No Throttle…Now what have I done?

[greed4speed]

Good Day, I have been an active ‘reader’, but never a member ’til now. I’ve really never needed to post before; nor have I ever considered myself worthy to contribute in light of those who manage and post regularly. Besides, most answers to problems can be found readily through a search, but now I have a dilemna.

I blew some fets 2 weeks ago, so I decided to replace them with a 2×2 stack seeing as how I only run a spinbrush hybrid on 7.4 li-ions. However, after installing the new fets…I have found that I have steering, but no throttle (forward or reverse).

(forgive my laymen terms for lack of proper terminology)
I tested the power to motor by placing the leads on the board where the motor wires connect…nothing but an occassional .01 to .04 when I apply throttle on the controller. I then placed the negative lead to the board where the negative battery wire connects and kept the positive on the ‘motor connection’ and I’m getting a full reading. Evidently there is something wrong b/t those two points.

I have tested the fets’ connections w/ the multimeter (not sure if this is profitable or not…but I did it anyway) by comparing them to other working xmods. It appears that all the ‘legs’ are soldered properly w/good contact and no shorts.

I am really at a loss and my biggest handicap is ignorance. I was wondering if someone might suggest something other than completely replacing my board.

[betty.k]

dunno if i have any answers but a good pic might help.

and don’t worry about joining in more, we’re all idiots in our own little way:smiley8: :8ball:

[PandaBear]

Taking too long to install your FETs might see your soldering iron sit on them for long enough to toast them… did you take more than like 30secs to solder them on?

Could be something else on your board that’s damaged; or perhaps think about the piggyback “Whoa Nelly” creation.

[greed4speed]

Here are some pics of my EVO’s board: (ashamed of soldering skills:blush: )

Here’s the underside of the board.

EDIT UPDATE:
I’ve been working on this for about 3.5 hours now. Earlier, while I re-checked the fets’ connections again (each little leg at a time) forward/reverse, I realized that one of my stacked fets had a tiny seperation…I touched up the solder job and now I have reverse. Being inspired, I re-examined all the remaining legs but found nothing else ‘visibly’ wrong. This is very frustrating as I have been going from point to point on two seperate boards-checking voltage-forward-reverse-making a note on it, then moving on to the next.

I wish I knew exactly how to trace power from the batt’s to the motor connections; perhaps then I could find out why my negative connection point doesn’t register. The board is very confusing to my untrained eye.

Back to the fun…

[betty.k]

that soldering aint so bad, want me to get a pic of my “clifford the cricket” for ya?:D

i’m still not sure (i’m no techo) but it’s often worth asking the obvious questions.
are these specifically evo fets you used?
there is a difference between evo fets and all other fets (i waver, mini z, 1st gen xmod), so if you didn’t use the right ones then they won’t work.

and as panda mentioned, overheating these components will kill them:8ball:

[greed4speed]

Thank You for the reply and kind words on my soldering butch.

Yes they are the IRF7324 and the IRF9910. I placed each of them in the proper places w/ the ‘dots’ facing the correct direction according to ph2t’s FetInstallationGuide

I don’ think they are blown b/c I have tested each of their little legs. Of course, not all of them give of a voltage reading, but they don’t do that on my other xmods either.

This is why I ‘think‘ (famous last words) that it is something to do with the board…but I really don’t know. In the past I have had ‘traces’ burn in two which was easily fixed and readily identifiable…but this is something else :huh:

I understand that it’s hard to help w/o fiddling w/ the car for yourself…I was just hoping someone would know off the top of their head what would cause such a problem.

[BludyYank]

At what points are you ‘testing the legs’? Through the fet’s themselves or through a circuit to the leg? Could be that one of the contact pads has lifted from the board despite being properly soldered to the fet leg. I went through 2 Evo pcbs stacking and restacking because I was melting them off with the motor/li-po combo’s I was testing. Thought the boards were toast. Got an Evo Nelly and currently revived one of the boards. Seems the contact pads on the Evo pcbs are easily destroyed. I even had to scrape into one of the circuits to get a contact point.
As previously mentioned, if you can solder quickly and accurately, you can be successful with upgrading fet’s on the Evo. Otherwise, the best bet’s an external.

Just an aside: Not that I don’t have enough to deal with currently but I can’t wait for more Nellys to be back in stock, have a few other projects in need.

[greed4speed]

Thank You BludyYank,
I have tested them at the contact point first…then I tested at the top of the uppper fet’s leg. (My mentality was: if it were properly soldered to the contact pad, then there would be a reading) However, this does bring up the question…why do only some of the legs register on the my multimeter? I have an XMOD EVO that is still fully stock (as far as electronics go anyway) that I have been using as the fet’s activity ‘blueprint’.
(in the meantime, I’ll be searching the forum to see if it’s already been exlplained; unless if somebody wants to just ‘give’ me the answer and promote my laziness! J/K :smiley16:)

And yes, I also have had to dig deep into the board to make contact, and even make my own traces due to self-inflicted damage…I feel your pain from scrapping other-wise good pcbs.:smiley6:

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