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Old 07-04-2014
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Default fitting bigger capacitor to tekin rs pro? or glitch elsewhere

hi fellas i have just put a 2nd hand tekin rs pro in my xb4 however i found that yesterday it was glitching with my savox servo an the reciever ( spectrum) was flickering on an off. endpoints are set corrctly as well
i tried 2 recievers and it still did it . i had tested the tekin in my drift car beforehand and it was fine working order
then i added a capacitor to the reciever ( glitch buster) which helped until the latter part of the race as the batteries lost a bit more charge and then about 4 min in to the race it would glitch again and turn off and on again
i thought it might be the savox but its pretty new and has worked fine for months
however on closer inspection this morning i found the little silver capacitor that comes with the esc had come away on 1 leg so was not connected so .......
1. could this be the source of the glitch or does it not make much differance , as i said the glitch happens when the batteries get to about 8 volts near the end of the race and while doing a lot of steering on throttle
2. i am going to replace this capacitor with a new one , but can i replace it with a larger one or 2 wired together to increase the capacity and help prevent it drainig as quickly under load
3. what capacity is reccomended for the power cap for the esc and for making a new glitch buster

thanks in advance
johnny
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Old 07-04-2014
shaine shaine is offline
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There has been loads written about this issue on a large U.S site.

From what i can gather Savox and Spektrum dont play well with certain ESC's due to a weak BEC. The Savox servos are said to draw a lot of current starving other components in the process.

I totally bypassed the savox servos when shopping because of this reason and went with a
Xpert RC SI-3401 Brushless Servo 12.47kg 0.080 Sec

which draws a lot less current.


Another option although more expensive is to change your radio gear in the hope that solves it.
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Old 07-04-2014
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Hi,

A savox will pull spikes of 3.5A which can upset weak BEC circuits causing the receiver to 'brown out' (glitch)

The capacitor on the speedcontroller is there to handle the ripple current so the large ripple is not seen by the cells, having this diconnected will cause high ripple in the cells which can cause the speedo to brown out.

So replace the cap/caps on the speedo, yes if you have space you can add 2 together.

This together with keeping the receiver capacitor should solve your problem.
I run spektrum and savox with 2200u 25V cap on the receiver (rubycon ZLH series I think) i'll check.
I have no issues with brown out on Durango 410. My speedo is a Nosram matirx which although is rated at 3A BEC, I know its good for 4A I tested it. Won't do 4A for long though I had it run 4A for 3 min continuous, it got a bit hot.
As for a speedo cap, I've used 1600u and 2200u and they have all been fine. but the bigger the better just make sure its at least 16V better if its 25V. use ones with low internal resistance Rubycon ZLH for example.
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Old 07-04-2014
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Right chaps, lets get some things straight from the get go...

The capacitor on the ESC is there to drive the FET gates open and shut and has nothing to do with 'ripple currents', trust me, I know having been involved in testing ESC's since the early 90's....

If the ESC is disconnected from the capacitor, it can cause drive issue's on the ESC side.

BEC circuit in the Tekin, it is has a high current rating.

Savox, this is where the crux lies, they are glitchy, noisey and hungry servo's which can AND DO cause brownouts. I have even had a small 12th Savox cause system shutdowns in a GT12 on 2S.

If you re-attached/replace the ESC capacitor, fitted a capacitor to one of the receiver ports, changed the receiver, I would then look at the servo, check for free movement etc.
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Old 07-04-2014
badger5 badger5 is offline
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As mentioned above Spektrum and Savox don't really seem to mix well, from my understanding it's caused by the Savox servo drawing higher currents than other servos and the Spektrum receivers having the failsafe voltage cut off set higher than Futaba or Sanwa. The RS Pro's weren't know to having the strongest BEC's either! I had the same issues with an 1/8th electric buggy then I switched to Futaba servos and Sanwa radio and never had an issue again.

For the Tekin speedo it does need a capacitor on it, Tekin mount it directly on the speedo as the shorter the wiring the better the effect it has, many people also mounted two caps on the RS Pro for 4wd trying to keep the speedo cooler.
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Old 07-04-2014
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thanks guys, thats all good advice , i will source some good caps and get soldering,
so 16v or 24v is fine and about 1800 to 2200 uf
ive generally run lrp speedos and savox servos where i could so this problem has been rare
i also have a low profile savox running on a reventon s and spectrum in my drift car and thing this may also need a cap making to,
im a bit gutted though i always liked savox servos ive had one 4 or 5 years now and its still spot on , and i also like spectrum radio gear
but maybe time to change servo brands
in the 4wd anyway
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Old 07-04-2014
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just to add another angle to this I've ran the RS ESC(not pro) in my dex210 and previously losi 22 with a Savox servo with NO cap on the ESC or reciever for
over 3 yrs now
with no problems at all,fitted wth KO receiver is the key point
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Old 07-04-2014
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If you can get a DSM2 Rx it also solves the Savöx/Spektrum issue.
Or at least, when i got a DSM2 Rx, the problem went away. With or without the glitch buster.
Theres no room in a 410 to run one really. So the DSM2 was an easier option. The Orange RX from Hobbyking do the job fine. I'm running two or three of them.

And as i've broken servos, all my Savöx have been retired, except the one in the 8th. But the BEC on that is a beast, so i'm not worried!
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Old 07-04-2014
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Quote:
Originally Posted by DCM View Post
The capacitor on the ESC is there to drive the FET gates open and shut and has nothing to do with 'ripple currents',
DCM all of your post is valid and correct, But I disagree here. You still need the caps on the ESC oh yes, What the purpose is can be open to debate. At the moment from the simulations i've done on brushless FET drive it looks and behaves like a ripple current filter. But i'm happy to educated otherwise by a convincing alternative.

