"Franken-Spedix" Build Log, Mods and FC Conversion Tutorial (w/ pics)


New member
So, this is going to be a pretty in-depth thread about the Spedix s250 quad, and what I've gathered from my own experiences, what it is now, and plans for what I'll be doing next. I'll do my best to separate it into sections with headers, as it may end up being kind of lengthy. I'll include any and all info on the topics I'll go over, including unexpected problems I ran into, what you should expect, and if you are one of those who has one, maybe it can give you some guidance if you are unsure, or maybe even give you some ideas. I'll post this at the end as well, but if you end up having any questions, comments, opinions, or money :)p) I will gladly accept all of it, and do my best to get back to you ASAP. I didn't see very many resources or builds other than typical reviews, and I like to see a little bit of a variety once in awhile, so this is for anyone that it may apply to.

What I thought was going to a be simple flight controller and PDB swap turned into a minor headache. First of all, I love this quad. It has flown great so far, and have flown almost 30 flights with hardly any issues at all, except for the "overly-basic" and limited tuneability of the KK2 in comparison to configuring CC3D with the OpenFlight software suite. I've managed to film a handful of videos, put some on YouTube for some friends, and it's just all around been a lot of fun so far, especially after getting into FPV. This was my first 250 class quad, as I've flown the crap out of the smaller ones, but was a whole different ballgame compared to the Nano QX and Inductrix that I flew around the house (and still do). Eventually I found that there was a handful of things that seemed to be kind of annoying with my setup, and I have thought of ways to improve on it, without sacrificing an arm and a leg or forking up another chunk of cash for another entire model. I'm definitely not rich, but not cheap! If that makes sense, or if it's even possible. Who knows.

To start off, I picked this quad up secondhand, as one of my buddies had originally picked it up from a local hobby shop near us, and lost interest after about a few weeks. It was a BNF version, and I'm not sure why, but apparently it was not exactly the same design as the ARF versions. Not only that, but the option of either a KK2 or a CC3D flight controller makes a total of FOUR different layouts...maybe more if you count the agility frame, Hexacopter frame. Basically everything but the upper and lower frame pieces are the same Sure that only seems obvious, but there were some big differences that weren't as obvious as I would have thought.

Things like the same esc's being used across all models, but some coming with different wiring...different versions of CC3D controllers in both kits and replacement parts on the shelf, some motors with bullet connectors and some that were soldered to the esc...Maybe it was just put together differently as a RTF kit, vs someone buying the ARF solderless "lego" kit. Not bashing anyone's reasoning for buying one, but why assemble it differently, if the end result means the parts will be different, and might I add, original spare parts for the RTF kit not even being available...I mean it's just complicating things, especially for those who might crash it, try to rebuild it, to find out everything was soldered together with wires jammed in bad spots, and no support or resources online. With so many unnecessary variations I can understand why there's only a handful of videos that go into great detail, like Buddy RC. All that being said, the diversity of what kind of 250-300 class multirotor you can get from Spedix is great. Quality is probably solid medium, given some people's motor bells literally flying off of the SunnySky 2204/2300kv motors (NOT 100% Spedix's fault I guess...but at the end of the day, quality control falls on the last person to inspect parts they sell), but the differences in the assembly of the ARF to BNF versions is pretty unnecessary.
So that being said, The BNF is what i had to work with, and I just felt compelled to do a nice in-depth overview on everything in case there's anyone that thinks they might be SOL. Don't worry, you're not!

