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Old 06-06-2012, 11:48 AM   #1 (permalink)
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Default Incidence of Mini CP Receiver Damage

Right now, I have 4 Mini CP receivers sent to Walkera for repairs. In fact, I have had 5 incidences of receiver damage in 150 flights. All of this took place during the month of May. I am concerned that this is higher than either the Genius CP or MCPx. My incidents were as follows

1. Battery lead pulled off - this was fixed by my vendor
2. Main motor and tail motor servo sockets damaged following a hard crash onto concrete.
3. Blown main motor and tail motor FET. I was flying in slight rain and the receiver smoked as I tried to rebind it following a crash. The heli crashed into a puddle of water the previous day without any pronblems.
4. Another receiver was smoked when I connected the main motor from 3. to the receiver board. I checked that the motor did spin before doing so. It seems that there was some damage in the motor.
5. The receiver suddenly smoked within moments while i was hovering with a new tail. The tail had been assembled for me by a professional and it was possible that he made a mistake.

I have also had incidents of battery lead being pulled off and blown fets with the Genius CP and MCPx. However, I am a bit worried that the incidence may be higher with the Mini CP. The coil is a notorious example and so far I haven't been affected. The placement of the main motor and tail motor sockets at the front of the board is also a concern, as is the very short battery lead that is susceptible to being pulled out.

Right now, the turnover time for fixing receivers is over 4 weeks. Walkera usually fixes them for free but you have to pay for return shipping. My vendor has charged my $3.2 for each previous repair so far. I have got 2 air frames and there is no way I am going to buy another receiver.

I wonder what are others' experiences on this?
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Old 06-06-2012, 01:21 PM   #2 (permalink)
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I've blown two receiver's tail motor FETs. This was due to bad wiring going to the tail motor. There was a part of the wires that had worn off and they shorted. Other than that I had one coil come off after a crash, but was able to re-solder it on using the existing coil wire and a healthy does of Bob Smith thick CA. I of course no longer have telemetry due to that. It helps greatly if you know how to solder it yourself to fix the minor problems. I've learned how to solder because of this heli! lol

Currently sitting on two dead boards, one is being replaced by a vendor and I may send the other in for repair although Walkera didn't offer that up after our email stream for whatever reason.
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Old 06-21-2012, 11:52 AM   #3 (permalink)
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I want to post a follow up on this. My second receiver was repaired by Walkera a coupleof days ago. I found that the technician had put on the motor sockets the wrong way round. Still I am grateful that it was repaired.

To my horror, the tail fet blown suddenly today while I was flying it. I was probably at some fault here because it was slightly raining and the wires were wrapped round a 2.5mm CF rod. It was possible that the wires had been damaged by a blade strike or that the rain water shorted the tail motor.

My vendor told me the incidence of blown tail fets is very high with the Mini CP, so much so that many are now scared of flying it. Instead, they are switching to the V120D02S even though that is much less durable. He recommends that I buy a complete tail assembly each time rather than to wrap the tail motor wires around a solid CF boom.

So now, I have got 4 receivers with blown tail gets sent back to Walkera for repairs. I will update you once I get them back. I am really getting fed up with it. I have had 163 flights and a receiver had been damaged 6 times. A truly great heli has been ruined by all this. I am surprised this isn't mentioned more often here. Perhaps modelers here are much more experienced and technically minded than those in Hong Kong. For a start, Walkera helis are sold at LHS so we can get good support. Also, there is a culture of dependency over here so that people rarely buy DIY furniture or know how to fix their cars.
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Old 06-21-2012, 12:26 PM   #4 (permalink)
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I have been lucky with the RX so far. (I did kill one when a crash ripped the coil off, before I knew to glue it down.)

But, I would recommend to everyone to Double and Triple check your tail booms visually and with an ohm-meter / continuity tester for short-circuits before installing them.

I make my own tail booms en-mass... I have about 6 altogether that I keep ready to switch out in the my field box. When I get down to 1 or 2 left, I have a soldering party and switch the motors to new booms on all of them at the same time. When I finish, I am very very very careful to check for shorts... just like plugging speakers into a nice amplifier...you never want to see that smoke.

The most dangerous common spots are where the + wire enters the motor-case and where both wires enter the white plug.
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Old 06-23-2012, 07:16 PM   #5 (permalink)
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Use some other wire.... some 30g works great! That thin magnet wire is not that good. Wrapping it around the boom also a bad idea, run it up the left side so the blades do not strike it.
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Old 06-25-2012, 10:29 PM   #6 (permalink)
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Thanks for your input. I think there are a number of risky situations with the tail boom.

