Perun v3 Optical blowing fuses

I’ve just finished soldering and wiring up the perun v3 optical mosfet as per the instructions, and used the 25amp fuse. I get to the calibration stage, pulled the trigger until the beep stopped as per the instructions, then pulled the trigger again and the fuse blew. So i put in the 40amp fuse, then as i connected the battery the fuse blew immediately. Can anyone tell based on this what i have done wrong?

battery is a nanotech 6000mah 25-50c, 11.1v with xt90 connector.

some research tells me I might have a short circuit somewhere.

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The area around the motor terminals may be shorting on the metal motor cage ?


thanks for the suggestion rattler. will look at this area first.

I would suggest you remove any sharp edges off the motor cage, the rubbing of the wires in use will cut through the insulation and give shorting issues down the track


Have you tried removing the motor from the cage and running it ?
That will tell you if it is that or if you have a multimeter you could find the problem

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good advice. will try sometime this week

Yep I would start by looking for some short circuits. Definitely cover the motor termimals with heatshrink or something.

Go back through the wiring and making sure there’s no splits or anything exposed touching metal.

I had the same issue with one in a v2 Retro Arms gearbox and the small signal wire had split and was arcing out on the housing.

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i’m curious about the xt90 connector…

serious overkill…any reason why you selected that one?

haha yep. it came with the battery. (also serious overkill)

for all the effort you’re going to with wiring and build shit…swap them out :slight_smile:

or rather…i would (which really isn’t any reason to follow suit…or is it?)

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Well he might have an issue trying to solder those enormous battery wires into the tiny XT30 connectors :+1:


Not with that attitude he wont anyway



nah i’ll definitely be leaving them as is.

ok i’ve identified the motor spring within the motor cage as creating the short. i have the spring under compression within the cage. is this correct?

second issue, now when i plug it all up and connect battery, the motor runs without pulling the trigger, regardless of the selector plate position. im not sure how to reset/recalibrate now…

You will have to follow this procedure


You should always do this before trying to fire


yep so am doing this and getting stuck at stage 5/6. it doesn’t seem to be recognising me touching the sensor.

thank you. i will have to buy one.

Try using the extra reflective tape stuck on something to replicate the selector plate and move it twice quickly like you would if it was together.
Make sure you understand the procedure exactly.