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xmodcanuck
2014.03.12, 02:44 AM
I got this chassis used quite a while ago. It always ran great so I never took it apart to really check it out. I noticed recently that it had a few stripped screw holes so I am in the process of switching it to a new sp chassis.
And I see that there are no fets on the top of the board. Clearly this hasn't affected the operation of the board but I'm wondering what those fets do and why would you want to remove them? (It has 6 fets (2x3) on the bottom.) To those that know more than me about this, while I have it apart is there any benefit to getting fets put on the top?

http://i474.photobucket.com/albums/rr109/xmodcanuck/ForSale/20140309_153242_zpsafccff8f.jpg (http://s474.photobucket.com/user/xmodcanuck/media/ForSale/20140309_153242_zpsafccff8f.jpg.html)

TheSteve
2014.03.12, 02:50 AM
That is just weird. I can't tell from the pic, do the pads look damaged at all?

xmodcanuck
2014.03.12, 03:40 AM
That is just weird. I can't tell from the pic, do the pads look damaged at all?

I'm going to go with...no, the pads don't look damaged. I think...maybe.
Since I'm not a solderer I'm not entirely sure, I'll bring it with me on Sunday.

byebye
2014.03.12, 05:59 AM
Previous generations had a single pair on top. The next generation had a pair on top and a pair on bottom essentially giving you a 2x2 fet upgrade. Rather than modify the chassis they modified the boards placing them on top and bottom.

There is probably a much more technical answer but that is the gist of it. Every evolution of the mini-z has been in response to aftermarket ideas I.e. FET upgrades, disk dampers, midmounts, a-arm, dws etc.

LED
2014.03.12, 06:53 AM
Only the 27mhz boards had 2 fets. I think the 2.4Ghz always had 4 fets.
I believe this board was modded by the previuos owner giving it 6 fets instead of 4.
There is no problem in removing the 2 top fets because the work parrallel to the ones on the bottom.

check the fets on the bottom, what code are they?
I'm sure they will not be 3010 fets.

In short, you have a modded board and you can probably already run every motor you want so no need to put extra fets on top.

TheSteve
2014.03.12, 11:39 AM
Mounting fets on just one side when there are good pads on both is just silly. The small traces and vias in the PCB can only handle so much current, the pcb traces also offer a small but useful amount of heatsinking to the fets. Having 2 fet packages mounted on the top and two on the bottom is likely more efficient at the end of the day then 6 fets all stacked on one side.

We could slam some fets on the other side of the board if you want Dave, if the board is working though I wouldn't worry about it too much.

imxlr8ed
2014.03.12, 01:06 PM
Maybe the stacks were already made up and instead of keeping the stockers on top, the guy just popped them off and added his stacks to the bottom (only side they'd fit).

At least it's fetted! :D

LED
2014.03.12, 01:24 PM
Mounting fets on just one side when there are good pads on both is just silly. The small traces and vias in the PCB can only handle so much current, the pcb traces also offer a small but useful amount of heatsinking to the fets. Having 2 fet packages mounted on the top and two on the bottom is likely more efficient at the end of the day then 6 fets all stacked on one side.

We could slam some fets on the other side of the board if you want Dave, if the board is working though I wouldn't worry about it too much.

Well that depends on how the bottom looks. if he put enough solder on there to make direct contact to the terminals the traces wouldn't suffer that much.
I also think the wires you see on this pic are thicker then stock, also fo the switch wich are normaly black. So maybe he moved the fets to the bottom to be able to use the thicker wires. I think the previous owner wanted every bit off power he could get :-)

Can you please post a pic of the bottom? I would like to see ho wit looks.

Thx

TheSteve
2014.03.12, 01:57 PM
If I had to take a guess at why someone would only put fets on the bottom I'd say it was so they have less chance of shorting the fet legs with the motor eyelets. I wouldn't do it that way myself, but then I also wouldn't ever stack that many fets.

xmodcanuck
2014.03.12, 02:38 PM
Bottom of board. They are 8858 fets, at least the top row is.

http://i474.photobucket.com/albums/rr109/xmodcanuck/ForSale/20140312_121017_zps02e9c69e.jpg (http://s474.photobucket.com/user/xmodcanuck/media/ForSale/20140312_121017_zps02e9c69e.jpg.html)

A 'leaning tower of pisa' fet stack.
http://i474.photobucket.com/albums/rr109/xmodcanuck/ForSale/20140312_121033_zpscded5119.jpg (http://s474.photobucket.com/user/xmodcanuck/media/ForSale/20140312_121033_zpscded5119.jpg.html)

LED
2014.03.12, 03:53 PM
Lol thats great :D

Anyway, I would leave it as it is :-)

Traveler
2014.03.13, 07:10 AM
Guessing the FETs were stacked at an angle to fit down in the chassis which has slanted sides, without having to modify the chassis for clearance. Looks like a very neat FET job!

byebye
2014.03.14, 05:41 AM
Lol thats great :D

Anyway, I would leave it as it is :-)

Guessing the FETs were stacked at an angle to fit down in the chassis which has slanted sides, without having to modify the chassis for clearance. Looks like a very neat FET job!

I concur. Looks pro.

imxlr8ed
2014.03.14, 07:38 AM
Leaning tower of power there.

Benefits:

Keeps the cg lower in the chassis :D

Cooler below the board than above it

Electricity likes to flow in one direction

Gives something to post about

Problems:

Only one I've ever seen is instability in collisions, if the fets are run really hard with a mod motor for a long time, it is possible for the solder to get overheated and in a collision, the may lose connection. I've had this happen once and seen it happen twice in all my years. (usually in awd chassis)

xmodcanuck
2014.03.14, 02:29 PM
In short, you have a modded board and you can probably already run every motor you want so no need to put extra fets on top.
Good thing I have it running an awesome PN70t motor.

Guessing the FETs were stacked at an angle to fit down in the chassis which has slanted sides, without having to modify the chassis for clearance. Looks like a very neat FET job!
Never thought of that, the leaning tower makes sense now.


Thanks for all the excellent and helpful info. Like I said, it always ran great so I will likely leave it the way it is, it just seemed odd that the FETs were missing. Knowing it can handle any motor I want I might even upgrade to a 50t.:eek:

cowboysir
2014.03.14, 05:05 PM
Thanks for all the excellent and helpful info. Like I said, it always ran great so I will likely leave it the way it is, it just seemed odd that the FETs were missing. Knowing it can handle any motor I want I might even upgrade to a 50t.:eek:

Easy now....you dont want to ruin our equality of equipment racing that you and I have going at the GTG's. If you join the rest of the high powered group I'll just put in something much slower and put on a body i dont' mind being "a moving speed bump".:D

xmodcanuck
2014.03.14, 05:45 PM
Easy now....you dont want to ruin our equality of equipment racing that you and I have going at the GTG's. If you join the rest of the high powered group I'll just put in something much slower and put on a body i dont' mind being "a moving speed bump".:D

It's okay because I have 3 other chassis with 70t motors. And a couple with Kyosho stock motors. I should probably get more PN70t though, I really like them.