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I recently acquired a used and rather abused Novak t4 speed control. It came free with my car because the seller didn't know if it worked or not. So I tested it with my multimeter to find that it has a short circuit inside of it. The short is occurring somewhere between the battery intake leads and the motor output leads. How can I find exactly where this short out is? The speed control had been opened before, and has newer wires on it. (well before I removed them to find the short circuit. I checked all of the contacts and there appears to be no solder in between them. Where could this short circuit be? Can I fix it or would I just have better luck finding a used one on eBay?

probably a blown FET, but the regulator inside could also be suspect. Not sure but I thought there was a guy or two on these boards that could fix them.....

honestly though, for the price these days, you can pick up a fairly decent brushed motor speed controller for not much more than it would probably cost to repair.

sorry to hear it's not working....

The plastic around the far right transistor tab is a little melted too.

you can try removing that transistor if you are good a soldering, then see if it fixes the problem on the bench. If so, cross reference the part number on the blown part with something you can get now, from places such as digikey or mouser or etc, and replace the burned out one.

Define short circuit – The positive battery and positive motor leads should be a short, essentially the speedo controls power from the negative side of the circuit. Tekins generally use 3 wires because of this, they run a positive wire directly from battery to motor, the speedo taps into that with a single positive wire.

The melted plastic is troubling of course. Assuming we’re viewing the same, the right transistor is the brake (set off by a little plastic ridge). Not unheard of for the brake to blow, and forward still work.

Might be worth a shot to try it if that is the only short you are seeing. If so be very aware of temps of the speedo, and the battery/wires/connectors. If there is more damage, more shorts, it might pull a lot of current and start heating things up real quickly. Don’t want to add a battery to the dead pile!

Regards

I tried to plug it in and use it, but it starts to smoke after about 10 seconds of being plugged in. It also has a blown pot on the right side.

sounds like alot of work for little gain......try something like these LRP controls on associated's website that are webspecials:

http://order.aeteam.net/Products.asp?categorycode=8000.9LRP&pg=2

bottom of page....

jwscab wrote:sounds like alot of work for little gain......

my thoughts exactly. novak t4's, if you really want one, are plentiful on ebay for next to nothing.

if you really want a brushed esc, since most people go the brushless route these days, you can get great deals on competition level brushed esc's..... brand new.