LVC/ 9920 problem - RC-Monster Forums

**LVC/ 9920 problem -** 11.27.2006, 11:36 AM

I recently bought this for my 9920/ 8l on 4s lipo setup in my e maxx. I plugged it in and at first it looked fine, it worked and there was no smoke. I went to drive it a few seconds later, and it worked for a few throttle pulls, then the throttle started acting weird. I would accelerate then let off, but the car would be slow to react to me letting off. I was pulling it back in because of this when it started pouring out smoke. I unplugged the battery as fast as I could, and I found the negative signal wire on the 9920 was all melted and burnt looking. Ive since tested the LVC on another (cheaper) setup, and the LVC is dead. I pulled the heatshrink off, and theres no visible damage to the circuit board. The LVC did no damage to the other setup I tested it on, it just didnt give any power to the receiver. Im hoping I just have a defective LVC, and that I can replace the wire on the 9920 and all will be well, but Im fearing worse than that. I havent tested the 9920 since the negative signal wire smoked. Any help would be appreciated.

captain harlock · 11.27.2006, 01:21 PM

Ummm...Did you pull off the heatsink from the 9920 or the LVC( if it has one)?

Serum · 11.27.2006, 02:36 PM

The 8L on 4S lipo is quite hot. With good lipo's it will take 150-175A with ease..

I hope your 9920 is still okay. And if i may suggest; get another (less hot) motor.

11.27.2006, 04:07 PM

I had driven the same set up many times before, minus the LVC. The motor couldnt have caused the LVC to die.
I should mention my truck is quite a bit lighter than a stock emaxx. I have a fibreglass chassis and mostly plastic parts, and I use 1/8 buggy wheels and tires. The 8l on 4s 4000mah max amps lipos (rated 60 amps continuous) has worked for me for a while. If I can get this LVC fixed Im going to try a 8 or 9xl on 6s next.

11.27.2006, 04:14 PM

Quote:

Originally Posted by captain harlock

Ummm...Did you pull off the heatsink from the 9920 or the LVC( if it has one)?

You mean heatshrink? I pulled the heatshrink off the lvc and there was no visible damage/ melting or anything. I pulled the heatshrink off the 9920 to look at where the signal wire is soldered on, and there was no visible damage there either.
If you did mean heatsink, I didnt pull it off the 9920, and the LVC doesnt have one.

captain harlock · 11.27.2006, 05:36 PM

ooops...I mistook it for HEATSINK and not HEATSHRINK.

sjcrss · 11.27.2006, 05:43 PM

can you post a pic of what smoked?...this might help us help you

11.27.2006, 06:32 PM

I dont think a pic is really necessary (or would show much), it was the black wire that should go from the 9920 to the receiver plug , but in this case it was plugged into the LVC, which was plugged into the receiver. Out of the black, red and white wires in this plug, only the black one smoked. That wire is all melted/ burnt looking, and there is no other visible damage.

neweuser · 06:47 PM

Sounds like something is in the wrong spot, red on black and vs versa maybe.

coolhandcountry · 11.27.2006, 08:16 PM

I think the lvc had a malfunction. I am not sure how you can tell though.

11.27.2006, 11:37 PM

Quote:

Originally Posted by neweuser

Sounds like something is in the wrong spot, red on black and vs versa maybe.

Thats what I thought at first to, but its not even possible because of the shape of the plugs. Everything was definitly hooked up right.
Something I noticed, Im not sure if its a problem, is on the LVC, the negative signal wire from the LVC to the receiver is soldered onto the same point as the negative voltage signal wire from the battery wires. So the negative receiver signal wire (about 6 volts) is connected to the negative side of the 14.8 volt battery circuit.

MetalMan · 11.28.2006, 01:09 AM

Are you using the 9920's internal BEC, an external BEC, or a receiver pack?

sjcrss · 10:26 AM

Im not saying you did this wrong or anything, but you are able to plug the wires from the esc into the plug in the wrong order...this is how the wires should line up from the esc to the lipo saver....and yes you can switch the plug around and still plug it in..cause I tried it with mine....

.............| Brown wire (plug) black wire... |...............
From Esc | Red wire (plug) Red wire ........| to lipo saver
.............| Orange wire (plug) White wire .|................

11.30.2006, 08:41 PM

Quote:

Originally Posted by sjcrss

Im not saying you did this wrong or anything, but you are able to plug the wires from the esc into the plug in the wrong order...this is how the wires should line up from the esc to the lipo saver....and yes you can switch the plug around and still plug it in..cause I tried it with mine....

.............| Brown wire (plug) black wire... |...............
From Esc | Red wire (plug) Red wire ........| to lipo saver
.............| Orange wire (plug) White wire .|................

OK, I thought the plug was shaped to not allow that, but it definitly wasnt reversed. My steering servo was still plugged into the receiver from the last time I ran it, and I matched the wire colors with that, and I matched the esc wire colors to the LVCs colors.

Quote:

Originally Posted by MetalMan

Are you using the 9920's internal BEC, an external BEC, or a receiver pack?

Im using a UBEC.

Right now Im pretty sure the LVC was defective.

sjcrss · 09:40 PM

ok.... can you try out the system without using a lipo battery....