1. The wires damaged when you are removing the motor and wire from a damaged stock boom.
2. The wires get damaged as you thread the wire through a new boom.
3. If you wrap the wires round a solid tail boom, they could get damaged by the blades in a crash. You should use thicker wires, fix the wires on the side or underneath, and/or use shrink wrap.
4. The tail motor could be susceptible to being shorted if used in wet conditions. I think this happened to me before but this is more controversial.

Right now, I have got two air frames and cannot do anything as I have 4 receivers under repair. The problem is that if and when they are repaired, they may not fly as well as before. In any case, I am not going to buy a new receiver. I will probably use complete pre-assembled tail booms for the moment.

The Mini CP has been a very great heli to me despite the large amount of downtime. However, I have been able to have my flights with my V120D02S during this period despite the higher repair costs.

Last edited by zadaw; 06-26-2012 at 10:37 AM..
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Old 06-26-2012, 09:27 AM   #7 (permalink)
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Just for future reference, using electrical or electronic equipment in wet conditions is usually not a good idea. There's little controversy about that.

As for just using complete tail sets, that's the easiest and most reliable way to go.

I have luck working on the component level but that's just me.

The main thing is, find what works best for 'you' and the more options one has, the better.
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Old 06-26-2012, 03:27 PM   #8 (permalink)
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Heli,
Even with the complete tail sets, its a good idea to check it for shorts both visually and with a meter before using it. ( It is coming from the Walkera factory remember... )

Zadaw,
My procedure for switching the tail motors is as follows:

1. Carefully remove the heat shrink from the plug side with small wire cutters. DO NOT CUT THE WIRES!!!
2. tape the plug down to the table (I use a pyrex bowl turned upside down to solder on)
3. heat the splice joints and pull them apart (THERE IS NO NEED TO CUT THE WIRES!!! That magnetic wire is a PITA to remove insulation and tin - If you unsolder/pull apart the existing splices, you can avoid it. Pulling them apart while heated will leave the wires perfectly tinned with solder and ready to go.)
4. pull the wire out of the boom from the tail motor side
5. insert the wire into the new boom
6. apply two small pieces of heat shrink to either lead and re-solder to back to the plug. ( once again, I tape both sides to the bottom of the pyrex bowl. This makes it very easy to just kiss the joint with the iron and it will be done. Usually even, there is no need to add any more solder)
7. heat the tubing to shrink it around the exposed leads
8. check for shorts
9. check for shorts
10. check for shorts....
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Old 06-27-2012, 10:21 AM   #9 (permalink)
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Quote:
Originally Posted by ChitownMatt View Post
That magnetic wire is a PITA to remove insulation and tin
My good friend gave me two tips for removing the insulation on those type wires.

1) Use sanding paper to sand it off, make small strokes and check often to see if you made it thru.

2) Dip the wire's end into solder that is sitting on an iron's tip. Let it sit in that for awhile to burn away the insulation and tin the wire at the same time!
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Old 07-13-2012, 03:17 AM   #10 (permalink)
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that fet ic is available individually for less than 2 dollars at digikey. With some practice the entire repair won't take 20 minutes, don't sweat the small stuff.
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Old 07-22-2012, 10:46 PM   #11 (permalink)
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I want to give an update and it is not that good. I have received two receivers back from Walkera for repairs. They were both repaired free of charge although I had to a $3.2 shipping and handling fee.

1. This one had a damaged motor socket at the front that was repaired. However, the technician had put the sockets the wrong way round and I had to change. After using it a couple of days, I suddenly smoked a tail fet. I am not sure what was the cause but I found that the shrink wraps were coming off at the tail motor end.

2. This one had a blown tail fet that was repaired. It flew just as well as before and I was quite happy with it at first. However after 36 flights, it just stopped working. There seems to be something loose on the board as the board will work from time to time. However, I just could not identify the component involved. Although I have had a number of crashes, they must have been very mild since my tail boom, canopy, head and skids were completely unscathed. I did have a number of unintentional inverted blade scrapes and that may caused excessive vibration. The reason I had these scrapes was my batteries have lost much of their power after being left fully charged for some time.

