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Old 10-02-2010, 06:47 PM   #151
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yeah i run a couple of 18500 18x50mm (AAs are 14x50mm 14500) li-ions in my rascal 2 rx pack.

those in that mod are 18650 18x65mm 2400mah cells, think mine are 1600, AA size li-ions are about 900mah
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Old 10-02-2010, 08:13 PM   #152
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Just bought one. Couldn't resist $6 RX, wish it had more model memory though... I guess I have a bit of a wait now from HK.. lol
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Old 10-03-2010, 04:50 PM   #153
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i'd like to see someone try to operate this radio with a 2s lipo or other pack down at that sort of volts range
I got one of these 3s packs and modded my GT3b to accept it. Works great. Just took out the 3 lowest screws and pried the base apart enough to pull out the battery holder. Crimped a servo connector on to the wires and it's perfect. Hardly worth the trouble of doing anything more complicated with small lipos being so cheap.
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Old 10-03-2010, 07:22 PM   #154
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Yeah, a 3s lipo will "work".. but i've been looking at a lot of info regarding battery mods just lately and applying my electronic knowledge.. a few people have damaged radios (not this particular model) by having them on for long periods of time without allowing them cool-down time. Fact is 2.4ghz radios most of them just do not need 11-12v and it shortens the life of the tx by giving them it... i think it was on here i read about JR or airtronics saying 3s lipo is definitely not recommended for their tx's as they're designed to use 9.6v 8xAA packs

I'm working on two possible solutions to this problem:

1: fool the low voltage protection circuit into thinking it has a 8xAA alkaline pack in it, whilst fitting a 2s lipo (7.4v) or 8 NiMH cells - the low volt alarm on these is supposed to be at 9v - at which voltage 8xAA NiMHs are only about half discharged

2: replace the offending part that burns out (transmit circuitry voltage regulator) with a more efficient, better one which doesn't get warm never mind hot, has less parasitic power loss, etc so that one can run virtually any battery one likes. this would keep the low volt alarm at 9v which is perfect for a 3s lipo.

of the two i unofficially prefer option 2 - it will be less likely to cause problems with other parts of the TX, and is better for when the batteries go flat - the 6v flat of a 2s pack is really pushing it and may cause issues with operation. The first option is cheaper (one resistor) but means the voltage display will always read wrong. Option 2 actually should increase battery life - the mod i'm talking about is known for spektrum DX radios and doubles their runtime.

I love this forum, i've got a lot of in-depth tech from it that i just haven't seen anywhere else.. but in that respect even this forum is barren compared to flyboy forums. RC plane guys seem to be much more into custom electronics and tweaks than us car guys who seem to be much more interested in plug-n-play electronics. I wouldn't be happy playing around with a several hundred KO/JR/Futaba but on a 40 radio like the GT3B it's worth it to get a completely bombproof radio whilst i'm invalidating the warranty by adding extra LEDs, messing about with the battery box anyway. I'd consider it my contribution to the world 2010/2011 to do a nice mod guide for this and other ideas.

EDIT: now that i think about it, the mod i looked at earlier fits a 3.3v reg into a tx.. which is perfect volts for ultrabright blue leds IIRC - cuts a component or two out of my idea for a backlight mod
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Old 10-03-2010, 10:07 PM   #155
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Hello,

I'm hoping to save my self from looking like a fool here then if were not talking abot the same radio. However, the radio I'm ref to is that with the flat lcd/digital face similar to of the airtronics mx11 but less the fancy plastic moldings and other fabrications and whistles it offers. All or both are sanwa based or as we say, airtonics. If this is not the radio in discussion then please forgive me for my assistance here. However, I think we are all on the same page about the FS GT3B "flysky digital upright faced radio".


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Old 10-03-2010, 11:07 PM   #156
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Yeah we are on about the FS-GT3B.. and it does look sort of like the m11 without the carry handle.. your previous post was a little confuddlin'

wow wouldn't that be something if this was a clone of a sanwa set

very interested to learn a few people from your club have this set.. they experience no glitches when run with other radios? in particular the GT2 as that used to make the old GT3 a bit twitchy when they were used together.. anyone there also use the FS-GT2?
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Old 10-04-2010, 12:30 AM   #157
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very interested to learn a few people from your club have this set.. they experience no glitches when run with other radios? in particular the GT2 as that used to make the old GT3 a bit twitchy when they were used together.. anyone there also use the FS-GT2?
I ran mine over the weekend together with a GT2 and a few futabas 4PK and the GT3B performed flawlessly without glitches and the range was awesome. You can go as far until you cannot hear your nitro engine anymore or your model disappears.

