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Action B
2011.03.08, 05:30 PM
So, as many of you know I do FET work and also repair boards. I have posted a lot of pictures of my FET work but not once so far a board repair. Here is a repair I recently did for a member on this forum.

Here is a picture of the board before the work.
http://farm6.static.flickr.com/5016/5510554560_a1a9ff618c_b.jpg
http://farm6.static.flickr.com/5056/5510554948_7f98241afe_b.jpg

As you can see the board FET pad #3 is burned up on one FET from each side. Luckily, on a working board I know FET leg 1 and 3 are continous with each other (respectively, meaning 1-1 and 3-3 from each side) and are for negative/positive gates on the FET so all that is necessary is a jumper wire from one side to the other.

Another issue on the bottom side if you notice there is a resistor "103" that entirely burned off. This is a tricky repair because of the size. Its a must on this side to both bridge the FET leg with the jumper wire and slide some solder over onto one side of the resistor 103 since its original pad is completely gone.

Finally some FET legs were lifted on the drain side, these are easy because they can just be all smooshed together with solder as long as some of the original pad is still present.

The end result is VIOLA, a working board. I'll post a video later but I assure you it works on bench test. I also ran a board with this same repair in a recent race and it held up just fine.

Finished product:
http://farm6.static.flickr.com/5253/5510517904_2eef76a0b8_b.jpg
http://farm6.static.flickr.com/5091/5509916357_512c82877d_b.jpg

Hope this helps someone who has burned a FET and damaged their board. Post any questions about other repairs here I'll try to answer and post pics of other repairs if there are any questions.

Bench Test Video (http://www.youtube.com/watch?v=rrulkY3GVSo) (short version due to uploading from android phone)

Felix2010
2011.03.09, 07:08 PM
Wow, awesome job!:D

cosmicsoul
2011.03.09, 08:14 PM
Ive got one that all of the pads are burned up on, wonder if you could fix it. Our local fett technician said no way.

There are no pads period.

Action B
2011.03.09, 08:19 PM
Wow, awesome job!:D
Thanks, it took a lot of practice :D
Ive got one that all of the pads are burned up on, wonder if you could fix it. Our local fett technician said no way.

There are no pads period.

Wait, you mean all the pads on ONE FET are burned or ALL 4 of the FETs are missing ALL of their pads?!

If its just one FET I can probably fix it.

Since its you Jay, I'm also thinking there is a 50% chance your joking lol

cosmicsoul
2011.03.10, 02:42 PM
Just the fetts on the bottom are chard of no solder points left at all. Hey are you guys coming to the Carolina Cup?

rharris
2011.03.10, 05:38 PM
I've got an old AD board that I think is hopeless. During a race, people saw white smoke coming from my staked AD Pan car. It burnt a hole in the plastic chassis cover.

I tried putting new fets on, but no dice.

Wanna take a look?

Action B
2011.03.10, 05:42 PM
I've got an old AD board that I think is hopeless. During a race, people saw white smoke coming from my staked AD Pan car. It burnt a hole in the plastic chassis cover.

I tried putting new fets on, but no dice.

Wanna take a look?

I'd like to for sure. I have ad band module for testing I think its fm right?

KA2AEV
2011.03.10, 06:53 PM
Have you ever done a post mortum on a board like that to figure out why the FETs actually go bad?
I've heard that in certain conditions when the motor contacts short out
they take out the FETs but damage that bad has me wondering!
Mike

bermbuster
2011.03.10, 09:35 PM
Have you ever done a post mortum on a board like that to figure out why the FETs actually go bad?
I've heard that in certain conditions when the motor contacts short out
they take out the FETs but damage that bad has me wondering!
Mike

a binding drivetrain.....getting stuck on a board and trying revv your way out....using too powerful a motor. with the mr-03 (tighter layout) i have seen long screws short things as well as motor leads touching.....

Felix2010
2011.03.11, 07:22 PM
We can bring him back... We have the science... We can make him bigger... Stronger... Faster than before....:D

KA2AEV
2011.03.12, 09:25 AM
When FETs Go Bad

Film at 11

KA2AEV
2011.03.12, 09:28 AM
a binding drivetrain.....getting stuck on a board and trying revv your way out....using too powerful a motor. with the mr-03 (tighter layout) i have seen long screws short things as well as motor leads touching.....

Its really amazing how something so simple as touching two wires where
they aren't supposed to go can cause so much damage in a small DC circuit
One would never think that @6-7vdc could do so much!

Action B
2011.03.15, 06:26 PM
Have you ever done a post mortum on a board like that to figure out why the FETs actually go bad?
I've heard that in certain conditions when the motor contacts short out
they take out the FETs but damage that bad has me wondering!
Mike

Yes and no. I often have a hint at to what happened but I'm not certain. In the case of this board, there was solder between two circuits that there shouldn't be, however, since the FETs were removed I can't say that it was like that before or if it happened during the FET removal.

VIDEO OF BENCH TEST POSTED AT BOTTOM OF ORIGINAL POST.

SaiTam
2011.03.18, 07:32 PM
This is a board from a local racer. I wonder how I can fix this:

http://i9.photobucket.com/albums/a65/dealerxing/Mini-z/SAM_1332.jpg

civilian
2011.06.14, 04:36 PM
This is a board from a local racer. I wonder how I can fix this:

http://i9.photobucket.com/albums/a65/dealerxing/Mini-z/SAM_1332.jpg

see those holes?
use some stock motor wires, stick into it and apply solder on surface.
try to make it as flat as possible.
then find a non ripped off pcb, just direct the board to lights so you can see thru.
copy the missing line exactly by marking the wires [put note with some pen on paper].
i have many problem like those here, after spend many patient and watery eye, the problem's solved.

ps:
better if you have magnifier
and i hope u understand my english.

civilian
2011.06.14, 04:38 PM
i just notice there's missing line too near pairing button...
takeoff the button 1st.
those areas near button are really pain in the asset!

vincentimes
2011.11.12, 10:07 AM
Hello!
I have a board to damage. I want to redo track(runway) to tear away(extract).
Can you say to me where I have to recover to redo the contact?
PICTURE (http://mini-zracer.com/forums/showthread.php?p=423943#post423943)
My english is very bad, i'm frenchiiiiii sorry!
thank you!

Action B
2011.11.12, 10:36 AM
i just notice there's missing line too near pairing button...
takeoff the button 1st.
those areas near button are really pain in the asset!

Ah yes the button pad lift. I would jumper wire from the other side of the board probably on the FET underneath it. Let me know if you need to know which leg. You could try lifting off the button and extending the trace over but it would be harder to do I think, however, it would look cleaner.

tudor_47
2012.01.16, 07:41 AM
A friend of mine has by accident fried the FET's for the steering(?) on the MR03 board :R-141901B ,KO PROPO
the fets are circled in red in attached picture.

Do you know if it is possible to get replacements circuits and what are they called.

z3zinho
2012.01.16, 10:59 AM
http://mini-zracer.com/forums/showthread.php?t=36716 :rolleyes:

Be careful when removing the old fet's. I've had some pads lifting because they are so small.

tudor_47
2012.01.17, 01:13 AM
http://mini-zracer.com/forums/showthread.php?t=36716 :rolleyes:

Be careful when removing the old fet's. I've had some pads lifting because they are so small.

Thanks!
I totally missed that thread!