I just burned up my second Heli-Max LPM E-board Axe CPv3. I need help figuring out what is wrong here before spending any more time and money.

The first Heli-Max LPM E-board Axe CPv3 likely burned up after I had replaced the tail motor (loose connection) with a new motor. I replaced the motor again (3rd), then realizied the first Heli-Max LPM E-board Axe CPv3 was badly burned up, not the motor, when the 3rd motor did not work. Then, I replaced the Heli-Max LPM E-board Axe CPv3, and again did not find any tail motor operation, as this Heli-Max LPM E-board Axe CPv3 also starting burning up in the same spot.

I welcome all suggestions here on firstly figuring out what is wrong, and secondly how to correct it from reoccurring.

For a component to burn it must be getting hot.

In the electronics realm that usually equates to excessive current flow (through it).

This usually is the result of a shorted or reduced resistance path to ground.

So aside from a manufacturing or component defect, (out of your control) it's likely a short somewhere.

It maybe too late for the latest e-board too as the [heat] damage you say is already visible.

If you have a DMM you can measure the resistance of the leads to the motor and look for a short.

I don't know what the motor's resistance shoud read off hand but it will not be zero. You can test the motor with a battery pack to see if the motor is good.
About 3-6 volts should be safe for a quick test. If it turns then it is likely not a bad motor.

The tail wire can chaffe and be shroted by the boom or excessive heating of the motor connections during soldering/replacement can damage them possibly resulting in a short internally or to the case. Check that the capacitor has not somehow shorted or it's leads have.

The root cause may be difficult to find now if all your parts are damaged. You need to KNOW something is working OK to further the "divide & conquer" style de-bug process.

There is a screw that holds the tail motor mount to the tail boom which has caused problems in the past. The wire for the tail motor runs through the plastic tail mount and some have found that the screw has penetrated the wires inside. Have you pulled the wire from inside the tail boom to be sure its not been shorted?

Sorry about your problems.

Given that the screw that holds the tail motor mount to the tail boom has caused problems in the past, I visually checked the wire for the tail motor runs through the plastic tail mount . I removed the screws at the tail motor mount and removed it from the shaft, but did not observe any damage to the wires inside. I have a DMM and will measure the resistance of the leads to the motor to look for a short.

I tested the 3rd (as well as 1st with loose connection and 2nd) motor with a 6V battery pack to see that it operates as expected with power. Thus, it was not a bad 3rd motor.

Perhaps, heating of the motor connections during soldering/replacement damaged the E-board resulted in a short internally or to the case. In hindsight, I should have removed the connection from the E-board to the motor before soldering the new tail motors to the wiring. However, I thought that the motors were burning up, not the E-board until yesterday.

How do I check that the capacitor (on the motor, right?) has not somehow shorted or it's leads have?

As r_william said, use a multimeter to check the resistances across the wires, the motor, etc. (set it to milliohms if it doesn't auto-scale).

It is unlikely that unsoldering/soldering the tail motor damaged the ESC on the 3 in 1.

There are only two ways I think that could happen- Heat, but the wires would have melted the insulation and it would take awhile for the heat to travel all the way to the ESC. You would have noticed it (smelled it too). The other would be ESD- if the soldering iron is not isolated from the AC mains it is possible to "zap" anything in the current's path.

As far as the capacitor, if you tested the motor with a battery and the cap is attached, that's not it either. You can test it by measurng the resistance across it. This is not a likely cause but something to be aware of. These small caps don't usually short but rather "pop" when abused and that would be visible.

Yes, I tested the motor with a battery and the cap is attached, so the capacitor should be fine. I will get the DMM out tomorrow to eliminate the wiring from the E-board to the tail moror as being the problem.

I just posted a Wanted Ad at RCU on purchasing an abondoned, discarded or crashed Heli-max AXE CP V3 (version 3 only) to obtain a working Heli-Max LPM E-board Axe CPv3, along with the other parts for spares.

Please click on the web link below to see this Wanted Ad.

