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Blade MSR SR CP CX MCX 400 500
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How to repair burned out Blade CX 4-in-1 controller

MMcGinnis

Heliman

Kansas City, Mo - USA

What is the most expensive part on the Blade CX? If you said the 4in1 controller, you are right. I just priced one at my local hobby shop at $55.00. Well, I have some good news for you guys. At least for those of you who are adventuresome and willing to try ambitious repairs. It would also be good to have decent soldering skills.

The good news? The most common failure in this 4in1 controller (stopping the rotor from turning while throttle is applied, as in a crash where the prop hits the ground). is SUPER CHEAP to repair. How about $2.00 - $4.00. That’s what it costs me to repair mine. Let me explain.

I took my CX outside for the first time last week while it was a perfectly calm day… or so I thought. I got it in the air and was having a blast when I decided to see how high I could get her to go. I got up around 80-100 feet when it began to drift away from me. Full forward and reverse couldn’t overpower the wind up there and soon it had passed over the neighbors tree line where I would not be able to see what I was doing as I was forced to bring it down. I thought the best thing to do would to be time the decent behind the trees in my mind’s eye and give a little extra throttle just as it should be landing to cushion the impact. Upon retrieval of my baby, I noticed a burning component smell coming from under the front canopy. Upon inspection, I found a component on the 4in1 controller completely burnt and split open. I was forced to purchase a new controller for $55.00 just to be able to see what the bad component is, as my bad one was unrecognizable. I vowed if I have my way, I would never pay this outrageous price again. I opened the case on the new controller and found the part number and manufacturer of the bad component.

It turned out to be a dual N-Channel International Rectifier IRF7313 HEXFET Power MOSFET device. A search of International Rectifier’s web site found this part for under $2.00. But they had a minimum order fee of $25.00. I then found this device on www.digikey.com for around $2.00 and a minimum order charge of $5.00 (if order is under $25.00). I purchased 3 of them at about $6.00 + $5.00 min order charge + $1.78 USPS shipping for a total of about $13.00. I received it in 2 days after ordering it. Way to go USPS.

Now the hard part… replacing a surface mount component with only a pencil soldering iron. This component has only 8 pins. I opened the controller case and popped the board out. It’s a little tough to get out as there is a double sided sticky piece of foam rubber in there, holding it together. Removing the old part was easy; just apply the hot iron to the pins while lifting the part off the board with the blade of a pocket knife. I cleaned up the pads as best I could when I noticed a couple of things. I discovered that the pc board solder pads were laid out in an interesting way. If you refer to the attached picture of this PC board, you’ll notice the culprit component located in the lower left corner of the board, right next to the rotor motor connector. The 4 pin pads located closest to the motor connector are actually just 2 extra wide pads. Each pad is soldered to the two left and the two right pins of the MOSFET device respectively. This fact makes soldering such a small component much easier, because if you create a normally unwanted solder bridge between these pairs of pins, it actually improves the solder joint and improves current flow capability. The pads on the opposite side of the MOSFET device are laid out from top left to top right as follows: 1 thin pad, 1 wide pad, 1 thin pad, 1 wide pad. The wide pads are required to handle the high current flow while the thin pads are for the low current control signal to the device. I discovered that the bad part had overheated so badly that one if the solder pads on the pc board had completely burned and broke off. It was the third pad from the left (thin) on my board that was burned off. I mention the dimensions of these pads because since we are working with a very small device, and most likely, your board will be burnt, it might be difficult to align your new device on the board to prepare for soldering. What you need to do is first put a tiny bit of solder on each pad, NOT the pins. Now orient the new device so that the dot on the device (upper right corner of device) is on the opposite side from the motor connector and closest to the edge of the board. Then put a drop of CA glue on the back of the device, and using a pair of tweezers, align the two thin pads with their respective device pins. If you try to align the wide pads/pins, you run the risk of the thin pads/pins not lining up. Once the glue dries, touch your soldering iron to the two dual pads and their respective pairs of pins (motor connector side of device.). Hopefully, you placed enough solder on the pads earlier to allow the solder to melt and create a good joint. I would recommend adding a little extra solder ONLY on these two dual pads/pins to create a solder ‘bridge’ between the pair of pins to improve the quality of the joint and improve current flow. Now the hard part: Heat each pin in the other side respectively to solder each pin to its pad. As long as you have a good hot iron, you should only need to touch each pin for a second to solder the joint. This little MOSFET device is VERY rugged and can handle a lot of heat, but don’t push it. If you find the need to add a little more solder to each pin, be VERY careful NOT to bridge any pins or pads together. If all goes well, you’re done. Connect a battery, the servos and motor wires up and test it out.

