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I've got FETs in my SE!

Posted: Thu Sep 25, 2003 10:09 pm
by crazydave
A member at TRC, slider69, had some misguided concepts about the function of transistors and mosfets. I was just trying to set him straight, but out of the conversation came a very, very good thing.

He discovered a couple stacked transistors on the bottom of the PCB. Since the SE is faster forwards than reverse, it made sense that was related to this.

So first I put a FET there to make sure it was compatible, and it worked. so I stacked another FET, and I definately had a noticable increase in performance. :-D

Here is the one to swap (highlighted in the picture)
Image

I'm pretty positive the one next to it is for reverse. I'm going to swap that for a FET, to help conserve battery life. That's right, my car will run longer now too. I might stack a third FET, to see if that does much more for speed.

If you got the soldering skills, this should be your number one, 'must do' mod for your SE!!

Posted: Thu Sep 25, 2003 10:13 pm
by VooDooMafia
nice dave keep us posted on the 3rd stack

Posted: Thu Sep 25, 2003 10:14 pm
by Yugo DSC Maxxer
Whoa!
I want that for my brand-spanking-new SE!
(I got it yesterday!!
Yay!) :-D

Posted: Thu Sep 25, 2003 10:30 pm
by CaboWabo
tell me when to ship my SE to you for the modding lol

Posted: Thu Sep 25, 2003 10:39 pm
by crazydave
CaboWabo wrote:tell me when to ship my SE to you for the modding lol
I can't tell you when, but ya better hurry, my supply of FETs is going fast!

These things are like drugs, I can't get enough of them! :lol:

Posted: Thu Sep 25, 2003 11:05 pm
by VooDooMafia
crazydave wrote:
CaboWabo wrote:tell me when to ship my SE to you for the modding lol
I can't tell you when, but ya better hurry, my supply of FETs is going fast!

These things are like drugs, I can't get enough of them! :lol:


There only going fast cause you out on the cornner hustling them off.

I say you out there turning thems crack heads into fetheads.........

Posted: Thu Sep 25, 2003 11:08 pm
by Yugo DSC Maxxer
Dude I want mine modded!
But, I can't ship anything until we move...Grrrr...
Stupid divorce! My parents just had to do it now, didn't they!
:x

Posted: Fri Sep 26, 2003 12:44 am
by payaso
Thanks God... I knew it wouldn't be long before you got the SE problems under control..


Keep us posted dude.


silla :D

Posted: Fri Sep 26, 2003 6:24 pm
by ph2t
Some very interesting work there Dave. I thought the pcb was covered in a black epoxy resin type thing from what I've seen in some pics. Must be only the top end.

I guess now with the dive into proportionality the traditional H bridge has been replaced for a ESC? Can you still see four transistors in the same area? This is interesting. Also notice the extra blob of ceramic die on the pcb. Looks like there is two IC's on the pcb doing stuff now.... hmmm...... :???:


ph2t.

Posted: Fri Sep 26, 2003 9:49 pm
by crazydave
ph2t wrote:I guess now with the dive into proportionality the traditional H bridge has been replaced for a ESC? Can you still see four transistors in the same area? This is interesting. Also notice the extra blob of ceramic die on the pcb. Looks like there is two IC's on the pcb doing stuff now.... hmmm...... :???: .
You noticed what I noticed tonight. I noticed the power splits into 2, and are essentially powering 2 separate systems. So it would seem that would be the reason for the short run times.

After examining the area closer, there is an H-bridge on the output section, but no PNP transistors are used, the others are instead flipped.

I replace the one next to the ones that were stacked, and it improved reverse. I tried doing the other foward one, but got no more increase from forwards. So I tried triple stacking he one that was double stacked, and again I was unable to get any gain in performance. So the best you can do with these cars, is replace the 2 double stacked ones with FETs, and maybe double stack the reverse ones to even things out.

The improvement is not nearly as drastic as a mosfet modded bit. You could say it's only bringing it to the level of performance of the original Zip Zap (I still have to compare), but it proportional, and it's powerful enough to pull a 4.2 now, and that's more than fast enough for serious racing.

Posted: Fri Sep 26, 2003 9:52 pm
by hogjowlz
crazydave = bit guru

Posted: Fri Sep 26, 2003 9:59 pm
by sessiz
hogjowlz wrote:crazydave = zip guru


Excellent work dave. :-)

Posted: Sat Sep 27, 2003 7:07 am
by maximan
dave
aren't zip zaps se 2.4 volts?
so wouldn't you have to do a special fet mod?

Posted: Sat Sep 27, 2003 9:16 am
by crazydave
Thnaks guys. :-)

Maximan, these mosfets are rated for up to 20v.

Posted: Sat Sep 27, 2003 10:43 am
by CaboWabo
actually, crazydaves the bitNinja according to his rank now lol
bitGuru comes later after more posts lol (though he deserves it now)