HS-7955TG with MMP woes

[10x8]

G'day all,

Need a bit of help here. I’m trying to get a HiTec HS-7955TG servo to work with my MMP. I’m using a new Spek DX3C tx/SR300 rx, CC 10amp bec, Xerun 21.5T motor & Turnigy 4000NiMh 2s 40c lipo. This is in my SCX10 Honcho truck. Stock 20/87 gear.
What happens is, the RX green Spek light, flashes intermittently, wheels pulse, servo jitters, stops, goes etc.

I’ve tried the bec at 5,5.5 & 6 volts. Tried all setups with Castle link. Servo is fine as I’ve tried it with the Axial AR-3 RX & esc. Works fine?? Everything worked fine before I tried this servo with the MMP. Please can anyone tell me what I’m doing wrong? Axial servo works with MMP, my wire solders are A1, rx connections are solid, sensor cable fine, binded fine. I’m stumped.

Regards
Pete

[Charlie-III]

1-Is the external BEC direct to the servo, or through the RX?
2-What happens if you just unplug the servo from the rig, does the RX work?
3-Does another servo work in that rig?
4-If you wired the BEC direct to the servo, is the servo black (or brown) wire going to the RX (Spektrums are know for being picky on this....they WANT the ground).


This should NOT be a CC ESC issue.....period.

[10x8]

Originally Posted by Charlie-III

1-Is the external BEC direct to the servo, or through the RX? RX
2-What happens if you just unplug the servo from the rig, does the RX work? Yes
3-Does another servo work in that rig? Yes
4-If you wired the BEC direct to the servo, is the servo black (or brown) wire going to the RX (Spektrums are know for being picky on this....they WANT the ground).


This should NOT be a CC ESC issue.....period.

Charlie, with all respect, I said all this in my question. (Answered in your quote.) I am C/C's fan, Joe Ford from early Kyosho Landmax days. Don't confuse my 6 posts with being a newbie.

The MMP arms with stock servo fine. It is either a deadband issue with the servo/MMP or something I don't know. Possibly the radio, DX3C. I don't have a Hitec servo programe box.

Regards,
Pete

[pyroM!KE]

Im running the same setup with the cc bec soldered to the main battery deans connector..Mine works fine..Try putting a different servo on there and see if it works..Any servo really..If it does the same thing its probably a bad rx..

[hoghead5150]

don't know much, but this happened to me. on my wraith, stock servo worked fine with mmp, jr servo didn't. what i forgot was to pull the red wire out of the esc plug going to reciever. mine was wired per castle instructions (except i forgot to pull wire!). had exact same symptoms you describe.

now buddy wired his servo up direct to bec, his glitched bad until he ran black/brown wire from servo to reciever also. the stock axial servo did not require this to work.

[Charlie-III]

Originally Posted by 10x8

Charlie, with all respect, I said all this in my question. (Answered in your quote.) I am C/C's fan, Joe Ford from early Kyosho Landmax days. Don't confuse my 6 posts with being a newbie.

The MMP arms with stock servo fine. It is either a deadband issue with the servo/MMP or something I don't know. Possibly the radio, DX3C. I don't have a Hitec servo programe box.

Regards,
Pete

Hi Pete,

Not saying you were a new guy....... just typical questions. Frankly, I can't remember seeing an issue with any servo on any CC ESC before (at least, while it's just arming the ESC....bind is different).

I, and my son, run/have run multiple CC ESC's with a variety of servos, most are HiTec. Never did anything special....plug them in, power them up, calibrate the ESC to the RX.

When you state "binded fine" is that TX to RX, RX to ESC (usually stated as calibrated) or both?

[10x8]

Originally Posted by Charlie-III

Hi Pete,

When you state "binded fine" is that TX to RX, RX to ESC (usually stated as calibrated) or both?

Charlie, no problem. I'm just getting frustrated now. It's usually pish easy setting this up.

Binding TX - RX ok, RX - esc ok. I have all the right lights on the MMP.

I'll be calm and try all night no worries. I hope to get it.

Regards,

Pete

[10x8]

Originally Posted by pyroM!KE

Im running the same setup with the cc bec soldered to the main battery deans connector..Mine works fine..Try putting a different servo on there and see if it works..Any servo really..If it does the same thing its probably a bad rx..

Stock AS-3 digital works fine, as said in 1st post. Thanks though.

Originally Posted by hoghead5150

don't know much, but this happened to me. on my wraith, stock servo worked fine with mmp, jr servo didn't. what i forgot was to pull the red wire out of the esc plug going to reciever. mine was wired per castle instructions (except i forgot to pull wire!). had exact same symptoms you describe.

now buddy wired his servo up direct to bec, his glitched bad until he ran black/brown wire from servo to reciever also. the stock axial servo did not require this to work.

Yep, covered. Sometimes I forget to plug the esc into the rx after progamming, lol. Thanks again.

[pyroM!KE]

[QUOTE=10x8;3611603]Stock AS-3 digital works fine, as said in 1st post. Thanks though.
Something is jacked up in your servo then..

[SuperRoo]

As a few others have said, it doesn't sound like a MMP problem.

Your replies also are a little confusing as you keep saying you covered it in the first post. You mentioned you tried another radio the Axial AR-3 RX & not said which esc? Axial or MMP?

If not with the MMP then maybe try the Axial AR-3 RX with the MMP.

