DIY: Add Two More Channels to a JR Quattro Tx!

[Mr.RC-CAM]

I purchased a used JR Quattro 4-ch Tx from a fellow eZoner. I was curious to see what was inside, so I took a peek at the circuit board. I was surprised to see that it was begging to be hacked for two more channels.

Within a couple of hours of its arrival, mine sported a new gear switch and fully proportional Aux knob. My 4-ch Tx is now a manly 6-ch rig. I sure like those little Easter eggs that engineers leave in for us to find.

The mod involves adding a toggle switch, miniature pot, 2 caps, and a resistor. The board is SMT construction, so this is NOT a project for the average bear. I can nearly promise you that you will destroy your Tx if you do not have considerable SMT rework experience. If you know what you are doing then this mod will take less than an hour.

Here is the new Ch-5 switch and Ch-6 knob.

[Mr.RC-CAM]

The first thing to do is to add a .1uF 0805 SMT cap at location C26, per the photo below.

You might notice that two other new caps were installed (outlined in yellow) at C27 and C28. But, these are NOT required. So you can omit them.

[Mr.RC-CAM]

Next, you must remove a resistor, move a resistor, and add a new cap and resistor. Please refer to the photo below.


Remove the 0-ohm resistor at location R22. It is not used.
Move the 0-ohm resistor from location R8 to location R7.
Add a 1K 0805 SMT resistor at location R23.
Add a .1uF 0805 SMT cap at location C40.

[Mr.RC-CAM]

Next you must mount the SPST switch and a 5K to 10K pot. My parts came from my "junk" drawer so I do not have any part numbers. Both fit like a glove, so I was lucky.

By the way, they both mount in existing Tx case holes. The switch's hole is covered by a push-out plug (just pops out without a fuss). The pot will require that you cut a hole in the decorative decal on the face of the Tx (but the actual Tx case is ready to go).

[Mr.RC-CAM]

The CH-5 gear switch (SPST type) is wired to pcb location "CN5." The CH-6 Aux pot (5K to 10K) is wired to location "CN6."

The three pot wires are connected to the pot's three terminals in the same order as found on the PCB (outside to outside, center to center).

If you want CH-5 and CH-6 servo reversing, then add SPDT slide switches to the pcb locations marked "S5" and "S6." I did not need them so they were not installed in my Tx.

[Mr.RC-CAM]

That is all it takes. It is a very sweet (and cheap) upgrade to this low cost Tx. There is one more secrete trick that the Tx can do, but I won't talk about that hack unless I try it out first.

If you have questions about this hack please do NOT email or PM me. Instead, post your questions or comments to this thread.

Regards,
Mr. RC-CAM

[Foxy]

Mr RC cam, a quick one for you, how do you find the quality of the gimbals and switches on that unit? I bought an xf421(the next model up from that unit) and had nothing but trouble with it, gimbals binding, then breaking(jr gimbal plastic is great with CA) the programing switches then went intermittent. I always case my TX and its not used near fuel. Maybe i just got a dud. Anyway it made me upgrade to an x388s which I love, the sticks are sooo much nice to use. Have any mods for these units?
Thanks for your time, the Ezone is lucky to have you on board.

Adam

[Mr.RC-CAM]

The gimbals seem fine, but I have not really spent that much time playing with them (I've had the Tx for less than a week). There is only one stock switch (trainer), which is not bad quality from what I can tell.

When the JR XP642 (now retired) was sold a few years ago there was some plastic issues with its gimbals too. I thought that this was limited to the 642, but perhaps it affected the XF421 as well. The problem was that the gimbals would fall apart due to poor plastic quality. I believe the fix involved new gimbals that were similar to the XP652 (which are very nice).

I don't have any mods to offer for the 388, but I'll bet there is something in it that could be hacked. ;)

RC-CAM

[fixwingagain]

I have 1 Quattro and am looking for a good deal on another for use as a buddy box. Since I will have 2 TX I am thinking of giving your hack a try. Never can have too many channels :)

Thanks for posting.

