Spektrum Rx voltage prob w/ Futaba RX

[Gee]

I'm starting to run into problems with my futaba 4pk & rs603ff rx. It keeps shutting down like the RX pack is low. The packs I am using are fine and fully charged. I do have 2 Futaba brushless servos for the steering and throttle. I guess they are pretty power hungry. I bypassed the switch and the problem still existed. I run a 2s lipo rx pack & UBEC in the savage XL with a Futaba rs604ff, but in the truggy the space is limited for running a BEC.

I heard rumors that the Spektrum sr3xxx rx can handle up to 9volts. Anyone know if this is true? It would be nice to run a lipo pack in there without a bec. Can a 2s rx lipo pack be used with the spektrum rx without a bec? Does it drop the voltage down for the servos?

[Gee]

Well for those that had the same thought on this. I talked with a rep of Horizon Hobby (Spektrum) and the receiver can handle the voltage with no problems. The problem is the servos don't like more the 6v and the receiver isn't a BEC or regulator for the voltage.


Just curious if anyone is aware of a servo(s) that are rated for a 8.4 - 9vs? The most I have found in the breif search I did was the Hex Servo is rate for 7v per the specs at HC. The others either don't state the max volts only the specs for 4.8v and 6.0v speed and torque.

[What's_nitro?]

JR has some new HV models out that can take power directly from a 2s pack. Kinda pricey, but worth checking into since you've got ~$300 in servos anyways...

[jayjay283]

JR really stepped up and gave us what we need/want. No B.S. 7.2v right into the puppy. The price is a kick in the leg but they have a pretty good warranty too. Now if you others would stop pussy footing hows that 10s monster coming along

[eovnu87435ds]

whever I need to do any sort of Rx testing, etc outside of my vehicle, i have been able to power it with a 2s pack, and run my standard 6v servos. I have done it with the crappy duratrax and futaba s3003 servos, as well as my airtronics 94357, and they both run just fine on 2s. and thats with an sr3000 rx.I guess its up to you to see if it will fry your servo or not, but the ones i tested work. In other news, a quick google search found me these:

http://www.readyheli.com/Hitec_HS_79...V_p/37940s.htm

http://www.espritmodel.com/index.asp...OD&ProdID=8942

http://www.pilzers.net/index.php?mai...&products_id=3

http://www.jrradios.com/Products/Tec...dID=JRPS8711HV

[Gee]

Originally Posted by What's_nitro?

JR has some new HV models out that can take power directly from a 2s pack. Kinda pricey, but worth checking into since you've got ~$300 in servos anyways...

It not everyday you get a good deal on servors but it's the $300 dollars to replace the servos is what is scaring me. They do like to suck it out of a rx battery pack it seems like. Might be the combo of the reciever and the two brushless servos that make it seem to use up a rx pack faster. Did you notice any runtime difference using them with your brushless setups?

Originally Posted by jayjay283

JR really stepped up and gave us what we need/want. No B.S. 7.2v right into the puppy. The price is a kick in the leg but they have a pretty good warranty too. Now if you others would stop pussy footing hows that 10s monster coming along

Jayjay it looks like the 16yr old balding member has a pair. Let's see where he got them from.

Originally Posted by eovnu87435ds

whever I need to do any sort of Rx testing, etc outside of my vehicle, i have been able to power it with a 2s pack, and run my standard 6v servos. I have done it with the crappy duratrax and futaba s3003 servos, as well as my airtronics 94357, and they both run just fine on 2s. and thats with an sr3000 rx.I guess its up to you to see if it will fry your servo or not, but the ones i tested work. In other news, a quick google search found me these:

http://www.readyheli.com/Hitec_HS_79...V_p/37940s.htm

http://www.espritmodel.com/index.asp...OD&ProdID=8942

http://www.pilzers.net/index.php?mai...&products_id=3

http://www.jrradios.com/Products/Tec...dID=JRPS8711HV

I may try it out on some of my more expendable servos but it is going to be tough to test this realtime with servo that costs more to replace. Even if I did get them half price. You remember when you tested the servos was the battery off the charger (8.4v) or was it closer to the 7.4v. I would guess the servos listed for 7.4v take into account the voltage that the 2s lipo is really charged to. Don't you think?

Thanks for the links! The $420 Pilzers is a bit out the ball parks for me. Never owned a JR Servo but the specs are impressive. The HiTec servo has decent enough specs and is getting closer to the $ range of the working man. A .06sec steering servo is going to need a Tx that can slow that baby down for me.




These servos are rated at 7.0v and seem to be a good canidate ($8.00)to test the 2s lipo with.

http://www.hobbycity.com/hobbycity/s..._10kg_/_.16sec

Here are the specs and a review from a HC member.

size: 40mm*38mm*20mm
weight: 48g
speed (4.8v): 0.17sec/60degrees
speed (6.0v): 0.13sec/60degrees
stall torque(4.8v): 13kg/cm
stall torque(6.0v): 15kg/cm

Electrical measurements done :
@4.8V
Idle current below 20 mA
Average current 650 mA
Stall Current 1300 mA

@6V
Idle current below 20 mA
Average current 1000 mA
Stall Current 2000 mA

Those are measurement data and cannot be considered as specification.

These servo are requesting high current. So please use correct power supply to power them. A 3A BEC cannot power more than 2/3 of these servo without danger.
Use 8A BEC instead, see Assan BIG BOSS 1 UBEC 8-12A.

For anyone that speaks or understands the electrical measurements jargon.
Can you interpret for me what that might mean if a 7.4 lipo for a st & th setup?

[What's_nitro?]

Originally Posted by Gee

..... Did you notice any runtime difference using them with your brushless setups?

I did not. Honestly, I doubt it would be noticeable unless you were a very consistent driver.

[eovnu87435ds]

I am a bit OCD about keeping my lipos fully charged. It was fresh off the charger, I slipped the wires from a servo lead between the clips on the deans(dangerous, mabye, but i needed to test something.), and plugged it in. works fine. also, i stripped some laptop batteries and made it into a 2s3p rx pack for the barbie jeep. fully charged at 8.4v, and it currently only powers the rx and a duratrax servo that is used to remotely turn the headlights on and off. It handles the current just fine! I would assume it would be more like putting a 9v battery into an xmods car, instead of the regular 6. electronics handle fine, gears not so much. for anything with a practical use, like steering, as long as you have metal gears you should be fine.