Now I mentioned that one of the pads on my board had burned off. If you study the attached picture closely, you notice something white obscuring the upper right corner of the MOSFET device. Since I had no trace to solder to, I took a tiny piece of wire that I soldered directly to pin 2 on the MOSFET and jumpered over to one side of a surface mount capacitor, basically creating my own board trace to replace the bad one.

While you’re operating so deep inside your beloved CX, might I recommend that you do what I did and cut slots in the case of your 4in1 to improve airflow/cooling. Also, you may have noticed that I have added a micro switch inline with one of my battery leads to create a main power switch. I then CA’ed the switch to the top of the 4in1 case where it sticks up out of the hole I cut in the front canopy to improve air flow into the motors and the 4in1. I am always annoyed with having to fiddle with the battery terminals, and I find this a nice touch for rebooting the gyro and for momentary power downs.

I have not done this yet, but I am looking for a couple of surface mount or otherwise miniature ~5amp fuses to solder inline with the motor leads to protect this MOSFET from being fried again. It would be MUCH easier to replace the fuse than to replace the MOSFET again. Besides, this board can only take so much heat before you have nothing left to solder to. When I find the appropriate fuses and complete the next surgery, I’ll fill everybody in on how to do it.

I hope someone finds this info useful.

Matthew McGinnis

04-20-2006 Over year old.
avator

Veteran

New Jersey

Good job Matt,

A trick that I use when soldering very small components with a regular solderng iron is to strap a solid piece of small diameter copper wire to the tip of the iron that extends past the iron tip by half an inch or so. I file a chisel point on the end of the piece of copper and use it for the soldering tip. I use solid mechanics wire to strap it on by wrapping the mechanics wire around the copper wire and the iron tip and then twisting with pliers until it is tight.

04-20-2006 Over year old.
MMcGinnis

Heliman

Kansas City, Mo - USA

Sounds like a good idea... extending the soldering iron tip with a piece of copper wire. I'll give it a shot sometime. Generally, I find if I place tiny bit of solder on each pad before gluing the component in place, then just heat each pin for a moment, it solders itself. Luckily, the component in question actually has a WIDE pin spacing compared to most surface mount chips, making contacting only one pin at a time easier.

04-23-2006 Over year old.
MMcGinnis

Heliman

Kansas City, Mo - USA

CX 4-in-1 repair / Fuse motor leads

Glad to hear my info helped you. I would be very interested in your calculations. Here are my measurements/calculations:

The average flight time on an 800mAh battery is 10 minutes. That is the equivalent of 4800 mAh or 4.8 Amps running amps over an hours time. Since the two motors pull 99% of the current, we can assume that each of the two motors pull half that or 2.4 Amps each while running. I measured about 3.8 volts across each motor at hover and 4.65 volts near maximum power. Using an average of 4 volts:

Current * volts = power or 2.4A * 4V = 9.6 watts for each motor while flying.

I measured between .5 -1.0 ohms across the motor windings depending at what point in the motors rotation I measured (If brushes were contacting two windings at once, I measured .5 ohm, if 1 winding was contacting, I measured 1 ohm.). This means that the current could approach 8 Amps (4 volts / .5 Ohms) each or 16 Amps through the dual HEXFET, Which BTW is only rated at 6.5 total constant amps. That would be closer to 64 watts (16 Amps * 4 volts) dissipated by the HEXFET under the worst case (2 windings in contact with the brushes). Your calculations of 26.4 watts radiated by the HEXFET seems real close to mine if you were calculating only one winding being touched by the brushes at the time of rotor stall (I calculated 32 watts). BTW if this HEXFET radiates 64 watts, at the size of .15 inch by .19 inch, if this device were 1 square inch, it would be radiating 2240 watts---quite toasty I must say.