[Vince98]

Mr. RC-CAM,

What steps could be eliminated if I only wanted to add
the 5th channel and SPST switch only to the Quattro?

Any updates on the other mod you were looking at for
the Quattro?

Thank You,

Vince

[Mr.RC-CAM]

What steps could be eliminated if I only wanted to add the 5th channel and SPST switch only to the QuattroMy Tx is all buttoned up, so I cannot confirm the steps or this shortcut mod:

(1) Install the SPST Gear switch at CN5.
(2) Move R6 to location R5.
(3) Do nothing else.

If you try this out please report what you find.

Any updates on the other mod ...I have not had any time to do anything with it. Sorry.

RC-CAM

[Vince98]

Mr. RC-CAM,

There is no mention of resistors R5 and R6 in the
original mod! You only mention moving R7 and R8 in the
original! Are R5 and R6 the correct ones for adding only
the 5th channel?

Thank You,

Vince

[Mr.RC-CAM]

Moving R6 to R5 configures the microcontroller for 5-channel operation. My original mod was for a 6-channel upgrade. That is why it is different.

RC-CAM

[Vince98]

Mr. RC-CAM,

Thanks for the clarification!

Vince

[gouch]

Pretty impressive electronic hackery, rc-cam, but what the heck is a 0 ohm resistor? Doesn't it defeat the purpose of the resistor by having no resistance :confused: Electronics are not my field :)

Cheers
Paul

[Mr.RC-CAM]

...but what the heck is a 0 ohm resistorIt is a jumper wire in the shape of a resistor. It allows machine stuffing of circuit boards (and ensures proper placement even when the human counterpart goes at it).

The are often used on single-sided circuit boards to help jump over traces (poor man's two-sided board). In this case they are used as configuration jumpers and removable MCU input protection grounds.

RC-CAM

[gouch]

There you go! thanks RC

Cheers
Paul

[mac_man]

Mr RC-Cam,

Just out of curiosity, how goes the investigation on the other part of the Tx Hack ? Would be interesting to see what you have found.

:)

[Mr.RC-CAM]

I have not done much about the "secrete" feature. There appears to be support for V-Tail mix. I haven't had much free time to validate the hack. It is low on the list, so it may be a long time before I get back to it (if ever).

RC-CAM

[Marion]

Thanks for ther info. Nice job!
I would like to add a proportional function to the "gear" switch (channel 5) on my Futaba T6xas. Do you knoe if this can be done??
TIA, Marion

[Mr.RC-CAM]

I do not know for sure. My hunch is that it is not possible. Late model 6-ch Futaba Tx's usually use a digital (not analog) input on the gear switch input.

RC-CAM

[daisycutter]

Got a mod for a Focus 4?

[Mr.RC-CAM]

Focus 4 Mods: http://www.rcgroups.com/forums/showthread.php?s=&threadid=55575

RC-CAM

[daisycutter]

Thanks Rc-Cam, just what i needed for the New Year, haha :)

[MegaTesla]

Hi. I did the mod on my Quattro and it works great - except, the channel 5 & 6 servos only have half (90degrees) travel...

Can I fix this? Maybe add a few resistors somewhere...??? Thanx for any help.

-Pieter
Stellenbosch, South Africa

[Mr.RC-CAM]

I recall that both channels give the standard/default JR R/C Sig range (~1.1mS to ~1.9mS).

For sure, there is nothing to adjust on Ch-5. However, Ch-6 should give the same amount of travel as the sticks do. Compare the servo on, say the throttle channel, then decide if the travel is substantially less on CH-6. If it is, then the new pot probably has limited rotational range.

RC-CAM

[hunty]

any update on this mod? I've recently bought the quattro but now wishing i had a 5th or 6th channel for flaps/retracts etc etc.

who has done this mod successfully?

Cheers,

[hunty]

well i threw caution to the wind and did the mod for just the gear switch, which only involved moving the smt resistor from r5 to r6 and bam it works like a charm! highly recommended mod!!

