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Old Dec 06, 2012, 11:16 AM
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Originally Posted by LittleMo View Post
Haha, so I wrote all that for nothing. Well, maybe somebody can benefit.

A diode is a lot more sensitive to heat than a capacitor so it could very well be fried.

Diodes can be pretty generic but there are several different types of diodes. Odds are it's just "regular" (versus Schottky or Zener) with the most important factor being current handing ability.

I can't see the bottom of my board and I don't want to take it apart but most likely it's just a small current normal circuit diode which is pretty generic. That is if it's relatively small and black. If it's on the power circuit for a motor though it could have a higher than normal current rating. Can you see any markings on it? Sometimes the width of the traces on the board can give you an indication of the amount of power flowing through it.
I will take a look tonight, I don't recall any makings. Small black rectangle. Whatever I did, when I turn the power on now , the tail turns on spinning the heli around... The receiver still binds, so there is hope. dummy me.
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Old Dec 06, 2012, 03:06 PM
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I looked at it, and now cleaned up I can see there are markings says 2a :u. It is the diode nearest to the connection post. (My wire colors are reversed). I checked the ohms value in circuit and shows 0 ohm=a short between all three legs. I see there are 2 other identical components with same markings nearby on circuit board. These read open, no continuity. So pretty sure it is fried as I did the best I could with solder braid and cleaned up all excess solders, and double checked the area so pretty sure its shorted internal. I looking for another diode 2a. I looked on one of my dead V911 board and saw a similar component near the tail motor connection, but were not the same. So any tips from here I have nothing to lose but a few dollars if I can narrow down the component.
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Old Dec 06, 2012, 03:26 PM
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Originally Posted by bobfa View Post
I looked at it, and now cleaned up I can see there are markings says 2a :u. It is the diode nearest to the connection post. (My wire colors are reversed). I checked the ohms value in circuit and shows 0 ohm=a short between all three legs. I see there are 2 other identical components with same markings nearby on circuit board. These read open, no continuity. So pretty sure it is fried as I did the best I could with solder braid and cleaned up all excess solders, and double checked the area so pretty sure its shorted internal. I looking for another diode 2a. I looked on one of my dead V911 board and saw a similar component near the tail motor connection, but were not the same. So any tips from here I have nothing to lose but a few dollars if I can narrow down the component.
Are you talking about the part I circled in red? If so that's a FET. A2 would make sense for a FET, or A3 which is what it looks like to me. I'm not sure we're talking about the same part though so mark it if you can. FET's are hard to test while in the circuit. They are also relatively easy to damage with heat or static electricity. I mean all SMT devices are pretty resistant to heat but there is a limit.

If that's the tail motor FET then it's very likely bad unless there is a solder bridge or something we can't see. This might be allowing full constant power to the tail motor which makes sense. Fortunately they're relatively cheap, easy to get, and easy to replace.

What's up with the parts I circled in yellow? They look burned through in the picture but I'm guessing it's just an optical illusion from flux/dirt or whatever stuck on them. Just making sure.
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Old Dec 06, 2012, 04:07 PM
Micro Menace
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Got my Devo tx back and the Genius is in the air once again! Did my first loop with it just now. I think I need some more powerful batteries though. Slow recovery when it flips.
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Old Dec 06, 2012, 04:50 PM
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Got my Devo tx back and the Genius is in the air once again! Did my first loop with it just now. I think I need some more powerful batteries though. Slow recovery when it flips.
Great! Yeah I only practice flipping when the battery is fresh or I'm using the nano-tech's because I'm not too good at inverted flight so need enough power to get back around quickly.

Have you done the servo saver mod?
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Old Dec 06, 2012, 05:00 PM
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Are you talking about the part I circled in red? If so that's a FET. A2 would make sense for a FET, or A3 which is what it looks like to me. I'm not sure we're talking about the same part though so mark it if you can. FET's are hard to test while in the circuit. They are also relatively easy to damage with heat or static electricity. I mean all SMT devices are pretty resistant to heat but there is a limit.

If that's the tail motor FET then it's very likely bad unless there is a solder bridge or something we can't see. This might be allowing full constant power to the tail motor which makes sense. Fortunately they're relatively cheap, easy to get, and easy to replace.

What's up with the parts I circled in yellow? They look burned through in the picture but I'm guessing it's just an optical illusion from flux/dirt or whatever stuck on them. Just making sure.
Yes, the one you have circled, nearest to the terminals. The other two are same, but they do not have continuity between pin legs.

The other parts are just different color, partly due to camera lighting..