Given that this is about a Hitec servo and a Spektrum radio then I would look at the 7955 and radio again as the possible culprit. A couple of issues that come to mind is the low frame rate (16.5ms) and low resolution (<1024) of the DX3C with a high resolution 7955 servo. Reprogram the 7955 for normal/low (1024) resolution and try again or try a standard digital Hitec servo.

The reason the Axial servo works with the MMP/Spektrum setup is because of the low resolution of the Axial servo.
The High resolution of the Hitec servo is 2048 and when used with a low resolution radio (1024 or lower) it can cause the issues your having, rx dropping out (digital interference) and the servo hunting for the correct center point. You may also find that the 7955 gets warm after trying to get it to work with the combination.

[Nova's Ark]

This is a common problem with the MMP. The MMP BEC is very weak! Just because you can program the voltage, doesn't mean it has the amperage to supply what you need. This is one of the reasons why Castle makes the MMP ONE CELL.

You need an external BEC with your MMP.

I know this from experience. I had to add BEC's to MMP because the high torque servos and winches would cause the ESC to shut down, reset, and re-arm. That is what your Spektrum RX is telling you when the green light is flashing like that. It has timed out because of a voltage loss. Spektrum makes a capacitor that will help with this problem, but in your case it will not fix it.

The cap is:

Spektrum Voltage Protector [SPM1600] | Radios & Accessories - A Main Hobbies

This is why your crappy Axial servo will work and your high end, big amp drawing servo will not. It's supply and demand in terms of voltage. High end electronics need more power to perform. The stock crappy servo does not. There is not an ESC on the market with a built in BEC that will outperform a stand alone CC BEC. Every single crawler I own has a CC BEC. Even some of my go fast RC's do.

The ESC has to burn off the voltage from whatever you are running (in my case 4S lipo which is 16Volts of the charger) down to 6.0 volts or less. That creates heat in the ESC. It has to cut that voltage down for the RX & servo some how. When you add a CC BEC and remove the small red wire from the ESC RX lead, it turns the internal BEC off. You will notice cooler operating temperatures, increased run time, and better performance.

[Scattman]

His 1st post says that he has a CC BEC.







Do you have the BEC directly powering the servo or is it running through the reciever? I had a similar problem with a spectrum rec and 7955 with a Castle ESC, I ended up wiring the servo straight to the BEC and let the ESC's internal bec power the reciever to fix my issues.

[10x8]

Originally Posted by SuperRoo

As a few others have said, it doesn't sound like a MMP problem.

Your replies also are a little confusing as you keep saying you covered it in the first post. You mentioned you tried another radio the Axial AR-3 RX & not said which esc? Axial or MMP?

If not with the MMP then maybe try the Axial AR-3 RX with the MMP.

Given that this is about a Hitec servo and a Spektrum radio then I would look at the 7955 and radio again as the possible culprit. A couple of issues that come to mind is the low frame rate (16.5ms) and low resolution (<1024) of the DX3C with a high resolution 7955 servo. Reprogram the 7955 for normal/low (1024) resolution and try again or try a standard digital Hitec servo.

The reason the Axial servo works with the MMP/Spektrum setup is because of the low resolution of the Axial servo.
The High resolution of the Hitec servo is 2048 and when used with a low resolution radio (1024 or lower) it can cause the issues your having, rx dropping out (digital interference) and the servo hunting for the correct center point. You may also find that the 7955 gets warm after trying to get it to work with the combination.

Thanks SuperRoo,

I'll ask the guys at work if they have the HiTec Program box. Anyway, I removed the MR3000 from my ship and will use that for the time being. It works fine with the 7955 & DX3C. It's resolution says 1024 as well?

Thanks again,
Regards
Pete

[The Violator]

I had some really weird issues with a sidewinder and external BEC in my daughters SC truck. It would jitter and jump but not go. Roll the firmware back on the MMP to the oldest one on your MMP. It was like there was some kind of feedback. I never updated any of my MMP's for this reason.

[10x8]

Originally Posted by The Violator

I had some really weird issues with a sidewinder and external BEC in my daughters SC truck. It would jitter and jump but not go. Roll the firmware back on the MMP to the oldest one on your MMP. It was like there was some kind of feedback. I never updated any of my MMP's for this reason.

Thanks Violator. Didn't think of that. I do have the latest version on the MMP.

I've got the truck all back together now, but I'll try it later. Sort of sick of taking battery tray off, removing lid etc. I got a mail slip today, which should be my order from Tower for one of those C/C quick link connect.

Take care,
Regards
Pete

[rjsl59]

i had a similar issue with the dx3c, i tried everything. i reset the radio to factory settings and that seemed to solve the problem, had to reprogram everything and it seems ok still.

[10x8]

Originally Posted by Scattman

His 1st post says that he has a CC BEC.







Do you have the BEC directly powering the servo or is it running through the reciever? I had a similar problem with a spectrum rec and 7955 with a Castle ESC, I ended up wiring the servo straight to the BEC and let the ESC's internal bec power the reciever to fix my issues.

Bec is wired to MMP. One day I might try bec to servo. Too lazy ATM.

Originally Posted by rjsl59

i had a similar issue with the dx3c, i tried everything. i reset the radio to factory settings and that seemed to solve the problem, had to reprogram everything and it seems ok still.

Sweet, I'll give it a go, thanks.

Pete