What happened to the receiver?

[steelo]

Hi guys,

We seem to be having issues with the electronics in my wife’s Tomahawk. Over the weekend, she ran it with a 2s lipo battery and after about 15 minutes of running, she said “My car’s smoking”. I noticed that the motor was scorching hot and smelled like something was burning, so I immediately turned everything off and disconnected the battery. After letting it cool for about an hour, we ran it again…the car seemed a bit slow but I figured the battery was probably weak by then. Well, yesterday after work, it was nice outside so she wanted to run it again. When everything was plugged up and turned on, the car would stutter really bad. Eventually, the motor stopped working altogether. I figured, well shucks….her motor probably is shot. Now, the receiver won’t turn on. When you turn the switch on, the steering twitches, but after that nothing will move. The radio is a 2 month old Tactic 2 channel radio and we are using a Hobbyking 90 amp‘X-Car’ ESC with a Turnigy 2s lipo battery. The ESC turns on and everything with the ‘bad’ receiver, but doesn’t go through it’s full ‘song’ when you turn it on.

I tried another receiver I had lying around and the steering now seems to work fine…of course, the motor barely turns. Now, I know the motor is shot (no biggie because it was just a spare J-motor), but what the heck happened to her brand new radio? Could the motor burning up have cause some kind of short which ruined her receiver?

Thanks!

[Backlash]

Could the receiver have gotten wet, or dirt inside it??

Did the ESC get hot as well? (Maybe the heat from the ESC affected the receiver?)

Do you have any way to measure the BEC voltage in the ESC? (Maybe it is too high for the receiver and damaged it?)

Maybe you just got a dud receiver.. (Warranty?)

[steelo]

Hi,

I forgot to mention that I did check the ESC and it was barely warm. It was bone dry outside that day and last night I pulled the receiver apart and it looks to be pretty clean inside. Unfortunately, I cannot locate the receipt for the radio and the hobby shop where I purchased it is less than welcoming with any kind of returns.

[lentner3]

Firstly get that motor changed in case it is shorting out as that could damage the esc. Then check the voltage from the esc to the receiver, should be 5-6 volts if it has a Bec built in which I'm fairly sure those 90amp ones do but not 100% sure. The receiver may have been fried by the esc if it does not have a built in Bec.

[lentner3]

Failing that try using a few aa batteries to power the receiver and one servo to check the radio gear. As the steering servo is twitching it could be the transmitter so check the tx is working ok. You could also try to re bind the tx and rx. When you tried another receiver was it with another transmitter also?

[steelo]

Hi Lentner...yes, I tested it with a completely different radio system that I have been using in other vehicles and it seemed to work 100% fine with it. As far as the twitching, the servo momentarily ‘twitches’ only when I turn the power switch on. With radio function, the servo and ESC do nothing when given input from the transmitter. The receiver also has a red LED light which no longer illuminates when you give it power.

I thought MAYBE I would be able to bind my transmitter to my good receiver since they are both 2.4ghz DSM (or whatever it’s called) but so far, no luck…

[lentner3]

no light on the rx does point to a failed receiver, but can't work out why that would happen when the motor fried as they are almost two separate circuits unless it was just a coincidence. Also begs the question, why did the motor fry in the first place? what motor are you using and was the car run in thick grass or similar terrain that might slow it down and increase resistance to the motor?

[steelo]

Yeah, she was running it on loose, flat dirt. We were using a 2s lipo battery with a silver can 27T motor at the time and the area is so big that I’d say she was at full throttle 90% of the time. It was probably around 55 degrees outside so I’m pretty sure the temperature didn’t cause it to overheat.

I forget what the gear ratio is set at…I know the Tomahawk manual gives you two options and I’m pretty sure it’s geared for a higher top speed.

I went ahead and ordered an Axial 27T motor for it, my wife is new to RC and wanted to get that motor because it’s what towerhobbies recommends…LOL

[lentner3]

could well be two separate issues then

[lentner3]

have you tried disconnecting the esc and using a battery pack to power the rx seperatley with one servo? just to make sure it isn't the esc.

[steelo]

No, I haven’t tried that yet but it sounds like a good idea. Maybe there is a chance that the output to the receiver is bad.

I just looked up the ESC on hobbyking and it's a 45A, not a 90A. The description also says the BEC output is 5.6v/2A switch mode built in...According to the manual for the receiver, it is supposed to handle up to 7v so the ESC shouldn't be the culprit for the receiver frying...

but I'll try the separate battery idea tonight =) Thanks for all of your help!

[lentner3]

all your assumptions are right, the esc has bec so shouldn't be the culprit but some rx are more sensitive than others. It makes sense to check but as you said doesn't make add up. If the rx is fried thats fine but you really need to make sure it doesn't happen again if something in your setup has caused it.

[steelo]

Very true, I’m going to have to measure the voltage the ESC is putting out to the rx to make sure the claim of 5.6v holds true. I’m hoping that the receiver lights up when I plug it into a 4 AA battery pack. That would mean the ESC output is bad…If true, I could just plug one of my simple but trusty Tamiya ESC's up instead of spending $40-50 on a new receiver.

[lentner3]

Very true, I’m going to have to measure the voltage the ESC is putting out to the rx to make sure the claim of 5.6v holds true. I’m hoping that the receiver lights up when I plug it into a 4 AA battery pack. That would mean the ESC output is bad…If true, I could just plug one of my simple but trusty Tamiya ESC's up instead of spending $40-50 on a new receiver.

Why would you spend that much on a rx?

there are some great cheap 2.4 ghz sets on hobbywing that are much cheaper and higher spec than your radio.

[steelo]

Very true, that may be a bit of an exagerrated price. I found one on ebay for $20, I'm pretty confident the transmitter is still okay

[lentner3]

Even at £20 I would not bother. Most of the sets on hobbyking are superior and the replacement rx cost only £2-3. That way you can have lots of spares or run many cars with the same tx.

[steelo]

Okay, thanks for your help!

[steelo]

Holy cow…I checked out the radio’s on hobbyking and now regret buying the replacement rx for her Tactic radio. I could have bought an entire radio system with 5 times the features for the same price as just the receiver

[lentner3]

no gonna say ITYS

[steelo]

haha!