I originally installed 3 amp inline fuses with my motors, expecting them to blow easily. I did get one of the fuses to fail after pushing three 800 mAh batteries through my CX with moderate flight. (I'm not that good yet to be aggressive). Half way through the third battery, for no apparent reason, the CX began a not so graceful pirouette to the basement floor. The upper blade motor fuse had failed. I've since replaced them with 4 Amp fuses and have yet to blow one. I have not intentionally stalled the blades to see which will go first, the HEXFET or the fuse, but I do feel confident, however, that the fuse will work. If I ever get into a crash and stall the blade, I'll let everyone know the outcome.

FYI, the fuse I am using is a LittleFuse 4 Amp PICO fuse PN# 0251004

Here is the web page for the fuse:

http://www.littlefuse.com/cgi-bin/r...SION=mBiUUxCNx4


I simply soldered the fuses inline with one lead on each motor. Careful not to allow too much heat from your soldering iron to reach the fuse core, at it may weaken or blow the fuse before you even get off the ground. I left a long amount of lead on each end of the fuse to help in isolating the iron’s heat from the fuse. These fuses are TINY, about the size of a 1/8 or ¼ watt resistor.

Another alternative, is to install the fuse holder (as seen in the web page above) inline with the motor leads. Then, when the fuse blows, just pull out the old fuse and replace it. I opted against this, as I didn’t see the need to add the extra weight, though nominal.


-----"bolo_invictus @ Radio Control Zone" Date: 08/20/2006 04:13PM
Subject: Blade CX


This is the message:

Thank you!!!! Your thread dated last April titled: "How to repair a blown 4-in-1 Blade CX controller" really helped. I have never seen a part get so hot that it unsoldered itself from the PC board as mine did. I could not identify the IOR part number from the charred remains. I've since traced out the controller circuit and made some measurements of the locked rotor current and voltage for one of the motors. The moment both rotors lock, the pass element dissipates 26.4 W!! No amount of ventillation will prevent the part from incinerating. I'll email you the details. I'd like to hear if your fuse idea worked.

thanks,

brian connolly

08-21-2006 Over year old.
avator

Veteran

New Jersey

Hey MMcGinnis,

This is a great post. Excellent information. This is what the hobby is all about.

08-21-2006 Over year old.
stickyfox

Key Veteran

Troy, NY, US

Since you are going to replace the FETs anyway, you can just cut the leads off with a knife or a small clipper and remove the package before desoldering the leads. This makes it a lot easier.

Couple other thoughts: don't breathe burning CA fumes. And I don't know if it was already mentioned but for anyone who tries this, make sure you note the orientation of the FETs before you pull them. You'd be surprised how easy it is to overlook that.

McG: You will really impress me if you can find a source for the murata gyro. I've been looking for them for a while.

-fox

08-21-2006 Over year old.
HOMEPAGE  
beefcake

Senior Heliman

Racine,WI

So which MOSFET controls which motor?

I have a 4-in-1 that give me no control over the TR. It just runs at top speed. I cracked into it yesterday after reading this article.

I was wondering if anyone knows which Transistor is the one to replace? I assume that 1 controls the main rotors, and one controls the tail rotors. Also, has anyone tried to test them, ie neither have any burn mark damage, what about testing the continuity etc of the pins.

Thanks
-CaKe

08-23-2006 Over year old.
stickyfox

Key Veteran

Troy, NY, US

There are two FETs side by side, and one off by itself. The pair is for the main motor, and the other one is for the tail. Sometimes they blow apart, sometimes they just quit. There are no gate drivers on the board, so the only other part that can fail is the MCU. If you have a logic probe, you can check the output pin for the tail rotor (pin 14 I think).

-fox

08-23-2006 Over year old.
HOMEPAGE  
beefcake

Senior Heliman

Racine,WI

different version...

So I was trying to figure out which component on my 4-in-1 was bad, I did the heat up test, which turned into a SMOKE test. Again, the TR runs at full bore (or at least it did...)

it looks like an 8 pin IC chip was the culprit. It was on the reverse side of the ESC board, opposite on of the pots. It is adjactent to a blank pad for the same size IC, noted Q1.It has identifiers as follows:

I<>R 451H
K10R
(fried line) not readable. I am kicking myself for not noting the components or at least taking a digital pic (before, not after!).