BNF versions came with a carbon fiber bottom frame plate with a PDB circuit built into it, and had a matte-like finish on the surface, which was similar to the carbon top frame plate. ESC's were connected by white plastic 3-pin connectors on the PDB, and the flight controller of choice had downward-facing pins for the sets of motor outputs, so it popped right on top of the PDB nice and clean:

View attachment 58970
BNF s250 Bottom Frame Plate w/ Built-In PDB

ARF versions came with the typical glossy carbon frame plates, and also came with a separate compact PDB, which either flight controller was mounted on, preferably with either double sided tape... or for a more solid foundation, (and probably more accurate sensor readings) meant going out and buying yourself more standoffs and screws. However, there were no longer those dumb white connectors for the esc's anymore, and instead, you had inputs for a a set of TWO 2mm gold bullet connectors from each esc, for a total of SIX...Which means they used this standalone PDB for the Hex model they released later on...but eventually there came to be a REVISION to this board (NOT THE ONE PICTURED, ran out of data for pics look at my quad as a point of reference, later in the thread), and none of the support was updated to emphasize it! SWEET. The revised version of the board (which I recently installed) now has separate cables and sets of pins for supplying power to auxiliary components or FPV gear, whereas the first board had it soldered on, they changed the orientation of the battery leads with the Deans connector pre-installed, so that instead of being connected on the side, it feeds through the hole in the back so that you can connect it from the back. Giggity.

View attachment 58972
1st version of the ARF s250's PDB

View attachment 58971
Revised PDB

...I wanted a smaller PDB for mine anyways...when my buddy crashed it before I took it off his hands, he apparently flew it into a tree and busted the bottom pdb plate. Interestingly enough, it didn't damage the PDB circuit. It still worked perfectly fine, and still had "most" of the important mounting holes so it could line up...which were the same mounting points as the stardard carbon lower frame plate (hmmmm....???) So...we bought a new carbon plate, dremel'ed off the broken parts around the circuitry and made a nice carbon fiber sammich...which was "kinda" held in by zipties in the corners and this crazy 3m tape that was super strong, and had a thick gel-like adhesive for absorbing impact, which seemed pretty solid...Although, I was later wondering if having the flight controller mounted so a soft surface like that would affect the quad's "snappy-ness", and if it possibly lowered the accuracy of the sensors on the board, as compared to being more fixated directly to the fame...idk...was always a thought running through my head.

After trimming the busted edges of the original PDB

3M double-sided tape and zippy ties galore...but I flew it for about 30 flights and didn't have hardly any issues at all, except for my pet-peeves of it's aesthetic qualities...all rigged-up looking...haha

That being said, I normally prefer not to rig things up if I have the option not to...but truth be true, the struggle is real, and I didn't have an option, nor the money to do it differently! Additionally, when I really got to messing with the PIDs and autolevel settings, I had to take the dang thing apart like 3 or 4 times a day trying obtain more aggressive settings that I was comfortable with...with the positioning of that carbon fiber pdb sammich that was going on, there was no room to get your hands in and play around in the menus...especially when I later added the Mobius and FPV gear, and really wanted things dialed in better as I got more comfortable.

Last edited:


New member
So, what it seemed to be boiling down to, was that while flying with the KK2, whether I had stability either on or off, it just had way too much of a sloppy feeling to it. It was responsive, but was sloppy, and not snappy enough...even having messed with the board endlessly, writing down every number an setting before, during and after I made changes. Thus, I decided to kill a few birds with a stone, or turned out to be a minor overhaul.

ESC's and PDB: BNF vs ARF
So my new goal was to install the newer standalone PDB, and a CC3D flight controller in place of the KK2. This posed a few problems, however. On the BNF s250, we had that bottom plate PDB acting as a vessel of signals for the entire system: the ESC's plugged directly into the board, which is normal, but not with normal bullet connectors like are configured...which is what the new board uses this time around...so there's the first example of a different way of installing the same part, and only selling spares for one of the two, which ultimately won't fit what YOU may have without pretty fair modifications... unless you know what to do! But most people wouldn't gamble with the lack of information available, nor think that it would be worth the effort, compared to just going out and buying new motors and ESC's that would connect to the ARF's PDB with the bullet connectors. And I agree. But, my ship hasn't quite come in yet.

At first glance, the ESC's on the BNF look almost identical to the ones on the ARF. And they are, for the most important things which are the ESC's themselves...

