Tutorial: AR6100/6300 1S Buck-Boost Mod

[Jeff_Barrett]

DISCLAIMER:
If you do not have the proper tools, experience or skills, please do not attempt this. You will only destroy your RX and have no one to blame but yourself. Helifreak, the author, and contributors are not responsible should you attempt this.

Credit:
"TheSteve" pioneered this modification. All I have done is consolidated information into one cohesive tutorial and filled in the blanks. If you don't have the skills, you can PM "TheSteve" either on Helifreak.com or RCG to get your AR6100 / AR6300 modified.

Purpose (What does it do?):
Many of us want to "Spektrumize" our 4G6 / Novus 125CP for use with our DX6i, DX7, and for those of us lucky enough, a DX8. Because Spektrum RX's are normally rated for 2S operation, they will have a tendency to 'brown out' when the battery drops below a certain voltage. To solve this, we need to purchase a voltage booster such as LVBoost or apply a modifcation to the actual RX itself.

I can buy LVBoost, what makes this mod an advantage?:
Simply put, weight. Our little helis can use whatever break we can give them. Less weight is better. An LVBoost stripped is approximately 1 gram of weight .. this does not include the added weight for wires and connectors. The weight of the regulator chip is 0.1 grams of weight, and when considering that it is replacing an existing chip, it practically adds no weight.

What kind of tools do I need?:
If I have to tell you this, you probably shouldn't be attempting this modification. Almost all items are available at your local electronics supply store (and I don't mean Radio Shack).


That said, here are a list of items required:

• A good variable temp soldering station
• A very fine soldering tip (eg; ST7)
• A good hands-free magnifier
• A project holder (mechanical hands)
• Solder Sucker
• Solder Braid Wick
• Rosin Flux
• Silver Solder (.81mm or smaller)
• 1uF Ceramic Surface Mount Capacitor (Flyback)
• 10uF Ceramic Surface Mount Capacitor (V-Out)
• MCP1253-33X50 Buck-Boost Regulator (Charge Pump)
• Spektrum AR6300 (also applies to AR6100)
• A lot of patience, courage, and a set of standy hands!!!

Total Cost of Parts (2 capacitors and MCP-1253 regulator): = Less than $5 Canadian!!

I normally enjoy a 'beverage' in the man-cave, but I urge you not to while doing this modifcation. You will need ALL of your wits about you.

[Jeff_Barrett]

If I haven't scared you away yet .... then let's quickly look at what it is we're taking out, what we are moving, and what we are adding.

In the posts ahead, we are going to move the big yellow capacitor from it's current location, above the regulator, to the bottom of the RX and put it in parallel with the existing one there. Make sure you keep the polarities the same.

Don't mind the sockets for the servos .... I bought this RX second hand and someone butchered them. I'm going to remove them eventually to lose even more weight.



We are removing a KB31 fixed voltage regulator that normally puts out approximately 3.1 volts. It comes in a 5-pin package (as seen on the RX). Below is the pinout configuration for it:



We are replacing it with an MCP1253-33X50 buck-boost adjustable voltage regulator. As seen below, it comes in a very different 8-pin configuration. We're only going to use 6 of the 8 pins. It's also going to take a little trickery to make all the right connections because of the different package - but it will be well worth it in the end.



If you're still with me, then I'm going to suggest you look at your walkera connectors quickly. They are wired differently than JR/Spektrum and require a quick modifcation. The black and red wires must be switched in the connector.

In otherwords, the BLACK (V-) should be between the WHITE (Signal) and RED (V+) wires in the connector.

[Jeff_Barrett]

MODIFYING THE RX

Let's tackle the easy stuff first.

Using your solder wicking braid and a hot soldering iron, let's remove the capacitor first. You may need to dab a little flux on the existing solder to get it to heat up properly and release. Clean the pads that the component sat on with the wire braid.

Be sure not to damage the component or the circuit board as we'll need them for the steps to follow.

Next, we'll heat up the solder on the capacitor on the other edge of the board and gently nudge one end up a little to make room for the relocation of the existing one. Repeat for the other side. Next, you will need to solder the capacitor that you removed earlier in parallel with the one we just repositioned.

Check your solder joints and reflow them if needed.

Refer to the photo below.

[Jeff_Barrett]

Remove the Linear Regulator

This next part will require a little more finesse and patience. We are going to remove the existing linear regulator. I have been starting with the two upper ones (pins 4 and 5) first and then the remaining ones.

Get your iron nice and hot and apply a little flux to the joints. Wick up as much solder as possible off all the pins with your braided solder-wick and solder sucker. This will make your job easier in remove this regulator from the board.