The problem I still have is the unequal throw of the steering servo, otherwise I am very happy with this set
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Old 10-04-2010, 08:32 AM   #158
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petrolhd that sounds like an issue with your individual tx.. other people haven't mentioned it.. could be something you could get around with settings but like i say sounds like a fault with the one you have
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Old 10-04-2010, 09:12 AM   #159
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petrolhd that sounds like an issue with your individual tx.. other people haven't mentioned it.. could be something you could get around with settings but like i say sounds like a fault with the one you have
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Old 10-04-2010, 05:23 PM   #160
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Yeah, a 3s lipo will "work".. but i've been looking at a lot of info regarding battery mods just lately and applying my electronic knowledge.. a few people have damaged radios (not this particular model) by having them on for long periods of time without allowing them cool-down time. Fact is 2.4ghz radios most of them just do not need 11-12v and it shortens the life of the tx by giving them it... i think it was on here i read about JR or airtronics saying 3s lipo is definitely not recommended for their tx's as they're designed to use 9.6v 8xAA packs

I'm working on two possible solutions to this problem:

1: fool the low voltage protection circuit into thinking it has a 8xAA alkaline pack in it, whilst fitting a 2s lipo (7.4v) or 8 NiMH cells - the low volt alarm on these is supposed to be at 9v - at which voltage 8xAA NiMHs are only about half discharged

2: replace the offending part that burns out (transmit circuitry voltage regulator) with a more efficient, better one which doesn't get warm never mind hot, has less parasitic power loss, etc so that one can run virtually any battery one likes. this would keep the low volt alarm at 9v which is perfect for a 3s lipo.

of the two i unofficially prefer option 2 - it will be less likely to cause problems with other parts of the TX, and is better for when the batteries go flat - the 6v flat of a 2s pack is really pushing it and may cause issues with operation. The first option is cheaper (one resistor) but means the voltage display will always read wrong. Option 2 actually should increase battery life - the mod i'm talking about is known for spektrum DX radios and doubles their runtime.

I love this forum, i've got a lot of in-depth tech from it that i just haven't seen anywhere else.. but in that respect even this forum is barren compared to flyboy forums. RC plane guys seem to be much more into custom electronics and tweaks than us car guys who seem to be much more interested in plug-n-play electronics. I wouldn't be happy playing around with a several hundred KO/JR/Futaba but on a 40 radio like the GT3B it's worth it to get a completely bombproof radio whilst i'm invalidating the warranty by adding extra LEDs, messing about with the battery box anyway. I'd consider it my contribution to the world 2010/2011 to do a nice mod guide for this and other ideas.

EDIT: now that i think about it, the mod i looked at earlier fits a 3.3v reg into a tx.. which is perfect volts for ultrabright blue leds IIRC - cuts a component or two out of my idea for a backlight mod

I don't think a 3S Lipo should be a problem because the radio is designed to run on AA alkaline batteries aswell as rechargeables. Fresh alkaline batteries are usually ~1.6v each so 1.6*8= 12.8. A lipo cell's MAX voltage is 4.2v, so 3*4.2= 12.6. I've been running 3S lipos in my Futaba 2pl without a problem.
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Old 10-04-2010, 05:50 PM   #161
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I don't think a 3S Lipo should be a problem because the radio is designed to run on AA alkaline batteries aswell as rechargeables. Fresh alkaline batteries are usually ~1.6v each so 1.6*8= 12.8. A lipo cell's MAX voltage is 4.2v, so 3*4.2= 12.6. I've been running 3S lipos in my Futaba 2pl without a problem.
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Old 10-04-2010, 06:46 PM   #162
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2.4ghz electronics is 3.3 or 5v. the radios have regulators in them to step down the 12v of the batteries to the voltage the transmitter part runs on

this mod for the DX6 (8xAA) shows it http://www.dimensionengineering.com/...ektrum_mod.htm

so yes, they're designed to run on 12v but little cheap linear voltage regulators get really hot dissipating that much voltage (8.7v). They also waste a tremendous amount of power as heat - which means you get less runtime - and this is for a spektrum radio never mind a cheapie. these radios have closed cases and no heatsinks on the regulators which is a recipe for burned silicon.

What this means is you will be ok running the radio (this applies to all 8xAA radios not just the GT3B) as long as you dont run it for hours on end, you'll be giving the regulator cool down time before it gets into thermal runaway.. but i keep seeing threads "i left my radio on accidentally and now even with new batteries i have no range"

the reason they get no range is their regulator has partially burned out and no longer supplies the correct votage to the transmit part of the circuitry.

it's possible being a high end radio that the futaba 2pl has proper regulation. More likely you don't run it for hours and hours.