So the jinx is still well and truly alive with me. I have never been able to get either of my two Mini CP airframes to work more than a few days. That is despite having 4 receivers. When the Mini CP flies, it is really great but this is completely ruining my experience with it.
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Old 07-23-2012, 07:06 PM   #12 (permalink)
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zadaw,

I know you're in Hong Kong, but see the thread I just started:

https://www.helifreak.com/showthread.php?t=437426

Not sure if it's worth it or not for you to send all your receivers to him, but I can bet he can get them all like new again, the right way.
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Old 07-23-2012, 08:04 PM   #13 (permalink)
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Quote:
Originally Posted by gabeoravitz View Post
zadaw,

I know you're in Hong Kong, but see the thread I just started:

https://www.helifreak.com/showthread.php?t=437426

Not sure if it's worth it or not for you to send all your receivers to him, but I can bet he can get them all like new again, the right way.
It is really great that someone is finally offering a repair service for Mini and Genius CP boards like the MCPx. All my boards are with Walkera again and It seems that some of the delay was with my vendor. Also, it costs less than $48 for me to get a new board here.
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Old 07-23-2012, 08:23 PM   #14 (permalink)
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I feel like I am ready to provide this service to walkera owners in the Usa at a fair price with a turnaround time an order of magnitude better than the factory.
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Old 07-23-2012, 08:41 PM   #15 (permalink)
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Quote:
Originally Posted by zzyzx View Post
I feel like I am ready to provide this service to walkera owners in the Usa at a fair price with a turnaround time an order of magnitude better than the factory.
I am sure you service will be highly appreciated. Walkera prefers to deal with vendors directly and I am not sure whether US based vendors are willing to offer this service. In any case, Wakera often refuses to repair a receiver if the work is too complicated for them. Anyway, I will point out your services to others in RCG.
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Old 07-31-2012, 04:38 PM   #16 (permalink)
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Default rx uncontrollable change of pitch

My mini started doing positive/negative pitch by itself all of the sudden. So i just zoom around and all of the sudden it goes up or down. Trying to investigate what exactly causes that, but it seems like it happens at the begginnig/ after exiting the maneuver. I was practicing figure 8 today, on the left turn couple of times it went up, going down mostly on the right turns. The swash just lifts/ lowers all by itself and there is no way to correct it. Was landing down with the throttle stick all the way to the top and rotor spinning at the max rpm. Its not a loose shaft either. After the landing/crash, if i kill the throttle, the swash levels and everything is back to normal until it happens again. There was another dude who had this problem, he says that cleaning the servo plugs solved it for some time until the problem returned. Did anyone had anything similar, any advice on how to fix it?
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Old 08-01-2012, 12:39 PM   #17 (permalink)
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Quote:
Originally Posted by Melnik View Post
My mini started doing positive/negative pitch by itself all of the sudden. So i just zoom around and all of the sudden it goes up or down. Trying to investigate what exactly causes that, but it seems like it happens at the begginnig/ after exiting the maneuver. I was practicing figure 8 today, on the left turn couple of times it went up, going down mostly on the right turns. The swash just lifts/ lowers all by itself and there is no way to correct it. Was landing down with the throttle stick all the way to the top and rotor spinning at the max rpm. Its not a loose shaft either. After the landing/crash, if i kill the throttle, the swash levels and everything is back to normal until it happens again. There was another dude who had this problem, he says that cleaning the servo plugs solved it for some time until the problem returned. Did anyone had anything similar, any advice on how to fix it?
I has happened to me with the V120D02S and it was done to poor servo connection as well. In my case, I replaced the entire servo because I didn't know how to deal with the plug. You can try to identify the servo involved by spooling up the heli after removing the blades. The affected servo should twitch badly.
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Old 08-01-2012, 02:40 PM   #18 (permalink)
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Quote:
Originally Posted by zadaw View Post
I has happened to me with the V120D02S and it was done to poor servo connection as well. In my case, I replaced the entire servo because I didn't know how to deal with the plug. You can try to identify the servo involved by spooling up the heli after removing the blades. The affected servo should twitch badly.
Cool, thanks zadaw.
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Old 08-03-2012, 05:54 AM   #19 (permalink)
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You should make sure that the board side pins are not bent or damaged. You can remove the connector from the board and plug it in for a better look. You're probably looking at the white wire for erratic operation, one of the others if weak/shutting down. Ensure a strong connection from servo out to mcu pin. A few had me chasing emi when it was vibration + a loose connector - --- by far the most common cause of the symptom. Try tapping the sides of the connectors/wiggling wires to verify/locate the cause.
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Old 08-28-2012, 09:42 AM   #20 (permalink)
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I just want to give an update, which could well be the last. I have now got the other three receivers back from Walkera. They refused to repair one receiver but repaired the other two. I found both of them flew poorly. The heli became rather twitchy and unstable. It was particularly noticeable in FFF. Although I was still able to do flips and inverted flight, there were lots of tail blowouts. It was just downright unpleasant compared to the V120D02S which I flew at the same time. I think I have got to the end of the line as far as repairs are concerned with these receivers.

Last edited by zadaw; 08-28-2012 at 12:18 PM..
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