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Other › issues with BCX 4N1-not easy problem-electrical gurus please respond
10-27-2006 02:57 AM  11 years agoPost 1
John68

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Burgettstown, PA

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Ok, so here's how it started...

The JST connector got stretched and finally the neg lead broke off, so I took the old connector off, and not having a replacement, direct wired the leads to the battery pack. not a problem, except for a split second, when connecting them, I had them reversed, and smoked the MOSFET controller. Not a problem... I went to http://www.digikey.com bought 3 mosfet controllers to replaced it, the other 2 chips I got to repair another fried 4N1 on another BCX, and the other chip as a spare. So, I replaced the MOSFET on the one BCX, and everything works fine.

Now, the one BCX 4N1 that I reversed the leads on...

I replaced the MOSFET that got smoked, and the motors work fine. While I was in there, I put a brand new longer plug for the battery in, soldered to the board. Took the old one out, soldered in a new one from hobbico. Motors work fine, but when I plug in the servos the green LED dims, and if I move the cyclic controls, the LED dims more, nothing happens with the servos, and it slows the motors down.

Why? What else coudl I have fried in there, that would cause this.

I want to add, that when I was in there, I noted that some of the components differed from the first 4N1 that I worked on. some of the components are in different locations, and the antenna is routed differently through the board.

I didn't see any other components that were visably toasty or discolored.
Anyone hazzard a guess as to the problem?

Thanks,
John

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10-27-2006 06:43 PM  11 years agoPost 2
John68

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Burgettstown, PA

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I have the problem whittled down.

If I plug in a receiver battery into one of the servo slots, the other servo will work. This means I fried the component that limits the voltage for the servos, from 7.4 volts to whatever is safe for the servos. looking at the circuit board, the trace from the positive battery wire to the positive servo wire is almost a straight shot. There is only one component in line, in the trace. if I jumper over this component, the servos work but with too much voltage. so... I just have to identify this component and replace it. This is a pain. anyone know what component this is? no markings on it, just a brown box, face mounted...

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10-29-2006 01:09 AM  11 years agoPost 3
stickyfox

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Rochester, NY - US

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It's a Si-Core CX1117-5.0, 5V voltage regulator. I replaced mine with D-K's 497-1243-1-ND. Careful bypassing it though, it also powers the EM78 microcontroller and gyro, which may be less tolerant of overvoltage than the servos are.

-fox

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10-29-2006 01:29 AM  11 years agoPost 4
Gino CP

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Philippines

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You are burdening yourself with DIY. A new one, though expensive, gets you in the air quicker. Spares you back-breaking nights and heartaches. Saves you money from parts and shipping fees that don't get your devices working. PLus you support your LHS.

I've repaired my 4-in-1. Only to to realize its shortcoming. And being in Manila, shipping isn't that cheap. In all, I spent for parts and shipping that amounted to half the cost of a new 4-in-1. And to add insult to injury, it didn't work as I expected. Motors ran but voltage was way low. I'm ordering a new 4-in-1.

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10-29-2006 01:55 AM  11 years agoPost 5
stickyfox

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Rochester, NY - US

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Hey Gino,

Sorry to hear about your repair woes, but it can really pay off if you have the tools and a reliable source of parts. I don't think twice about getting the soldering iron out.

I will say this about shipping fees: digi-key charges extra unless you order more than $25 worth of stuff.

-fox

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10-29-2006 01:06 AM  11 years agoPost 6
Gino CP

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Philippines

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I have the parts, the basic tools, and soldering skills. I do not have the in-depth ability to troubleshoot circuits. And I suspect, many of those who post (and that is why they post) don't either. So for guys like us, it makes more sense to just buy a new unit.

Don't get me wrong. I like the idea of repairing. But when things don't work out, I'd just like to kick me in the head for wasting time and money on something I cannot handle.

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10-29-2006 01:25 AM  11 years agoPost 7
John68

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Burgettstown, PA

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Sticky,

You rock!

That's the part. How ever did you identify it? I have been tooling around with HAM and amateur radio for years, also build my own lighting controllers and do some grunt work for a friend, putting breadboards together. I have never ran across components that look like these. Of course, almost all of the components I am used to dealing with are hole mounted, and not face mounted. Unless it has a wire sticking out o feach end, I'm lost most of the time. I'm forever greatful for the help

John

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10-29-2006 03:04 AM  11 years agoPost 8
stickyfox

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Rochester, NY - US

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I wish I could say I used some high-tech troubleshooting technique but the part was just numbered on one of mine. BTW, the CP has the same part in it (maybe two of them).