Once you've gotten as much solder as you think you can wicked up, apply heat to "Pin-5" and gently pry up a little with a pair of tweezers. Repeat for "Pin-4". Go back and forth like this until both pins are free of the contact pads. If you accidentally rip the pad (trace) for "Pin-4" off the board, not a big deal. It's just a bypass and unused.

Gently lift the regulator so that it sits with Pins 4 and 5 up off the board and so you can slide the tweezers under the chip.

Apply heat (and flux) to the remaining pins and gently lift with the tweezers. I said gently!! If you apply too much force or heat, you will damage the traces and / or contact pads. We need these ones!!!

(Alternatively - if you have a really good pair of tiny cutters, you can try to snip the pins, remove the package, then desolder the pins from the board. I suggest that if you use this method, you also use caution not to gouge the board and the traces --- Credit: dbennetya)

Congratulations! The regulator should now be off the board and you should be left with something that resembles the photo below.

Note the pinout configurations and where the traces lead for some of them. This will help us place the new regulator for soldering to the existing pads.

[Jeff_Barrett]

Preparing the new regulator:

There are a few things we can do to help make micro-surgery go a little easier.

Firstly, don't drink a lot of coffee or booze before hand. You'll need all the alcohol for when you're done ... either because you're crying over a wrecked RX or because you're celebrating that you've gotten right!

Let's look at the configuration of this chip and how it's all going to connect....


First things first ... on the top of the chip, there should be a very faint indent in the shape of a circle. This indicates where "Pin 1" is located and helps with orientation.

Remove the pins we don't need:

We won't be using Pin-1 or Pin-7. Take a set of fine tipped tweezers and just snap them off. Careful not to accidentally remove or damage any of the other pins. We actually need those!!

Installing the 1uF Flyback Capacitor:

I suggest that we gently tilt Pin-5 and Pin-6 up just slightly so that they will not be able to touch the circuit board or pads. Next, we want to spread those two pins out from one another slightly. Take an exacto knife and put the blade between Pin-5 and Pin-6 and gently rock it side-to-side and spread the pins. Be GENTLE ... we only need to spread them enough that they will touch the contacts on the surface mounted capacitor.

I suggest having your project holder clamp the regulator so that it's not moving around on you.

Apply a tiny amount of flux to the pins and contacts on the capacitor. This will help the surface mount ceramic capacitor to stick to those tiny pins.

This can be very frustrating, so use patience and a set of small tweezers to gently position the capacitor contacts on top of the two pins. Make sure you have the polarity correct!!!! Positive to Pin-6 and Negative to Pin-5.

Solder that sucker on there and check your solder joints!!!



Placing the new MCP1253-33X50 Regulator:

First thing we're going to do is bend Pin-3 upwards, this will help prevent bridging while trying to solder. We are also going to spread Pin-4 and Pin-2 away from Pin-3.

Make sure the chip will lay flat on a flat surface. Also check to make sure that only Pin-2, Pin-4, and Pin-8 are making contact with a surface. I suggest using a small mirror as a surface to check this.



Next, place the chip on the RX by lining up Pin-8 with the lower right contact pad. (See the photo below for orientation). Pin-4 should be barely touching the top left capacitor pad, and Pin-2 touching the top right capacitor pad. (See photo below). Solder those 3 contact points.

Place the 10uF output capacitor so that one end is sitting on the contact pad, and the other touching the capacitor sitting directly right of the new regulator. (See the photo below). Solder both sides and make sure you have a good contact point.

Get a small set of good side cutters and clip a tiny bit of wire from the antenna to just large enough to reach from Pin-8 to Pin-3. Bend one end of it just slightly and place that end on Pin-8. Place the other end on top of Pin-3, which should be sticking up about the top surface of the chip only barely. Solder both joints.

Guess what? You're done!

Plug it in and test it.... no smoke? It binds? Servos work? Congratulations!!

Go grab a beer you uber-geek!!!

[Jeff_Barrett]

Thank-you everyone for your patience.

I know some of you wanted to post badly ... well ... the thread is now open for discussion.

Thanks again, goes out to TheSteve for this mod and his patience in answering my questions!

Again, if any of you are unable to perform this mod yourself, please don't hesitate to PM "TheSteve" (either here on HF or on RCG under the same name) who will do it for you!

[Jeff_Barrett]

..

[TheSteve]

Nicely done tutorial.

I will offer a few tips that have made it easier for me to perform the mod.

-Always always always use a clean soldering iron!

-More heat is not always better. I typically set my iron to 700 degrees for this operation

-To remove the factory regulator I actually add a little solder to both sides so that the 2 pins on one side are bridged and the 3 pins on the other side are bridged. I then heat one side up and then the other quite quickly which allows the regulator can be gently pushed/flicked off the PCB. You have to be quick but done correctly its very tough to rip a trace off the pcb.
I then remove all excess solder with solder-wick and then clean with alcohol and a cotton swap.