EXCEPT for the fact that there are 3 wires to each white connector at the PDB on the BNF, which are WHITE, RED and Black. And they're also a pretty thick gauge, too thick to be running at least one of the 3 wires from each ESC to their corresponding motor output pin on the Flight Controller... and what we actually NEED, are the 3-pin pigtail harnesses with the female connectors, with a much smaller gauge of wire...but its actually how the esc's come on the ARF kit?!?! Guess what, those are the only replacements, and if yours have a problem, this is exactly what you get to do. SO...where would the fourth wire come from on the BNF ESC's? What do you do? Exactly this:

With the landing foot and small plate with 3 allen screws removed, you can remove the ESC, and inspect the wires and their solder joints. What's interesting is the unused GROUND (-) contact next to the WHITE signal wire. Ta-da...that's where that GROUND wire would normally come from. The SIGNAL wire is where the white wire is currently soldered. We need both of these in order for the Flight Controller to send signals to the ESC's, which in turn will translate this to an Alternating Current (AC) in order for our brushless motors to work properly...So that's basically how that system works long story short, in case you didn't know.

NOW what we need to do, is de-solder the white wire off of it's contact, and make our own pigtail harnesses for each ESC, so they can connect to their respective sets of pins on our Flight Controller. I re-purposed 4 identical 3-pin servo leads from a scrap box (BROWN, RED, and ORANGE: in that order) cut the female connectors off, pushed out the pins in the middle of the male end, and removed the RED wires and their pins altogether giving us a GROUND wire (BROWN), an empty space where a +5v POWER (RED) wire used to be, and our SIGNAL (ORANGE) wire at the opposite end.

Strip the two ends, and you do NOT need much core exposed to solder it, as if your iron is hot, these small wires will still solder fine, but we need to watch out for the other components, and how close our two solder contacts are to each other on the ESC...which is why we need to be especially careful here...

DO NOT to add too much solder, or risk shorting
DO NOT have your iron too hot and risk burning the board or other components
DO NOT put the wrong wire on the wrong solder pads. Write things down to remember and stay oriented, if you have to.

When you're done, it should look similar to this:

Next, strip the larger BLACK and RED wires that are sort of braided together, grab yourself some male gold 2mm bullet connectors, slide heat sink over the wires (or not...the bullet connectors are forgiving and allow you to just slide it over when done soldering), and solder them to the wires, make sure your connections are nice and strong!

Double check while you have the chance, and when you have an arm done, it should look similar to this:

Move on until you finish the other three arms.

Your SPEDIX PDB should have come with a small cable, which is for a stepped-down regulated +12v Output that you could power your FPV gear from, if you're running a 4s LiPo and don't want to fry your FPV gear. If you don't need it, leave it open. I use a 2-4s balance port filter velcro'ed underneath my upper frame plate, and plug in the balance port connector from my main LiPo flight battery, and don't run much else, so I won't need to worry about toasting anything, nor do I worry about getting all the way underneath that PDB again...because once you tighten it down, it'll be a lot harder to get to later. And quite frankly, I'd like to not have to take this thing apart for awhile after I have finished!

Then, (considering you have the NEWEST PDB like mine) with the the battery cable fished through a hole in the lower frome plate and running out rearwards, and the red "SPEDIX" plate (heat sink? IDK) facing DOWN, connect your 2mm gold bullet connectors to your PDB, running the wires from each arm to the corner of the board closest to it. For a Quadcopter, we're leaving the center sets of bullet connectors OPEN, and if it's oriented correctly, your #1 motor (ESC) wires should be connected to ESC1, as printed over the corresponding pairs on the board.

Luckily, I now have experience with both the KK2 and the CC3D, and I can tell you that the motor numbering and the pin orientation is the same, and I tried to explain it a little easier in a picture which labels the direction the pin numbering, what "what-goes-where", what each motors' respective number and ORDER (ex: Inside diagrams of OPENFLIGHT, motors have a sequential order as I labeled on the props... from #1-FrontLeft-CCW, #2-FrontRight-CW, #3-RearRight-CCW, #4-RearLeft-CW, in a clockwise fashion...and try not to get confused, as I listed the motor directions as well, but everything will be in a picture where they are labeled.

