Spektrum SLT3 - Odd Behaviour, Steering Works But No Throttle

[TrueBlue 45]

OK, so I purchased this transmitter and receiver from an eBay seller who had removed it from his recently purchased Big Rock. It was sold as "For Parts or Not Working" so no refund, but at the same time the seller was unsure whether he was doing anything wrong when it came to binding the transmitter and receiver. As it turns out, he may very well have been doing it correctly, as something does seem faulty somewhere.

I have it binded to the SLR300 receiver no problems. Steering works no problem, as do the steering adjustments. Throttle however... is a literal no-go. There is no response from the throttle at all. When I turn on the ESC (HobbyWing QuicRun 1080) it blinks, usually indicating no transmitter signal, but steering does work. It appears that the transmitter is not sending any signal from the throttle, so the ESC doesn't initiate fully, except the steering.

I've tried calibrating the ESC, but since it's not receiving a "go" signal, calibration doesn't work. I've taken the transmitter apart (since I can't return it or get it replaced under warranty) and I can't see anything obvious. No components are damaged, burnt, missing (I think), the circuit board is undamaged, pretty much nothing out of the ordinary.

I know the trigger potentiometer works as I was able to test it on the steering, so the issue lies from the connector on the board to... where ever it goes after that.

Also, the ESC works fine with other receivers, and the SLR300 won't work with other speed controllers in other cars. I CAN get the throttle to work if I use the AUX buttons for forward and backward, but that's not really useful. So the ESC is definitely working with the receiver to some capacity, but the throttle channel is just... dead.

It COULD be the receiver I suppose, but I don't have any means of testing, without buying another receiver or transmitter.

So I've run out of ideas, after trying for a good 3-4 hours fault finding... I found no obvious faults. Google isn't very helpful as it just loves to omit the word "SLT3" a lot.

Does anyone have any clues? Any ideas? Any thoughts? Even a spare receiver you wish to get rid of. Any help is a good thing. Please and thank you!

 

[alvinlwh 5895]

Plug the ESC into CH 1 and see if it works normally with steering. If yes, then CH 2 on something is fried. You got a second Rx that you can test? 

EDIT: Just saw on your Rx they are marked as STR not CH 1.

[TrueBlue 45]

Well, throttle DOES work with the wheel when plugged into STR. With the steering plugged in THR, that also works.. it is very jittery, but it does steer with the trigger. No second Rx in order to test though.

However, an interesting discovery. I've tried the receiver in 6 different Tamiya's, with varying ESCs, including Tamiya, HobbyWing (brushed and brushless) and an old unknown branded one. It fails to work in FIVE of them. It works in my Konghead, which currently has a Traxxas XL-5 ESC installed. For some reason, calibration worked and can control the throttle with the trigger as I'm supposed to. If calibration worked with the ESC's, it might start working properly. But without a "go" signal, there's no calibration, therefore no throttle.

EDIT: Also decided to test this in my Traxxas Rustler 4x4 VXL. Interesting... it works perfectly. So both the Rustler and Konghead have one thing in common: they both use Traxxas receivers. A VXL-3 and an XL-5. So why is the Spektrum only working on Traxxas ESC's? Very peculiar.

[alvinlwh 5895]

10 hours ago, TrueBlue said:

With the steering plugged in THR, that also works.. it is very jittery

So why is the Spektrum only working on Traxxas ESC's? Very peculiar.

This sounds like your CH 2 is having a problem somewhere, sending bad signals to the servo, and since you do not have a second Rx, it will be difficult to find out if it is the TX side or RX side that is fried. 

It works with some ESC probably (my guess) because those ESC are better able to "resist" bad signals or something like that. 

[TrueBlue 45]

Even though the steering is jittery in the THR Ch2 channel, the forward/reverse movement is not (when in THR Ch2). It's super smooth with no juddering. I should try to get a second receiver so I can test. If the same thing happens, maybe it's a faulty transmitter instead.

EDIT 2: I have uploaded a YouTube better explaining the problem, as well as some footage of how the transmitter and receiver behave when used:

https://youtu.be/uJOprpxVW5s