Anti spark stuck on?

I have a “T-Rex” anti spark switch from the apparently now gone

It worked fine for a few months. I took the board apart to add some LED’s, and 2 cheap buck converters exploded in my testing. They were hooked up to the output of the anti spark switch.

So I’m putting everything back together, plug in the control switch. And the anti spark is stuck in the on state. Won’t turn off. Checked continuity on the button, one common, continuity switches from one pole to the other. Tested the same thing at the connector that plugs into the anti spark switch.

So. Is my anti spark switch broken? What else can I check?


I think that means you have a blown mosfet

Any recommendations for a new one. All I see is the one, but shipped to me it’s near $90.

Miami electric and @Martinsp

Looked into it a bit more. I know a guy with a hot air gun and a reflow station. So I ordered 5x IRFS7730 mosfets (4 to install, one to mess up) and I’ll just swap them all out. Fingers crossed it all works out.

Honestly you need to spend more money on a good antispark or just get a loopkey. Maybe one from @Kug3lis if he still has any.


If this fails I’ll get one from Miami boards. They are like 3 hours from me.

I’ve got other boards to ride while this one is down, no big rush.

@Kug3lis has some beefy ones.

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Everything sold out

Where art thou @goldenHusky

We were discussing this phenomenon earlier and why they blow.

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Super interesting read actually. I don’t think I can modify this switch to do the delayed resistor thing. So next time it dies I’ll just hope the fat boy switch is in stock.

I do have some xt90-s on the way. So maybe that will help.

Hey, I’m not very active lately so if somethings up just write me a pm so I get an email notification.

@marsrover001 I’m sorry for the defect, maybe some transient feed back of the buck converters at breakdown or normal operation exceeded the 100 Vds limit of the mosfets. Also the control switch should never be unplugged, because there is no pull down resistor, so the gates are on a undefined potential which can cause issues.

Btw, my site is not completely gone, I just discontinued the premium subscription of the shop software I used, where you can set your own domain, so the “bigcartel” phrase is included again like this:

That might have been it, I spent a few days testing stuff by just manually unplugging the main power lead. Do you think my mosfet replacement idea will work or did leaving the switch unplugged mess up the switch sense side?

I know I’m totally out of warranty so no worries.

Replacing the faulty mosfets (could be only one or all four) will fix it, maybe the zener diode broke down too but that is rather unlikely, you can check that by measuring the voltage from the gates to ground.


I can recommend Zill Boards anti spark. image

only if you use them as loop key and forget about the mosfet switch :wink:

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that seems like a re branded flier AS. Witch has known issues

Yeah true. Was that the 120A version or 300A with the issues?

not sure, @longhairedboy and @Jayx should know more