XB-502 controller-need help performing shunt mod

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KBlake
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Joined: Saturday, May 28, 2011 - 14:16
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XB-502 controller-need help performing shunt mod

Hello All,
I purchased an XB-502 about a month ago, and I've been reading this forum with great interest. I decided to tackle the shunt mod this weekend, and bookmarked Richard's XB-500 mod page in preparation. Unfortunately, the controller in my bike is completely different than the one in his write-up, and the XB-600 shunt write-up. The case is all one piece, except for the ends, which are secured with two screws per end. The MOSFETS appear to be held in place by a spring clip that runs the length of the case. Since the MOSFETS are attached to the board, this is preventing me from removing the board from the case. looking in from the ends, I can't see a shunt like the ones in the 2 write-ups.

Has anyone performed this modification on an XB502?

If so, how did you overcome this obstacle?

Thanks in advance,

Ken

Kft
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Last seen: 11 years 4 months ago
Joined: Wednesday, June 22, 2011 - 15:24
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Re: XB-502 controller-need help performing shunt mod

I can report that the XB-610 has the same spring clip in place on the mosfets. I tried unsuccessfully today to remove the spring clip to gain access to the controller board. Has anybody had any luck removing the spring clip? I can see a slotted area where it rested prior to assembly, and it's my guess that it needs to be pried back into the slotted area next to it in the case to relieve the tension on it. I tried with some small screwdrivers but was unable to lift it over the lip of the case that's holding the spring in place. Aside from prying, I also tried yanking it out with a pair of pliers but that was also a no go.

michaelzhuge
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Joined: Thursday, September 15, 2011 - 12:25
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Re: XB-502 controller-need help performing shunt mod

Anyone have any updates to this? I'm also looking to shunt mod the xb-502 if possible.

Kft
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Last seen: 11 years 4 months ago
Joined: Wednesday, June 22, 2011 - 15:24
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Re: XB-502 controller-need help performing shunt mod

I've got an update. I finally got the circuit board out of the case. I ended up cutting a slot into the case in the spring clip area to relieve the tension on the clip. Afterwards it was pretty easy to remove. Unfortunately that's the end of the good news. I located the shunts and figured I could similarly install a length of coat hanger wire like people did on the XB-600/XB-500. I drilled two small holes and soldered in the wire. After putting it back together the scooter is no longer functional. Everything works as normal when switching the key on (lights, horn, gauges), except that I hear a small click after switching the key on and the throttle has no effect. On the bright side, there's no smoke or heat detectable from the controller after applying power to it, so I'm taking that as a good sign.

I haven't gotten around to desoldering the new shunt yet. I'm guessing there is an over current protection due to there not being enough resistance, I drilled through something I shouldn't have, or my shunt is causing an unintended short. If it works again after desoldering the new shunt, it probably is some type of over current protection and I'll end up trying something with higher resistance.

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