But the main points here are the same..
Caps needed...yes
Savox power hungry...Hell yes.
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Old 07-04-2014
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Thanks guys the info is very helpful and may save me a fortune replacing gear and a headache
Mattr is this the receiver I need
http://bit.ly/1g1zuvJ
Hope so
It's a cheap fix to stay running with my current gear
That I'm quite happy with up till now
And on another note I was a bit worried about tekin esc s but I must say it felt really nice when it was going
Smooth and fast
But will it last
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Old 08-04-2014
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Quote:
Originally Posted by mpg200 View Post
DCM all of your post is valid and correct, But I disagree here. You still need the caps on the ESC oh yes, What the purpose is can be open to debate. At the moment from the simulations i've done on brushless FET drive it looks and behaves like a ripple current filter. But i'm happy to educated otherwise by a convincing alternative.

But the main points here are the same..
Caps needed...yes
Savox power hungry...Hell yes.
As you push power through a FET, it heats up, as we are driving the gates open and shut at a high rate, the heat builds up resistance which builds up heat. A battery, whether NiCd, NiMH or LiPO can't give that instantaneous burst to fire the gate side of the FET open or shut fast enough, a capacitor can, and the higher the quality, the better it works, hence why the capacitor is there, it makes the esc more powerful but what it does is make the FET work more efficiently.
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Old 08-04-2014
mattr mattr is offline
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Quote:
Originally Posted by johnnygibbon View Post
Mattr is this the receiver I need
http://bit.ly/1g1zuvJ
Hope so
No. That's slightly overkill!
http://tinyurl.com/plmzhyk
This is available in the UK warehouse, i usually buy two at a time. Or three. As they are cheap enough to just leave rattling around in your tool box in case of emergency.
Not sure how the DSM2 actually helps, i think it might just be better at holding onto the signal from the Tx.

And TBH, there are many many better servos out there, if (when?) you kill the savöx, have a look round for an alternative!
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Old 08-04-2014
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Quote:
Originally Posted by DCM View Post
As you push power through a FET, it heats up, as we are driving the gates open and shut at a high rate, the heat builds up resistance which builds up heat. A battery, whether NiCd, NiMH or LiPO can't give that instantaneous burst to fire the gate side of the FET open or shut fast enough, a capacitor can, and the higher the quality, the better it works, hence why the capacitor is there, it makes the esc more powerful but what it does is make the FET work more efficiently.
Not convinced.
For the majority of people it doesnt matter, you need caps on ESC power input.
The function I suppose is not for this thread so let's leave it.

On to orange RX DSM2 compatable recievers.. I have used the 3 ch ones and have had no problems
http://www.hobbyking.com/hobbyking/s...dProduct=23784

Smaller than spektrum and so far seem to be just as good, however I have only used them in micro applications with no serious servo loading.
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Old 08-04-2014
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DCM has it pretty spot on to be honest.
Yes this thread has gone a bit off topic but I thought I'd put some thoughts to what I've seen with those orange receivers and Spektrum. I've seen people try and use the hobbyking orange receivers in 1/10th off road and usually they have issues, only just last a couple of weeks ago one guy had to pull out of the meeting as his car kept losing control and he was using Spektrum radio with a hobbyking orange receiver, not sure if it was browning out or another issue but it ruined his day. All the peolple that use Sanwa or KO at our track very rarely have issues, expensive but very good and solid perfromance.
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Old 08-04-2014
mattr mattr is offline
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I'm running one in a 210, have run in a 410 (only came out as i dismantled another car that had a spare genuine spektrum fake in it) and one in a 410 that i've got set up as a 2wd. And another in a XB9e (savöx servo too) had no issues with any of them.

Until i plugged a connector in wrong and smoked a servo. But thats my problem, not the Rx.
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Old 08-04-2014
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well im bidding on a cheap orange one on ebay now it seems the cheapest fix
if that dont work then servo swap it is
im used to my dx3r now and i was gonna update to the pro version (2n hand of my mate)
so i hope these recievers and new caps solve the brown out issue
rippling fets sounds worrying as well
like a uncomfortable medical condition
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Old 08-04-2014
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Quote:
Originally Posted by mpg200 View Post
Not convinced.
For the majority of people it doesnt matter, you need caps on ESC power input.
The function I suppose is not for this thread so let's leave it.
Not convinced...? Let's leave it...?!!! I cannot believe that you can sit there and type that in the face of the correct science and description of the reason capacitors are attached to speedos, and why getting them as close as possible helps. Unbelievable...

To help the poster... Across a number of forms across the world, and especially in my class (12th circuit) both Spektrum and Savox are a common cause of interference issues. For every one person that has no issues, we see two that do. The strange thing is that a lot of people go for ages with no problem at all (that's me!) and then all hell breaks loose and it seems incurable.

12th cars are the most challenging on RC gear. I don't think it any coincidence that by the vast majority we use Futaba and Sanwa gear throughout.

I hope that the suggestions here get it fixed for you - it's arguably the most annoying problem in RC because when it strikes in anger, there seems no rhyme or reason for it, or for fixing it.
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Old 09-04-2014
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If you want some of them Orange RX receivers, I got 5, 4 are usable, one has a pin that's pulled out (when I removed a receiver wire), reason for not using, I got a Spektrum DX4S and decided to upgrade the firmware to the latest version and went from being able to use the orange receivers to not even being able to bind one. So, if you want some, very cheap (as they are no good to me or the kids) let me know.
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