It's also very likely I am falling into the engineer's failing of overengineering everything. I have a habit of doing that. Thought it would be useful info for the folks here, especially those who (like me) do not like LiPo tech, or for one reason or another don't run it.. my electric cars run LiFe or NiMH batteries, i have Li-Ions in my nitro, soon to be upgraded when i can figure out where to fit them, to LiFe... i'm torn between using 3s LiFe or 9s NiMH (eneloop) for my GT3B.. will need the power saving of a proper regulator if i run LiFe as the cells that fit are only 1100mah and i do run for hours on end.. often running my electrics till all my packs are flat, then getting the nitro started
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Old 10-04-2010, 10:28 PM   #163
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I got my Gtb3 on saturday from wellqin. Today I put some batteries in it. From what I have seen so far I'm very happy with this radio especially since it was only $68 shipped from china.

The looks of the Gtb3 are great though I don't quiet like the chrome wheel. The receiver as most know is very small and thin. So it will easily fit in any car.

As many have stated the backlight is hard to see in the light and when the backlight turns off you can only see the model and the voltage. To me this isn't a huge deal because I will most likely set-up my cars in my workshop and leave them set-up that way but a upgrade to the back light would be nice.

For me the radio fits good in my hand and I don't think it feels cheap. The wheel is slightly wobbly but it is not noticeable when using the radio only when you yank on it a bit. The only parts that feel cheap and wierd are the Ch3 trim and the dual rate buttons that are where your thumb goes. This isn't a big deal as they still work and if you don't like using them you can access those adjustments thru the menu

As far as the interface goes I popped the manual disc into my computer to check it out and after checking to if it works I didn't have to look back at the manual at all. The radio is very easy to use and easy to set-up and get around the menu's.

A major concern I had was when I heard about the weird trim and range of motion for the steering. I have yet to come into a problem with either of those things. The car I am using is a B4 and to take advantage of the full range of motion available on the car I only had to use about 90% out of 120% on the end points on each side. To test the range of motion outside of a car I set up a servo with a servo horn on it and set the endpoints to 120% and watched the range of motion. I then took an old am radio I had laying around and did the same test with it. There wasn't a noticeable difference at all between the old AM radio and the GT3B as far as range of motion goes. So from what I have found I think the Gt3B has the standard amount of range of motion.

So far from what I have see and tested.. This radio can't be beat. Others have done farther tests and can vouch for the range of the radio which I have heard is great. Basically for somewhere around $65-70 (including shipping) you get a good radio that has alot of features and 10 model memory. The radio looks good and the best part is the receivers are $6-7. For a budget racer or a basher I recommend this radio and I also recommend wellqin as a seller of the radio.
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Old 10-05-2010, 06:31 AM   #164
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Hi Eds24,
A major concern I had was when I heard about the weird trim and range of motion for the steering. I have yet to come into a problem with either of those things. The car I am using is a B4 and to take advantage of the full range of motion available on the car I only had to use about 90% out of 120% on the end points on each side. To test the range of motion outside of a car I set up a servo with a servo horn on it and set the endpoints to 120% and watched the range of motion. I then took an old am radio I had laying around and did the same test with it. There wasn't a noticeable difference at all between the old AM radio and the GT3B as far as range of motion goes. So from what I have found I think the Gt3B has the standard amount of range of motion.
After reading all the glowing reports, I am beginning to think that there is a problem with the endpoint adjustments on CH1 of my TX.

As described in page 17 of the manual, to adjust the endpoints, one needs to turn the steering wheel left for the left/forward arrow to appear and similarly turn the steering wheel right for the right/back arrow to appear so that the respective endpoints could be adjusted.

In my case, the right/back arrow appears when the steering wheel is held to the right and it jumps right back to the left/forward arrow when the steering is released at center position. Is this the normal behavior of the endpoint adjustments for CH 1 ? Now, adjusting the right endpoint requires 2 hands, one to hold the steering to the right and the other to turn the enter wheel.

This issue could be contributing to my problem of unequal steering travel of the servo.

With CH 2 and 3, the left/forward and right/back arrows can be toggled by moving the controls in the respective direction.

Thanks
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Old 10-05-2010, 11:24 AM   #165
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After reading all the glowing reports, I am beginning to think that there is a problem with the endpoint adjustments on CH1 of my TX.

As described in page 17 of the manual, to adjust the endpoints, one needs to turn the steering wheel left for the left/forward arrow to appear and similarly turn the steering wheel right for the right/back arrow to appear so that the respective endpoints could be adjusted.

In my case, the right/back arrow appears when the steering wheel is held to the right and it jumps right back to the left/forward arrow when the steering is released at center position. Is this the normal behavior of the endpoint adjustments for CH 1 ? Now, adjusting the right endpoint requires 2 hands, one to hold the steering to the right and the other to turn the enter wheel.

This issue could be contributing to my problem of unequal steering travel of the servo.

With CH 2 and 3, the left/forward and right/back arrows can be toggled by moving the controls in the respective direction.

Thanks
Yes it is normal for the left/forward to show when the steering wheel is at neutral and yes you do have to use two hands to adjust the endpoints. One to turn the wheel to the left/right and the other to move the dial. Not sure why your having unequal travel.
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