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ianc
2008.12.11, 01:58 PM
Hi guys,

A buddy of mine blew up his AM car running LIPO. I looked and both stacks of FET's were blown.

I removed them and soldered on two new 2X2 stacks, then tested, but I only have reverse; no forward. I tried reflowing all the joints, but no joy. I'm sure there is no connectivity between adjacent legs of the FET's in the stacks.

How would I go about troubleshooting something like this? I don't mind pulling one stack off and resoldering it, but how do I know which stack is having the problem, or even which leg on which stack?

Could it be a board problem instead?

Thanks for any help in getting me started down the right path...

ianc

byebye
2008.12.11, 08:37 PM
Pull them and run a single stack and check it again. If you lose the FET furthest from the black box that is the reverse FET(they work together but if you lose one stack it only affects the forward or reverse).

Let us know how it goes.

Kris

ianc
2008.12.12, 10:43 AM
Hi Byebye,

Thanks for the post! With the help of the pic on this page:

http://mini-z-guide.com/mosfet.htm

I was able to successfully track down the cause to an incomplete solder on the forward N gate pin. Problem fixed!

ianc

Action B
2008.12.12, 10:57 PM
If you run lipo, do you need more than a double stack 8858? I was just wondering. I don't usually run my lipo pack but if one of my friends wants to challenge me to drag race their Xmod, I would pop my lipo pack in for a minute. I am going to be running a pretty hot motor (atomic T2). I could do a 3x3 but I don't want to give up too much throttle control.

ianc
2008.12.14, 03:51 AM
My friend was running an ATM stock-R. He said he ran it quite a # of times before it blew. Whatever.

After doing the 2X2 FET job, I drilled a stock Kyosho motor for his atomic mount and knocked him down from an 8T to a 7T. Let's see if this can last, 'cause he doesn't know the meaning of the word 'maintenance', and I really don't feel like doing this again...

ianc

Action B
2008.12.16, 05:13 PM
I kinda like doing FETs...