The pigtails we just made will connect to to the CC3D Motor Output pins, numbering output channels #1-6 going from the FURTHEST RIGHT vertical set (3) of pins, to the Furthest Left Set, being set #6.

If you're looking straight at a vertical set of pins lets say, for example #1, (Furthest Right) connect your 2-wire cable, making sure (from the TOP_DOWN, IN THIS ORDER, assuming the board is mounted flat in the quad:

SIGNAL is on top
nothing in the middle
GROUND on the bottom

Connect all of your other pins, make sure the same colors are all on the same as the pins next to them in the same row.

The motor output pins should be faced at the Rear of the quad, and if you have the same Genuine "SPEDIX" branded CC3D board as I do (Some versions have offset pin orientation relative to where the board will think the nose of the copter is, so make sure you check your Hardware Version, and have it orientated correctly or it WILL NOT fly right!

Only other thing is to connect your DSM2/DSMX satellite to the 3-pin port facing the front of the quad, pointing at the plastic FPV mount. I just took a semi-thin strong double sided tape, and made sure that the CC3D was centered inside of the PDB and Quad, and would absolutely not move...thinking that having too much of that 3M gel type double sided tape may have caused it to drift a little over time, causing a slight error in sensor accuracy...so I wanted to minimize that chance this time around, just to be safe. After that's all mounted, I just took my Satellite RX and sammiched it right on top of the CC3D with double-sided tape again.


One last final picture of everything labeled, as a point of reference:

Bind your RX to your radio TX, set up everything by watching Wes from Buddy RC in this YouTube video: (I'd explain more, but I did this thread all in oneshot (pun) and my hands KILL. haha

After you're all set up, you should have a glorifying little moment like this:

And the Franken-Spedix LIVES.

Hopefully this helps anyone along the road...If not, hopefully it succeeded as someone's morning toilet read before they run to the hobby store!

Also, as I said at the beginning, If you have any questions comments etc, let me know and I'll get back to you ASAP.
Thanks and Good Luck!
Last edited:


New member
I might just keep adding to this as I go on, I'm going to take it out for a fly and see how it does, but later today I will also be picking up some some Velotech Magic 16A OneShot ESC's...~10 bucks/ea. on a Cyber Monday sale from Buddy RC, so I jumped...my plan was originally going to be adding those ESC's so I could safely run my HQ 5x4.5 Bullnose props. I was reading up and watching some performance tests, and wasn't sure the 12A SimonK's could handle the current from those props, especially if I run a 4S later on.

I may wait a little bit, but I'm also interested in how much those OneShot ESC's can improve the feel and "snappiness" in Acro mode...I've heard pretty good things so far, but want to see how things will perform over the KK2 version in comparison...one thing I tried to research myself, not a lot of detailed comparisons between the two boards on the same quad...that may be the next video I put up once everything is dialed in good.


All of your photo attachments seem bad. Did they not upload?

Personally, I use flickr. There is a button to copy BB code. But that's personal prefrence.


New member
All of your photo attachments seem bad. Did they not upload?

Personally, I use flickr. There is a button to copy BB code. But that's personal prefrence.


No idea what went wrong, but I went through and re-uploaded them from photobucket and looks like they're fixed :D

Should be a little less boring now. haha


New member
Still stuck inside due to the crappy weather and haven't had the maiden with the CC3D :(

However I tried to be a little productive and installed some LED's I had laying around. Should be pretty cool for night fly's at our field or in the dome (same one the Horizon Indoor Electric Festival is at, every other Saturday night).

Soldered the leads and made a 3 pin input connector on one end, and ran it to the 12v regulated output on the PDB. Could've made it so I could use my radio to control it, but just figured it wouldn't hurt much to just have them on all the time.



Junior Member
So glad to see this has been successfully done, just wish I had seen this before I picked me up a big pooper BNF s250 too! Just wanted to say thanks for posting up all ur photos and advice! Looks like I'll be placing an order for a carbon bottom plate, PDB, and wait... CC3D is now out of stock too!! Nooooo!!! Darn u BuddyRc!