[link=http://www.rcuniverse.com/market/item.cfm?itemId=477879]RCU Electric Heli Wanted Ad[/link]

The e-board/3 in 1 from an Axe CP-l (V2?) will work too, the only difference is the V3 version has the/an LPM module attached.

I shorted my 3 in 1 board when I used too long of screw for the tail motor. I was able to repair the board by replacing the 8 pin dual n channel mosfet that is on the opposite side with the gyro.

Then after replacing that I found the small surface mount npn transistor next to the fet was shorted. I didn't have that so I used a to-20 case npn transistor pulled off of the board by old servo wires.

Type in the part # of the mosfet on digikey.com or I can send you another (I bought five).
Hope this helps.

Toydocter, thank you for the suggestion, but my circuit board skill are very limited, maybe solder a capacitor or resistor, so I am doubtful about making the changes that you suggested.

No doubt, he has tools too... SMT is not for the novice.

Still looking for the E-board (3 in 1 controller), but will consider all crashed Helimax AXE CP's.

Heli-max is providing me a replacement, which I will install with a 3amp fuse on its wiring to the tail motor (only 2amp supplied there.)

did you need to show a reciet for the motor to get a replacement?

Was this reccommended by H-max customer service?

Generally speaking it is not wise to "up" the vaule of a fuse or (or circuit breaker). It is there to protect the wiring and other components and its failure is telling you something is not "right".

If you must alter the design it is acceptable to replace the fuse with a "slo-blow" type of the same rating, but that does not guarantee a more "sensitive" part won't fail first.

I never had a fuse issue with my Axe (and did not know one was even there). It is not mentioned anywhere and this is the first I have heard of its existence.

If there is one [fuse] there why did it "blow", burn, or otherwise cause a failure of the 3 in 1?

A fuse was not recommended by H-max customer service. I am not aware of any fuse installed on the AXE CP and did not intend to imply that it had one. The installation of a fuse was suggested by someone other than Heli-max service.

I agree that the E-board "failure is telling you something is not "right"."

OK, after re-reading your post..."(only 2amp supplied there.)" you obviously meant only two amp draw is EXPECTED at the tail. My assumption, my bad.

But then the question is.. is that 2 amps max, or avg.? Big difference. I've never had to measure or test it.

Well I hope your right about the required value because if the fuse blows in flight you won't be worrying about the fuse for a while.

Is there something binding the motor? With a V3 there is no gear, it's direct drive unless you've converted it or something.

Is the tail rotor rubbing against the motor housing or mount somehow causing increased friction or drag? This would cause current draw problems.

My advice is based on the fact that there are three components involved here, the tail ESC portion of the 3 in 1, the wires to the motor, and the motor.
Have I missed something?

If you've replaced or verified all three, I'm at a loss here.

Search this RCGroups forum using the word "fuse" to answer your questions above.

http://www.rcgroups.com/forums/showthread.php?t=610525

I found an article on "Upgrading your Mini Electric Helicopter for protections for your motor electronics, main rotor drive gear and drive motors" at one of the RC forums (likely RCU) after posting that I was burning up two Heli-max AXE CPv3 E-boards (4 in 1 controller). I have visually checked the wiring to the main motor and tested it to measure zero resistance with a digital multi-meter, as desired.

As suggested in this article, I installed a 3 amp mini-fuse on the wiring to the tail motor, which I suspected to be the cause of the problem after replacing two of these tail motors. After test starting the AXE CPv3 both without and with the main motor connected, I shorted out this 3 amp mini-fuse and its replacement.

Should I next move up to a 5 amp mini-fuse?

I welcome all suggestions here.

This sounds really strange to me. If your smoking a fuse instantly on startup, there must be a short somewhere in the tail motor circuit. I have an Axe CP that I've upgraded to the V3 version, and I also had to desolder the tail motor to install the carbon fiber boom. After finishing the upgrades, the bird works perfectly, no tail motor fuse. I'm attaching a photo of my tail motor showing the wiring & setup. Does yours look like mine?

