T3 controller rebuild help

Hello everyone
I’ve researched as much as I can so far and need some more guidance
I bought another project gem that has been sitting for 2.5 years.
I know a fair share about them
Cleaned it up
Installed new batteries
Pulled out of the driveway for the maiden voyage and I made it about 3 miles and I got cone 51
51 motor controller voltage low electrical fault check voltage
After cycling key a bunch of time I limped it home to charge
Figured one of my new batteries was low on voltage
The turtle symbol was lit up but the weird thing was that my battery percentage said full.
Next day
Unplugged it off the charger and it ran fine for another two or 3 miles. And had plenty more speed. Until code 66 popped up
Doesn’t work in either direction and still pops up that same code and cycling key
Messed with it for two days and it won’t go away.
So I have to researching as much as I can it sounds like I need to replace some MOSFETs
I’ve got everything taken apart and I’m not 100% sure how to figure out exactly which one is bad but figure I should replace all of them that cause this code
So looking for some insight on how to test the MOSFETs and/or which ones I have to replace exactly on the T3 controller
Any other information would be superb. Here’s a picture of both sides of my controller
I found a post a while back showing one side and which ones to replace but unsure about the other.
Or someone wants to explain to me how to test them before I pull them apart that would be even better
Thanks again

Take it apart more - you will be able to see a line in the circuit board that separates the drive FET’ from the others. Looking down on the board where the F1/F2wires connect you can see that area is separated from the rest of the board, you should replace all the FET’s on the F1/F2 side.
From the pictures above it would be the ones with the black tabs, same on the other side but fewer.
I have never seen a controller with four FETS on one side, I have see two and three but not four, then again I have never opened a T-3.

Ok so took it apart some more. Looks like the only ones that have the black casing are the 4 on the 1 side
Maybe only 4 total on a T3?

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The two uprights are f connections. The traces connect to 4 on one side and at least 2 on the other.
Either check to find the shorted ones or replace them all.

Are you seeing the lines your taking about leaving the A1/2 wires?
Not quite sure

The one with ?, I can’t remember.
Mike says 3 one one side. Check the part numbers.
4 of 1 and 3 of another?


I would replace the ones circled in Red for sure and for good measure the two in Yellow. The third one in Yellow I am not sure about. It is stratiling both sides of the board.


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One of the sides will require a plastic insulator (I think it is the side with four), I put some of both sides to be safe. They can’t be grounded against the heat sink. There may be an insulator already in place. Just a thin film to keep the FET from grounding against the heat sink.

This is my plan
Replace the 4 you circled and they are labeled Q5 Q6 Q3 Q4 part number P80NF12

Then in other side replace only 2 labeled Q1 Q2 pet number P80NF

Short is between p2 and p3.



Any suffix? They look special.

They say this
Morocco 304410 p80nf12

The side with 2 says
Morocco 305414 p80nf 12

I’m guessing they are the same except the group of 4 look to be all plastic in which I can’t find online
Maybe just install the ones I found and insulate them?

I can’t find the isolated tabs either.
The 12 sufix is 120 volts.
If you use pads under them the to-220 package should work for all.
See what Mike used. I don’t have time to look through mine yet.

With that being said
Q5 and Q6 are shorted
Other side Q2

Q5 and Q6 are in parallel. Only one may be shorted.
Clip a lead where you can bridge later, and test again.

I’m just going to replace all 6
This should be fun. Haven’t ever soldered like this before
Wish me luck

Get a good solder sucker or good sold wick, getting the old ones out and the holes clean again is the hardest part. After that it is easy peasy…

Here is what I ordered from Digikey:
PART: 497-6743-5-ND

MFG : STMicroelectronics / STP80NF12


Just ordered same stuff and some of these

Going to hit up Amazon for the soldering tools

Recommend tools from Amazon and what kind of solder?