[DragonPhyre]

Also did the CH5 mod without a hitch. Very easy mod, for the extended functionality. (tweezers are your friend for SMD.) Will tackle the CH6 mod later, whence I can find the parts for a reasonable price.

As a side note: What is a good way to test SMD caps for their value? When I worked at my last job, we had a really expensive machine that would test caps to make sure they were within spec... As a side benefit, it was also very handy when one would come in unmarked and you wanted to know the value ofit.

[coloradoz]

Nice hackery - but do you know how to add expo to a xf631?

[AeroFlyer_BR]

Hi guys, I'm nkownning this hobby now and just bought a complet radio JR S400 Pro.
I wanna know if this mod works for it?

Thank!
AeroFlyer
Rio de Janeiro
Brazil

[village_idiot]

This pooped up as current, so I thought I would comment. Nice work. Having had my Quatro apart I thought this might be possible, maybve I'll have to do this and try it out.

[Orion1222]

Im gonna have to give this mod a try just for the 5th channel

[village_idiot]

BTW, if you are careful, you can fit full size components onto the board and it still works just fine. I salvaged everything except the pots and switches. Pots were 10k compact square bodies with quarter inch threaded mounting point. And the switch also needs a quarter inch threaded mounting too. I have not located the reversing switches yet, but haven't really looked too hard either. it would be nice to make channel 5 fully proportional, but I'm not sure if that is possible.

http://img.photobucket.com/albums/v630/vidiot/goodradio1.jpg

My radios have factory installed V tail mixing switches

http://img.photobucket.com/albums/v630/vidiot/goodradio2.jpg

Sorry, no pictures of the circuit board. so you'll just have to take my word that full size components will fit if you are careful.

If you put in a DPDT switch, you could steal power from the circuit board, and put in two leds for the gear channel, one color for gear down ready to land, and one color for gear up do not land. I say this because all I had was DPDT switches and thought about adding some LEDs for the gear, but then decided I would probably just sell my radios when I bought a 9 channel system.

[village_idiot]

I was asked about the full size components, so I took a couple more picture to add to this thread. The components were salvaged from another board and carefully soldered in. No idea if other components need to be changed to make the mixing functions work.

[lekrom]

I did the 6-Ch (Switch and pot) mod. Straight forward, no issues...

[mikere5]

I did the quick and easy mod to add a 5th chanel with a 2 position switch as I need an on/off servo for a camera.

Worked a treat - add the switch and move the 0 ohm resistor from position 6 to 5 - simple and fantastic.

Thanks for the tip!

[The Touch]

Apologies for the thread resurrection. Just tried the mod but it wasn't completely successful. Channel 5 works but six does not. Just checking with the multimeter the Pot is correctly adjusting voltage but the 0ohm resistor on in position R7 doesn't have any power going to it.

I'll keep mucking around with it but I thought someone might be able to help

Any suggestions ?

Thanks

[Mr.RC-CAM]

the 0ohm resistor on in position R7 doesn't have any power going to it.
That is a problem. This is a pull-up resistor (jumper) position, so it should have 5VDC. I suggest you review everything under a 5X magnifier and check out your work.

[The Touch]

only getting ~1.2v on R7 so there is definately a problem. Will keep trying :o Solder work looks ok. Maybe it's my cheap and nasty smd components but I doubt it.

[Mr.RC-CAM]

With the voltage you reported, the resistor is probably open circuit. Your ohmmeter should be able to tell you if the zero ohm resistor is still zero ohms. Excess soldering heat will kill them, so that may have occurred.

[The Touch]

0 ohm resistor still 0 ohms. Replaced the two caps with through hole components, no change. Weird, I must have a bridges somewhere I can't see or something. Ch 5 continues to operate fine.

[Mr.RC-CAM]

One end of R7 connects directly to the 5V supply, which powers the microcontroller. If it was at ~1.2V then the Tx would not work. So, either a PCB trace to R7 is broken, or it's not R7 that you are working on. Double check everything again.