I'm into ham radio too, but I don't do as much home brewing lately as I like. I like messing around with robots and musical circuits too. I've tried to get as much into surface mount stuff as I can. The ham magazines are all saying that through-hole stuff will be gone soon, I'm not sure that will happen but the selection seems to be a lot better. The thing I like best is that you don't have to drill holes.

-fox

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10-29-2006 03:17 AM  11 years agoPost 9
Gino CP

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Philippines

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My main and tail motors run. However, it cannot climb and tail loses out when it tries to. What else was toasted in my ESC? I had replaced 2 fets in the main and a diode.

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10-30-2006 01:44 AM  11 years agoPost 10
stickyfox

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Rochester, NY - US

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Are you getting 5V at the servo connectors? If your regulator is weak the FETs may not be turning on all the way. The diode can go too, but you already hit that. I don't think there are any other parts involved with the motor.

-fox

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10-30-2006 03:34 PM  11 years agoPost 11
John68

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Burgettstown, PA

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You might just need to replace the main motor, if you are talking about a blade CP. I didn't get very many flights on a main motor when I had a Blade CP. I stepped up to brushless with an Art-Tech Falcon 3D. No more motor issues for me.

If you already replaced the MOSFET controller, you may want to check your solder connections. solder only conducts about 1/10 the electricity that the copper trace does, even high silver content sodler is weak at best. heat up the pins and really push them into the pads, to make sure you got a good electrical conection. That will screw with things.

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10-30-2006 05:52 PM  11 years agoPost 12
w8qz

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Grand Rapids, MI - USA

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I find it hard to believe the the difference in resistance of solder vs. copper, over the .005" - .020" of length of a solder joint, would be significant, compared to the total circuit resistance. It would be extremely difficult even to measure the change - with 1.499 X 10^-05 ohm-cm (for solder) vs. 1.7 X 10^-06 ohm-cm (for copper).
Now, if the change is a bad solder joint vs. a good one - yes, that certainly will make a difference.

"The helicopter is much easier to design than the aeroplane, but is worthless when done."

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10-30-2006 07:57 PM  11 years agoPost 13
stickyfox

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Rochester, NY - US

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Most people don't realize how poor a conductor solder is. It's not mechanically strong either. I agree with w8qz that using too wide a solder bridge will not dissipate enough power to impair climbout, but I still believe one should always try to make sure the contacts being soldered are as close as possible. In this particular case I'd guess that most of the resistance is in the brushes.

There is enough current flowing in a stalled 4-in-1 to burn through the PCB traces, so I can imagine how a thick solder joint could become the weak link.

Too much flux, or the wrong kind of flux, can also cause problems in FET circuits because it can cause a short that bleeds off the gate voltage. I've personally seen this happen in communication circuitry. If this is the case it will probably get worse when the circuit is heated up and the flux becomes more fluid.

-fox

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10-31-2006 03:37 AM  11 years agoPost 14
John68

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Burgettstown, PA

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w8qz,
I agree that the difference is minimal at best, but then again, I am not looking at the solder joints in question. I have seen a few "professionals in training" put some big old boogers down on a circuit board. I have my tip so well tinned and cleaned all the time that I only use minimal extra solder to a joint, especially doing repair work, where the pads are properly tinned and everything is heated evenly. Most of the time that I do add extra solder is when I use a desoldering iron and blow the existing solder completely off the board, leaving just the tinned pad. Even then, I don't have to add much at all. Usually I can get an even coat on one side of my soldering tip and it is more than enough to complete a nice joint.

I'm not sure how it would effect climbout on the blade cp, as I have never had a bad solder joint on mine(never had to do any work to my cp 3n1) I do know that the tiny brushes in those motors dissapear fast, and that's why I suggested that first. Just throwing some things out there, and the poster can eliminate the possible causes in order. One of the biggest reasons I threw the solder bridging diagnosis out there was because he replaced that component. When I was young, and I would "fix" something, my dad always used to say, "so let me get this straight... you fixed it, and now it doesn't work?" or "so it worked fine, then you touched it, and now it broke?" I will never forget those words as long as I live.

John

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