Originally Posted by 1Pilgrim

Hate to bring everyone down on a holiday weekend, but my 120's been grounded since last Tuesday with what sounds like a bad esc.

I wanted to take my batts down for storage last week before heading out of town. After doing the first few the boring way (charger) I decided to try flying a few of them for 3 minutes each. My scatter diagrams showed that at three minutes the voltage would be down to around 3.85V. It should have worked, but...

The first flight was fine but a minute or so into the second flight the heli went to full throttle and pinned itself to the basement ceiling! I tried everything I could think of, even turning off the tx, but to no avail - the li'l dickens just kept bouncing off the ceiling like an oversized crane fly. I reached up and grabbed it and had my wife hold it by the skids while I disconnected the battery. She was not amused.

After flushing the adrenaline out of my system I turned on the tx and loaded up a fresh batt. The heli responded normally to swash and tail rotor inputs but the main motor only answered the call intermittently, maybe 30% of the time. I could hear a high-pitched whine whenever the throttle was advanced, even when the main motor wasn't responding.

Is there a fix for this or do I need a new board or could it be something else entirely?

I think it sounds like a circuit fail on the board, myself. I can't picture in my mind, anything else it could be.

Originally Posted by stuball56

That would be horrible if it happened outside! You would lose it. I fly mine outside whenever the weather is ok, (no wind).

Yeah, it's too cold and windy here so we're back indoors for the winter. I had 12 good flights at the gym the previous Saturday. It would've been quite a show if the heli had gone to full throttle and started banging its head on that high ceiling!

I'm gonna look for burn marks on the board and maybe apply some alcohol with a Q-tip. If I can't resurrect the board I may decide to spring for a whole new heli - this one has well over 500 flights on it in the past 18 months.

I took off the canopy, head and pushrods then disconnected the main and tail motors and removed the brick leaving the shaft, main gear and motor installed on the heli.

Plugging the battery directly into the main motor did spin the motor and shaft - so far so good.

Turning on the tx and plugging the battery into the brick did bind the brick to the tx and allow the swash servos to function - so far so better.

Plugging the main motor into the brick did allow the main motor to respond to throttle inputs - more joy, but it only lasted until the next step.

Aye, but here's the rub. Plugging the tail motor into the brick allowed the tail rotor to respond to stick inputs (throttle and rudder) but the main motor no longer responded to the throttle through the brick; now it only runs when plugged directly into the battery.

There are no traces of burn marks on the board and I never detected any electrical smells; even so it looks as though something is definitely wrong with the board. My lhs quotes $65 US for a new one; anybody have a cheaper source?

Originally Posted by 1Pilgrim

I took off the canopy, head and pushrods then disconnected the main and tail motors and removed the brick leaving the shaft, main gear and motor installed on the heli.

Plugging the battery directly into the main motor did spin the motor and shaft - so far so good.

Turning on the tx and plugging the battery into the brick did bind the brick to the tx and allow the swash servos to function - so far so better.

Plugging the main motor into the brick did allow the main motor to respond to throttle inputs - more joy, but it only lasted until the next step.

Aye, but here's the rub. Plugging the tail motor into the brick allowed the tail rotor to respond to stick inputs (throttle and rudder) but the main motor no longer responded to the throttle through the brick; now it only runs when plugged directly into the battery.

There are no traces of burn marks on the board and I never detected any electrical smells; even so it looks as though something is definitely wrong with the board. My lhs quotes $65 US for a new one; anybody have a cheaper source?

Spend the extra $$ and get a BNF and use your old one for spare parts.

Originally Posted by Jake8131

Spend the extra $$ and get a BNF and use your old one for spare parts.

Definitely leaning that way, especially with the indoor season just starting. I learned so much from my first heli that it'd be fun to mod and upgrade a brand new one. Anybody know if the new ones are still identical to the original?

My son finally destroyed his tail motor after about 3 months of flying. But I decided to ditch replacing it and have him work on my old walkera v120D01 as preparation for a CP heli-- the V120D01 is fixed pitch, but does not have that much self stabilization and is a great trainer for a CP. Unfortunately, that heli has been discontinued by Walkera, but I have enough spares to keep him airborn for awhile.

I wish Blade would enable a good intermediate/transitional FP heli in the 120 size (like the MSRx...)

Chief

Originally Posted by 1Pilgrim

I took off the canopy, head and pushrods then disconnected the main and tail motors and removed the brick leaving the shaft, main gear and motor installed on the heli.

Plugging the battery directly into the main motor did spin the motor and shaft - so far so good.

Turning on the tx and plugging the battery into the brick did bind the brick to the tx and allow the swash servos to function - so far so better.

Plugging the main motor into the brick did allow the main motor to respond to throttle inputs - more joy, but it only lasted until the next step.