You mentioned extra heat during your soldering. Did you replace the capacitor on the tail motor as a test? Capacitors 'soak' up current to provide a softer start to the motors. Maybe yours is damaged from heat. Components are made to take some heat for a short period of time, but not a very high temp for a long time. You may have also melted something internally in the plastic motor brush holders. Did you try a different motor? If you did, did you also solder the different motor? Are you just touching the connections with your soldering iron just long enough to melt the solder and make the connection? What type of soldering iron are you using? Also, you can see in my photo how the wires touch the heat sink. Perhaps you have some damaged wire insulation that is grounding out during the startup / vibration of the heli?

Hopefully I've given you some things to look at / think about. Good luck!

DrS

Does yours look like mine? Yes

Did you replace the capacitor on the tail motor as a test? No, as Heli-max said this is only a filter for noise, not impacting the amperage.

Did you try a different motor? No, two EFLH1322 are on order to try.

If you did, did you also solder the different motor? This is my 3rd motor that I have soldered - it works, but blows the 3amp fuse.

Are you just touching the connections with your soldering iron just long enough to melt the solder and make the connection? Yes

What type of soldering iron are you using? Resin core type from Radio Shack for hobbiest.

Perhaps you have some damaged wire insulation that is grounding out during the startup / vibration of the heli? While I did not remove the entire, it looked fine when I removed the motor for its replacement. I will replace the wiring that has zero ohm resistance using DMM, if nothing else is found.

I am waiting for a call back from Heli-max helihotline on moving up to a 5amp fuse.

Mr bdelmonte,

This whole fuse thing is puzzling to me as I never saw the need with my Axe CP-l (v2?).

As an electronics tech with 23 yrs. experience I clearly understand the purpose and function of fuses so that's not what I mean by puzzling.

It is likely that 3 amp is not enough but I have never even thought of measuring mine as I had no problems.


When Hmax published the procedure for adding the HH gyro they suggest the ElectriFly 12 amp brushed ESC. If they are following typical design margins that would be 50% greater than necessary. So using that "rule of thumb", one could infer that it draws 6 amps or maybe a bit more. This would also depend on the drag or load put on the motor in flight which is dynamic depending on the maneuver.
Maybe you or someone out there with a stock Axe v2 or v3 could measure both the max delivered voltage and max current draw of the tail motor and eliminate ALL the speculation about it.

I have read (in forums) people using the 7 amp ESC instead but I never read anywhere if that was reliable or not. If it does draw close to 6 amps that would be a bad idea and with a price difference of only $5 it doesn't seem worth it.

Of course none of this current capacity of the ESC issue effects the life of the motor. For a brushed motor its life is primarily determined by brush wear rate. Over voltage would also cause failure or damage thus lifetime issues but that is not the case here.

To restate and confirm what others have written, heat stress from soldering can damage the motor too and since the end cap is plastic it may cause some mechanical deformation leading to premature failure INCLUDING shorting as well.

I believe I mentiond before that the capacitor would have to be internally shorted or it's leads creating a short somehow (too much solder for example) for it to be a problem. As Hmax has said it is there to supress EMI (static) created by the arcing of the brushes inside the motor.

There is no need for this fuse and it maybe distracting you from the real cause(s).

Can you post a photo or get a friend to help you post some? We all want to see you flying instead of fixing and could be more helpful if we could see your equipment.


edit for spelling

I don't think you want the resistance to be zero. I just checked my motors and found the N60 motor to have a resistance of 20 ohms and the GWS motor to have 4 ohms. The GWS motor is mounted and has the full length of wire soldered to it. Either way, its not zero.

I flew my Heli-max AXE CPv3 today with the two fuses installed - namely 5amp for tail motor and 10amp in holder for main motor. I have included the a pic of this tail motor.

The first flight of approximately 10 min went fine, but the second flight ended in a crash due my loss of control with nose in hover. No fuses blew during these flights, but I need to recheck after the crash. The parts for repair are on order for those not already in my stock on hand.

My pic would not upload due to its size, but all it showed was hot glue on the connections to the tail motor.

I flew my Heli-max AXE CPv3 three times this week with no problems. I suspect that the loose bushing connection in the tail motors after a crash or roll-over was shorting and causing my prior problems with burned up E-board.

Cheers!