Hydrocarbon92
Rock Crawler
I finally got around to doing the firmware hack on a freebe GT3B I got a while back. While opened, I decided to also look at changing the linear regulator. The 78M05 was 40% efficient at best, and now it's in the 80-90% range. I also saved $11+ over the "drop-in" switch-mode regulator I've seen elsewhere.
First you need to pull it apart. There are several guides to opening this transmitter, it's basically 4 screws on top and 2 unseen tabs on the long sides. Squeeze the 2 sides of the lower shell under the face and pull on the face gently.
Then I took the $0.60 MP1584 I got direct from China (I actually get them in lots of 5+ for $0.30 or less). De-solder the original reg, or just cut the legs. Solder wires to the MP1584's IN+, OUT+, and either IN- or OUT- (ground is shared). The regulator leg/hole closest to the black screw is IN+, the middle is Ground (IN- or OUT-), and the leg/hole closest to the power button is OUT+. Connect the wires accordingly.
Last you simply secure the regulator, seal the radio back up, and power it on. The voltage monitor works like normal too! At this point you can also switch to lipo/etc batteries - this reg will accept 2S to 7S, although 3S would keep the stock voltage monitor settings happy.
Word of caution: these regs are usually adjustable, and many aren't set to 5.0v. Mine were set to 6.0v, so you should test it out first. There are some other fixed 5v regs, usually with USB ports on them, so you can save yourself some effort with that route.
Here's the large pic if you need detail:
https://i.imgur.com/c9DFQIW.jpg
Here's a link to Aliexpress for this type of regulator, although they're also sold on ebay & other places. They usually contain "lm2596" in the name since that's a very common regulator they replace: https://www.aliexpress.com/item/1PC...-9e03-480b-8e5d-01318473aac7&rmStoreLevelAB=5
BONUS: you now have a cheap source for a 2A cont./3A peak UBEC! I use these on all sorts of projects. The MP2307 is smaller & efficient, but the MP1584 usually offers smoother power output.
First you need to pull it apart. There are several guides to opening this transmitter, it's basically 4 screws on top and 2 unseen tabs on the long sides. Squeeze the 2 sides of the lower shell under the face and pull on the face gently.
Then I took the $0.60 MP1584 I got direct from China (I actually get them in lots of 5+ for $0.30 or less). De-solder the original reg, or just cut the legs. Solder wires to the MP1584's IN+, OUT+, and either IN- or OUT- (ground is shared). The regulator leg/hole closest to the black screw is IN+, the middle is Ground (IN- or OUT-), and the leg/hole closest to the power button is OUT+. Connect the wires accordingly.
Last you simply secure the regulator, seal the radio back up, and power it on. The voltage monitor works like normal too! At this point you can also switch to lipo/etc batteries - this reg will accept 2S to 7S, although 3S would keep the stock voltage monitor settings happy.
Word of caution: these regs are usually adjustable, and many aren't set to 5.0v. Mine were set to 6.0v, so you should test it out first. There are some other fixed 5v regs, usually with USB ports on them, so you can save yourself some effort with that route.
Here's the large pic if you need detail:
https://i.imgur.com/c9DFQIW.jpg
Here's a link to Aliexpress for this type of regulator, although they're also sold on ebay & other places. They usually contain "lm2596" in the name since that's a very common regulator they replace: https://www.aliexpress.com/item/1PC...-9e03-480b-8e5d-01318473aac7&rmStoreLevelAB=5
BONUS: you now have a cheap source for a 2A cont./3A peak UBEC! I use these on all sorts of projects. The MP2307 is smaller & efficient, but the MP1584 usually offers smoother power output.