Aye, but here's the rub. Plugging the tail motor into the brick allowed the tail rotor to respond to stick inputs (throttle and rudder) but the main motor no longer responded to the throttle through the brick; now it only runs when plugged directly into the battery.

There are no traces of burn marks on the board and I never detected any electrical smells; even so it looks as though something is definitely wrong with the board. My lhs quotes $65 US for a new one; anybody have a cheaper source?

Do you mean that the main motor was functioning properly before you plugged in the tail motor? I've had this happen and replacing the tail motor solved my problem. Sometimes, when the tail motor gets fried, it takes away amps from the main motor. Try another tail motor before buying a whole new one.

Do you mean that the main motor was functioning properly before you plugged in the tail motor? I've had this happen and replacing the tail motor solved my problem.

Had the same problem on my MSR and a tail motor fixed it.
Gary

I just bought a 120SR RTF after months of reviewing helis. I was really excited, until it lifted off for the first time. It acted like it was a pendulum moving several feet back and forth, went in circles (toilet bowl effect), and didn't follow the input from the remote very well. I have only had it in the air a few times and then it was pretty much just to trim it. It acts like the 120 in this you tube video:
http://www.youtube.com/watch?feature...v=bW4At9fPCq4#!
I tried rebinding it to the transmitter, tightening and loosening the screws in the blade grips, but nothing seems to help. Any suggestions what to look at next? I ordered a Rackon CNC flybar in hopes that will help. Thanks for any help.

That doesn't look too bad to me. Pop off each link one at a time and polish the balls with a piece of paper bag. Lube the balls with a plastic safe lube (i use Break Free CLP). Insure the flybar is straight,,..do this by eye. Carefully bend to shape. Your heli is demonstrating a flybar problem.

Mike.

Originally Posted by hereathome

I just bought a 120SR RTF after months of reviewing helis. I was really excited, until it lifted off for the first time. It acted like it was a pendulum moving several feet back and forth, went in circles (toilet bowl effect), and didn't follow the input from the remote very well. I have only had it in the air a few times and then it was pretty much just to trim it. It acts like the 120 in this you tube video:
http://www.youtube.com/watch?feature...v=bW4At9fPCq4#!
I tried rebinding it to the transmitter, tightening and loosening the screws in the blade grips, but nothing seems to help. Any suggestions what to look at next? I ordered a Rackon CNC flybar in hopes that will help. Thanks for any help.

Looks to me like a cracked main shaft causing the shaking.

Originally Posted by 1Pilgrim

Hate to bring everyone down on a holiday weekend, but my 120's been grounded since last Tuesday with what sounds like a bad esc.

I wanted to take my batts down for storage last week before heading out of town. After doing the first few the boring way (charger) I decided to try flying a few of them for 3 minutes each. My scatter diagrams showed that at three minutes the voltage would be down to around 3.85V. It should have worked, but...

The first flight was fine but a minute or so into the second flight the heli went to full throttle and pinned itself to the basement ceiling! I tried everything I could think of, even turning off the tx, but to no avail - the li'l dickens just kept bouncing off the ceiling like an oversized crane fly. I reached up and grabbed it and had my wife hold it by the skids while I disconnected the battery. She was not amused.

After flushing the adrenaline out of my system I turned on the tx and loaded up a fresh batt. The heli responded normally to swash and tail rotor inputs but the main motor only answered the call intermittently, maybe 30% of the time. I could hear a high-pitched whine whenever the throttle was advanced, even when the main motor wasn't responding.

Is there a fix for this or do I need a new board or could it be something else entirely?

Sounds like a fried FET. I've discussed it here more than a few times and relatively recently. I bought mine in that condition on the cheap last winter. It's more common with the 120 than we'd like it to be.

Bought my new board from valuerc on ebay for a little over $40 at the time. Guys buy 120's and part them out.

Originally Posted by stuball56

That would be horrible if it happened outside! You would lose it. I fly mine outside whenever the weather is ok, (no wind).

It's happened to more than a few people I know of with this specific bird.

Originally Posted by Wind Spirit

Hi, I have not heard of this problem before, :

Yes, you have

I would not use a Rakon flybar, yet. The SR120 works best with stock parts. When you start modifying, you begin to incur 2nd and 3rd order of problems that you will not understand. I know--that's how I started out in this hobby!

Check what Mike says about smooth functioning links, and that your flybar and main blades are tracking perfectly. If you do not know how to do that, let us know, we can help. Check that the tail boom is not cracked or loose. If everything is in order, your gyro may be off and you should contact Horizon Hobby. They back their products.

Addendum: The video looks fairly normal, so that is not bad. The 120 is made to keep flying--hovering is more of an art.