and prevent a blown fuse or arcing when you plug it in. They work by having a higher resistance when cold, so the current inrush is suppressed when the charger is first plugged in. Then, they will get hot to the extent needed for their resistance to drop to a low enough value.

The 6 amp value refers to the maximum steady current. You charger probably has a soldered-in line-in fuse of about the same value. Don't confuse it with the 5 amp charging current. The line-in current is much lower because it is a higher voltage.

They all would fail in the old e-max scooter chargers. The only reason they failed as far as I could determine was substandard Chinese quality. This is probably your case - or maybe too high a resistance value.

I have some US-made GE Thermometrics CL 40's on hand. They are 5 ohm/6 amp, rather than 10 ohm/6 amp, but they should work fine - probably better - the value isn't all that critical but if the value is too high they will run too hot. The 10 ohm part seem high for a 5 amp charger.

In fact Mouser doesn't even have the 10 ohm part in stock.

PM me with your address and I'll mail you a couple.

PJD is da man, great catch. so you want the lower resistance so it doesn't get too hot while running? but high enuff that the inrush spike doesn't pop the fuse? most likely only 1/2-2A fuse? how low could you go when it gets hot? does it drop below about 1ohm? great comments.

Just noticed how old a thread this is...

Here's the data sheet for them...

http://www.gesensing.com/downloads/datasheets/920_325a.pdf

rbelisle1 said:

again, this is only my guess....

I would remove it from the board. I would also check all input and output wiring, including the battery for shorts etc...

Once removed, you should be able to find a part number and look up devices with similar specs. If you test it and it shows dead short, then its bad, if its an MOV...

I would then put the new part in and try the charger.. I am guessing that this will fix it...

I think you somehow got a spike on the ac side.

bob

Click to expand...

That 10D20 goes down to .16 ohms versus CL-40 to .11.

Hmmm... The charger output has a short....The AC side fuse is still in tact though.

Bump. That short has mean concerned. Is something else going on here?

The failure could be anything. Defective part to begin with, poor electrical engeneering on the designers part, a spike, user error, water, physical damage... almost anything. Thus my suggestion to replace the part and try it again. If it fails again, search deeper, if not, hope for a long charger life with no other issues.....

just my two cents worth...

Thanks all. I received the NTC thermistor today and soldered it in place. The charger seems to be working properly now.

from PJD? way cool, this is a great place to hang, i learn a lot. he da man!

PJD offered, but I had already ordered some from digikey. BTW, shipping from digikey only took two days from MN. I am impressed.