DE-SW033 Application Note
Improving the runtime of the Spektrum DX6

The purpose of this project is to replace the voltage regulation solution in a Spektrum DX6 transmitter with a more efficient one. In doing so you can more than double the runtime of the transmitter. This is a surprisingly simple project, and anyone with average soldering iron skills can do it.

Tools/parts list:
Soldering iron (15 to 60W will be fine)
Phillips screwdriver (+ head)
Pliers
DE-SW033 voltage regulator

Total project cost: $16

Technical theory on the project:
The Spektrum DX6 runs off a 9.6V NiCd battery pack, which is 11.2V when fully charged. The internal 2.4Ghz circuitry runs off of 3.3V, and is drawing the majority of the power in the transmitter. To get from 11V down to 3.3V, the Spektrum engineers chose to use an LM2937 3.3V linear voltage regulator. Linear voltage regulators are dirt cheap, but are very inefficient when run from high voltages. 11V is more than triple the output voltage of 3.3V, so a lot of power is being wasted. Replacing the linear regulator with a switching DC-DC voltage regulator (DE-SW033) will be a much more efficient solution, so less power will need to be drawn from your battery pack to accomplish the same task. In other words, you will get a significant increase in battery life. Please see A Beginner's Guide to Switching Regulators for more information.

Alright, let's do it!

First unscrew the plastic cover of the transmitter. The screw positions are shown here.


Here is what you will find after you open it up.


Here you see the LM2937 linear regulator that the transmitter is using to power the 2.4Ghz RF section.


You need to desolder this regulator first before replacing it. We recommend desoldering one pin at a time, and bending them upwards as you go. This makes it a lot easier to do. As for removing the main body of the regulator, there will be a small exposed metal tab underneath the large black ceramic body. Heat up the metal tab enough to melt the solder under the body, and this should allow you to pull the remainder of the regulator off the board. Be patient as it will take a long time to heat up!


After desoldering the linear regulator, this is what you will see.


Here is the DE-SW033 that will become the new voltage regulator for the Spektrum transmitter.


Bend the DE-SW033's connector pins forward about 30º as shown here. This will make soldering easier later on.


Solder the DE-SW033 onto the board as shown:


Done! Put all the screws back in and start flying again.


Results:
These results were taken with a fully charged battery pack.
Before modification: Total draw from the battery pack was 280mA , 3.14 Watts. Runtime was measured to be 2 hours 19 minutes.

After modification: Total draw from the battery pack was 123mA, 1.38 Watts . Runtime was measured to be 5 hours 33 minutes.

At 123mA, the DE-SW033 doesn't even get warm so don't worry about heatsinking/airflow.

Further improvements:
For even more run time, you could replace the 9.6V NiCd pack with a greater capacity 3s lithium pack.

Updates:
Some of the gang at RCGroups have some soldering tips here

This mod can also be done with the DX7

***The 5V DE-SW050 is NOT the voltage regulator you want for this mod. You want the 3.3V DE-SW033***

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