Yet another way to fry controller!

Just got my project finished ... a 24v "PowerTow" airplane tug. Looks sort of like a garden tiller, has arms on the front to grasp the nosegear lugs on my Cessna 206. I use it to push/tug the airplane (2600 lbs) in and out of the hangar. I found a 4.5 amp, 24v gearmotor with a 20:1 reduction box on eBay for $60 that works great. I ran a belt drive from it with about a 3:1 reduction to a jackshaft where a sprocket drives a chain on the single wheel, the final drive sprockets give about another 5:1 reduction. I power it with two 12v 7.5ah SLA's in series. A 30 amp YK48-2 controller from TNCScooters is used with a thumb throttle and a simple forward/reverse toggle switch for control.

Everything was working perfectly! I had mounted a battery charger jack on the top of the project box that contained the controller and wiring. I got a "bright idea" to check the battery voltage by touching voltmeter leads to the prongs inside the charger jack. The "bright idea" got even brighter when I was greeted with a loud "ZAAPPP" and a flash of sparks! Apparently I shorted the positive terminal against the side of the charger jack with one of the test leads.

The "ZAAPPP" apparently fried the controller. Now it immediately goes to full speed forward when switched "forward" or "reverse" and the thumb throttle is totally ineffective.

Well, another Y48-2 is on-order ... hopefully, that's all the damage I did! Just thought I'd relay this to save some other poor soul some grief!

Regards,
John