So these FETs , searching google, came up with this component calling it a transistor== http://i.pchub.com/i/Semtech-Transis...06-b-83414.jpg

They are just 27 cents each...Would that work?
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Old Dec 06, 2012, 05:22 PM
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Yes, the one you have circled, nearest to the terminals. The other two are same, but they do not have continuity between pin legs.

The other parts are just different color, partly due to camera lighting..

So these FETs , searching google, came up with this component calling it a transistor== http://i.pchub.com/i/Semtech-Transis...06-b-83414.jpg

They are just 27 cents each...Would that work?
Yeah, finding the correct part can be tricky. I wonder if anyone has already done it. They are MOSFET's which is a type of transistor. The tricky part is determining what current rating it has and whether it is P channel (P-FET) or N channel (N-FET). As for the part number I don't know if this one is 2A, 2A3, A3, or what so that makes searching difficult.

This one I have seen mentioned for replacement on the V911. It's a 20 volt, 2.5 amps, N-FET:
http://www.digikey.com/product-detai...6-1-ND/2531243

I don't know if that would work or not, the FET's on the V911 are marked A2sSB or maybe A2sS8 I can't tell but it's a different marking than the one in your picture. If the one on the GCP is really an "A3" and A3 means "more current" than A2 then it may have a higher amp rating.

This might require some research. I'm willing to bet someone, somewhere already knows what part to use because these things burn out occasionally anyway.

Edit:
It seems the Mini CP uses a 7.5A N-FET array so I'm guessing the V911 FET is not going to work. But like I said, the FET's blow occasionally like when the tail motor wires short out so the correct part to use is surely posted out there somewhere.
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Old Dec 06, 2012, 09:27 PM
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A little internet digging finds thsi pciture on Benlee's Genius site.

The little component labeled 2A is a transistor on right mmbt3906w They are 27 cents each and 3 dollars shipping.
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Old Dec 06, 2012, 11:17 PM
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A little internet digging finds thsi pciture on Benlee's Genius site.

The little component labeled 2A is a transistor on right mmbt3906w They are 27 cents each and 3 dollars shipping.
Nice find, it's not even a MOSFET, just a regular 3906 transistor, one of the most common.

I wonder what that has to do with the tail. Anyway, if it fixes it then great!
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Old Dec 07, 2012, 08:34 AM
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No clue, but they are part of the tail motor power supply for sure. Glad we figured out what they were, you were right, allot of these look the same but are not.. Almost was going to order MCPX mosfets. The next step will be learning to solder SMT. I am fairly proficient at soldering, but this SMT will be a challenge. I will post later on the results. Its all good to be able to try and fix these boards.
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Old Dec 07, 2012, 10:25 AM
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Got my Devo tx back and the Genius is in the air once again! Did my first loop with it just now. I think I need some more powerful batteries though. Slow recovery when it flips.
Been flying mine for a couple of months now and here are some things I have learned. Watched finless Bobs reviews on this heli over on HF, and he was spot on as concerns flips , loops etc. The brushed motor will bog, so just go easy on the collective when going inverted and allow the headspeed to catch up. Mine flies great inverted. As concerns the motor and how long it will last, I set my timer for 4 minutes. It might fly longer than that, but that little motor will fry itself. Also, give it a few minutes to cool down between flights. I have many, many flights (and some crashes) on my original motor and it's still going strong. Good luck. Jim
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Old Dec 07, 2012, 11:44 AM
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With regards to inverted flight, I also noticed I don't get as much lift when I 'm inverted as I would like. What 's the best way to increase neg pitch? Can that be adjusted with the tx? Could I just move to the outer hole of the servo horns and add in some dual rates to tame it down a little?

Or maybe I should just fly it for a while and not mess with it at all.
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Old Dec 07, 2012, 11:45 AM
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What does your pitch curve look like?
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Old Dec 07, 2012, 12:12 PM
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IDK.... It's whatever the factory sets it at. I just got it back yesterday I haven't really gotten into it though. One more question while I'm at it. When programming in D/R, why does the menu show Pos- 0,1,2 when the D/R switch only has Pos - 0 and 1?
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Old Dec 07, 2012, 12:29 PM
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IDK.... It's whatever the factory sets it at. I just got it back yesterday I haven't really gotten into it though. One more question while I'm at it. When programming in D/R, why does the menu show Pos- 0,1,2 when the D/R switch only has Pos - 0 and 1?
I don't have a devo but I think I remember reading that the third one is not used because the switch is just a two-way switch.

You might want to look at your pitch curves and make sure it's at least symmetrical when in stunt mode. I use a straight line from -50% to 50% on my 9x.
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