Spektrum receiver brown out?

[badger5]

Yesterday when running my 1/8th electric buggy I was having problems with what I thought was interference, but later found out the receiver was dropping out and then having to reboot.
My set up is 4S with Tekin RX8 ESC, Spektrum SR3500 receiver with DX3C tx and Savox 1256 steering servo.
I tested it in the pits and found that even with no throttle being applied the steering servo would work ok and then intermittently cut out, later on I also confirmed that the orange LED on the receiver was also going out when the steering servo didn't work. This even happened when the car was on a stand and thus no load for the servo.
Once back home I tried the Serpent with a less powerful servo (Savox 0254) and this was ok. I then tried the 1256 servo in my 410 that has the same type of Spektrum receiver and an Orca Vritra ESC, and this had the same issues with the receiver browning out.

I know that problems with Spektrum kit and Savox servos are well documented but the 1256 is a fairly normal servo that it's 57 and 58 cousins are routinely used in 1/10th.

So first question, would the current draw from the servo be the same with or without load on the steering wheels? My thinking it should be less but then why should I be having these issues even when the front wheels are off the ground? Could the servo be at fault?
Secondly would a glitch buster solve my problems? Of not then will I be looking at having to replace my radio set up?

[RICHARD OXLEY]

can you adjust the bec voltage on the speedo?

[mattybucks]

The servo is drawing to much current causing the receiver voltage to drop/reset. Try running a power cap on the receiver. Another issue with this typre of problem is your PT light with also drop out.

[SlowOne]

Spektrum/Tekin/Savox brown outs are a known issue. Even in 12th scale with low loads most people have given up on this system and go with Futaba or Sanwa 2.4 systems for reliability with Hobbywing and LRP speedos. (Note, in 12th we don't use Savox because the output spindle is in the wrong place.)

Spektrum receivers, Savox servos and Tekin speedos are involved in too many of these enquiries for it to be a co-incidence. With the tolerances on the electronic components in the servo, receiver and speedo, it is entirely possible that some set-ups get little or no problems, and others have or develop problems. If you trawl the forums you will find a lot of enquiries of this type that mention Savox, Spektrum and Tekin. I've yet to see any involving Futaba, LRP, Hobbywing or Sanwa.

By all means try the glitch-buster capacitor in the receiver, but for a true diagnosis you need to attach all your stuff to a Futaba or Sanwa 2.4 system and see what happens. I am not dissing any of these products (used them all myself at one time, except the Savox) just letting you know that the combo you have is often cited by users on forums as having these issues... eventually. HTH

[badger5]

Thanks for all of the responses, now just to clear up some questions. The BEC output from the RX8 is set to 6V but is rated at 5A so I thought that this should be strong enough. The HW based 1/8th ESC are rated at 3A and have known to have given issues. Maybe ESCs in the future will have adjustable BEC voltage outputs, it seems that with more people using HV servos this would be a good move. I think the problems seen on Tekin ESCs BEC is from the RS range.
To me it almost seems that the receiver is throttling the current throughput possibly with a higher internal resistance.
It's looking like I will either really have to change radio system or servo, and possibly both. Any recommendations for a good servo for 1/8th off road steering?

[eyeayen]

Hitec 7945TH are what Jon Hazelwood uses and really rates them, a few of the other Agama drivers have followed and love them.

That said someone else I know had problems with them, not just once so has gone to a helicopter servo MKS DS670.

The Ace DS1015 ( also rebadged as Associated XP DS1015 ) are good.

Futaba have been used by nearly everyone who competes at a serious level but sorry I don't have any numbers for those. I've got some BLS351 's but I don't know if these have been replaced by a new model ?

Sanwa and KO are meant to be good as well but again I can't supply you with any info on them, sorry.

[badger5]

I've fitted a glitch buster and, for now all seems good with the receiver seemingly rock steady and no more brown outs.
It does seem that Savox servos draw quite a bit of current, not sure if this is because many of them are quite high rated for torque or they are just inefficient when compared to others.
I'm still going to look into upgrading my radio set up and servo at some point, but it will be interesting if this cheap fix actually works on track and lasts.
Thanks everyone for all the help and advice, greatly appreciated.

[metalmickey0]

Originally Posted by badger5

I've fitted a glitch buster and, for now all seems good with the receiver seemingly rock steady and no more brown outs.
It does seem that Savox servos draw quite a bit of current, not sure if this is because many of them are quite high rated for torque or they are just inefficient when compared to others.
I'm still going to look into upgrading my radio set up and servo at some point, but it will be interesting if this cheap fix actually works on track and lasts.
Thanks everyone for all the help and advice, greatly appreciated.

Dont bother changing your radio as its not that. i had the same problem running a Savox servo in my B4, and same again when put it in my crawler. So changed the servo to Hitec and now the problem has gone. So wont be using savox servos anymore.

[Gnarly Old Dog]

Originally Posted by badger5

I'm still going to look into upgrading my radio set up and servo at some point, but it will be interesting if this cheap fix actually works on track and lasts.

Glitch Busters / Power Caps can be pretty effective at making a marginal setup work ok but before you change your radio, you might want to think about the Spektrum SR3100 DSM2 receiver - or the SR3520 Micro DSM2 Rx.
Since you mention that you have the DX3C transmitter, according to the Spektrum website (www.spektrumrc.com) you should be able to use the DSM2 range of receivers which module / stick owners have never been able to do (surface Spektrum modules are not DSM2 compatible)

One (of the many) advantages with the newer DSM2 modulation is that in general, the receivers seem less prone (or should that be more tolerant?) to the brown-out / low instantaneous voltage drops that can affect the earlier DSM micro Rx's like your SR3500. DSM2 can also offer faster re-bind and the modulation method is more robust since it transmits on 2 separate channels simultaneously - so if one gets momentarily hit on by an FHSS system as they hop around, it can still decipher the signal state from the Tx on the other channel - meaning that the Rx doesn't have to wait until a clean signal is received again - thus it is more robust against the effects of a 'noisy' 2.4GHz bandwidth.

Failing that - I can thoroughly recommend the Spektrum DX3R Pro

[RogerM]

Originally Posted by Gnarly Old Dog

you should be able to use the DSM2 range of receivers which module / stick owners have never been able to do (surface Spektrum modules are not DSM2 compatible)

Is there any plan to do something about that?

I have been a very big fan of the Spektrum stuff since it came out and have used it in both a 3VC and my current KO Universe BUT I'd really like to go to the DSM2 style system for the reasons you mention but can not run a steerwheel (more than 25 years of sticks just make the switch impractical).

[Gnarly Old Dog]

Originally Posted by RogerM

Is there any plan to do something about that?

I'm sorry I'm not able to answer you on that one.

[atsang]

Hi guys ive also had a similar problem only its the speedo cutting out... Im using a spektrum micro reciever and a savox 1251 servo... sometimes the power just cuts out by itself although i cant tell if the orange light is cutting out because it only seems to happen when its running... any ideas???

[badger5]

When the power cuts out do you still have steering? And what ESC do you have.

[atsang]

Yea still have steering and ive had 3 speedos in a losi xcellron lrp spx and lrp sphere all do the same thing...

[RICHARD OXLEY]

i run 2 futaba 9452 servos with a spektrum micro rx in nitro car
i can stall both servos and the rx will not brown out. the servos
are only rated at about 9kg but always found this plenty in rallycross
for steering and brakes.