Any ideas???

Thanks
-CaKe

08-30-2006 Over year old.
stickyfox

Key Veteran

Troy, NY, US

MMG's photos are of the CX; it's got two main motors and no tail, and apparently uses different FETs.

Your fried chip is the tail FET. It's an IOR 7413; same as the other two on the bottom (the pair for the main motor). Q1 is probably a vestige of a previous revision. If you didn't find it rattling around loose in the 4/1 case, it was probably never there. The new ones only have a single FET for the tail.

-fox

08-31-2006 Over year old.
HOMEPAGE  
beefcake

Senior Heliman

Racine,WI

DOE!

I assumed the CX and CP 4 in 1 were one and the same. I kept wondering why my xtall was 90 degrees off! At least they share SOME components!

I am placing my digi-key order ASAP!

Thanks

-CaKe

08-31-2006 Over year old.
Jetset

Senior Heliman

Picton, Ontario Canada

Clarification

MMcGinnis, I think this is great! Thankyou!
I am a little confused though. I can't seem to figure out your explanation of how the solder connections should be.
Looking at you photo, do I simplay bridge the pins on the left hand side together in two pairs the bridge them to the right side?
Could i please impose on you to draw a diagram like I did to help me figure this out?
I am great at soldering, just not smart following instructions!

Thanks for any assistance!

Howzitgoin' eh? Goin' fast in the "Great White North"

09-28-2006 Over year old.
HOMEPAGE  
stickyfox

Key Veteran

Troy, NY, US

That doesn't look right.

I don't have the datasheet in front of me, but going from memory, in your illustration I believe the top pin on the right side should be alone, the bottom three on the right side can be bridged, and the four on the left side can be bridged. You definitely don't want to bridge across the top.

You can look at the lands for Q1 in the photo above for a hint.

However, it really does not make a difference whether you bridge the pins with solder. Solder has only one tenth the electrical conductivity of the lead material. Very little current will flow through it, which is actually a good thing because you don't want it heating up. The only advantage to bridging the leads is that if you have a big soldering iron and do it accidentally you don't have to clean it up.

-fox

09-28-2006 Over year old.
HOMEPAGE  
Jetset

Senior Heliman

Picton, Ontario Canada

Does this look correct?

Just to clarify...how about this?http://runryder.com/photocache.htm?...pg&target=photo
http://runryder.com/photocache.htm?...pg&target=photo

Howzitgoin' eh? Goin' fast in the "Great White North"

09-29-2006 Over year old.
HOMEPAGE  
Jetset

Senior Heliman

Picton, Ontario Canada

Like this

Does this look correct?
Bridging is not a problem, making sure I get this correct is. :)

Man, I don;t know why i have such a hard time inserting pictures! :) DOH!

09-29-2006 Over year old.
HOMEPAGE  
stickyfox

Key Veteran

Troy, NY, US

I checked on the data sheet; your most recent pic is correct.

-fox

09-29-2006 Over year old.
HOMEPAGE  
Jetset

Senior Heliman

Picton, Ontario Canada

Cool!

Thanks Fox, I can now go ahead and fix my CX.
Thanks for the help!

Myles

Howzitgoin' eh? Goin' fast in the "Great White North"

09-30-2006 Over year old.
HOMEPAGE  
johndog35

Senior Heliman

Kansas City, Kansas

Here is a diagram I made in AutoCad. I have it in a .PDF picture. Its copied from my Blade CP 4 n 1. Lets make it a little easier to read.
I tried to upload it but it keeps coming up with picture from anoter post. It you want it know where you want it sent. It has all the numbers and design just as it looks on the board.

10-11-2006 Over year old.
johndog35

Senior Heliman

Kansas City, Kansas

Here is that diagram and maybe better grammer.

Landings are nothing more than controled crashes

10-11-2006 Over year old.
Jetset

Senior Heliman

Picton, Ontario Canada

CX

Hi johndog,
Thanks for the picture but it's kind of hard to see.
Myles

Howzitgoin' eh? Goin' fast in the "Great White North"

10-11-2006 Over year old.
HOMEPAGE  
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How to repair burned out Blade CX 4-in-1 controller

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