-The flyback capacitor on pins 5 and 6 could touch other contacts on the PCB - this would be bad of course. To ensure this can never happen I use a very small piece of Kapton tape which sticks extremely well to the cleaned PCB and is burn proof. Its tape that all modelers should have, especially if you do any work with LiPo's. Should a crash(or big fingers) ever push that cap into the PCB there is no chance of a smoke show.

-I never add any flux as I find it makes a mess, I do use a very high quality multicore solder that is very fine which makes this job much easier.

-When done clean the area very carefully with a cotton swap and let dry before testing.

[Ampdraw]

Super nice tutorial CC. Well done, very admirable effort.
I'm sure this thread will have soooo many hits in due time.

...and TheSteve great you were nice enough to help when required....but from what I have read (like the whole thread a few times) in the 4#3 brushless rcg thread that is your character. I ran a converter in my 4#3B 2406 rx and it did surperbly....so thanks for all you've brought to this hobby.

Amp

[Jeff_Barrett]

Just a reminder, if you can't do the mod yourself, please feel free to send " TheSteve " a PM and he can do it for you.

[Arcnsparks]

Ever take a look at one of the "OrangeRx" spektrum receivers from HobbyKing?

http://www.hobbyking.com/hobbyking/s...dProduct=11965

Any chance this mod would work on those as well, or is it even necessary? It says input voltage can be down to 3.7 is that worse or better than the AR's? I can post high res pics of the rx if you havent seen 'em out of the case. I would much rather attempt my mod on a couple of these $8 rx's instead of the $50 AR6xxx's!

[Jeff_Barrett]

With the mod, it will allow voltage drops to 1.8v before the RX will brown out. Input voltage is 4-6v on an AR. Even though you're not discharging your battery down to that level, the voltage can drop temporarily under heavy load causing the brownouts.

You will brown out under load with the OrangeRX.

I'd need to have a closeup view of the circuit board to see if the mod could be applied. Might need to tweak it depending on the layout.

You can find AR6300 for $20-30 if you watch the forums carefully.

[Arcnsparks]

Here's some pics hopefully this helps!

[Jeff_Barrett]

The voltage regulator is a variant of this: http://www.datasheetcatalog.org/data...ts/tps7233.pdf

Might be a little more difficult to do because you have less options for mounting the new chip. As you've noticed, it's quite different from the Spektrum RXs in layout.

[aracer]

Originally Posted by Crazy_Canuck

The voltage regulator is a variant of this: http://www.datasheetcatalog.org/data...ts/tps7233.pdf

Since that comes in an 8 pin package, no it's not. More likely
http://www.holtek.com/pdf/consumer/72xxv120.pdf

[Jeff_Barrett]

Ah, much better thanks ... regardless, anything can be done, but difficulty level goes up.

[Discount_Bob]

I'm currently stuck with a non-2801 tx, and it's killing me but I don't wanna pay for a 2801 yet. I PM'ed TheSteve a week or so ago, but haven't heard back (I'm okay at soldering but scared as all getout to do something like this). So, two questions:

First, is this mod necessary if I were to switch to a 2s setup? It'd be alright by me if I "had" to upgrade my motor/ESC.

Second, if it's necessary either way, is there anyone else able and willing to do this mod for others? I'd be willing to pay for your time.

[Jeff_Barrett]

Originally Posted by Discount_Bob

I'm currently stuck with a non-2801 tx, and it's killing me but I don't wanna pay for a 2801 yet. I PM'ed TheSteve a week or so ago, but haven't heard back (I'm okay at soldering but scared as all getout to do something like this). So, two questions:

First, is this mod necessary if I were to switch to a 2s setup? It'd be alright by me if I "had" to upgrade my motor/ESC.

Second, if it's necessary either way, is there anyone else able and willing to do this mod for others? I'd be willing to pay for your time.

A 2S setup makes this mod unecessary. The idea of this mod is to prevent the RX from browning out when uses 1S voltages.

If you want the mod done, try sending TheSteve a PM over at RCG. He tends to frequent there more often.

[Discount_Bob]

That sounds great. I'm having problems figuring out how the spektrum rx then connects to the 2810s, and all I could find were threads talking about how it couldn't be done! Any mods required there? I just wanna get all my ducks in a row before I make the leap. I'm really wanting to use my spektrum tx rather than dump cash into a 2801 for just one heli.

[Jeff_Barrett]

Originally Posted by Discount_Bob

That sounds great. I'm having problems figuring out how the spektrum rx then connects to the 2810s, and all I could find were threads talking about how it couldn't be done! Any mods required there? I just wanna get all my ducks in a row before I make the leap. I'm really wanting to use my spektrum tx rather than dump cash into a 2801 for just one heli.

I'll start a new thread in the main part of the 4G6 forum and discuss with you there...