Futaba Magnum Jr 3S conversion

[juicedcoupe]

I have six Futaba Magnum Jr's and two Airtronics Xl2p's that use the fragile and nearly impossible to find angled battery holders.

Even if you manage to find one, most currently made AA's are slightly larger than those of the past. Some of the cheap "Heavy Duty" ones fit okay.

Having gotten tired of dealing with that, I went searching for another option. The owner of my local Hobbytown (who I met in the 90's) suggested a small 3S drone battery.

So I brought a transmitter in and we went through his inventory and found one that fit.

I made some pigtails with 20G wire and fed it through the original spring, soldering to the existing wire and tab.

The pigtail is long enough to make/break the connection without having to pull against the wires.

Then slide the battery in and stuff the wires behind it. The fit is snug but not tight. Lightly pulling the wires will get the battery out.

I didn't bother charging the pack but it shows nearly full power with just a storage charge.

[LusBus]

Jus be careful, because this tension can damage RF output transistors over time, especially if the antenna is not perfect. The transistors suffer from overheating. Remember that this RC was designed for 9,6V and a higher tension was only present for a very limited time with dry batteries or 8 fully charged NiCd cells. An easy way to deal with that is to solder one or two diodes in series with the pack. Added value is an reverse polarity protection.

[juicedcoupe]

Jus be careful, because this tension can damage RF output transistors over time, especially if the antenna is not perfect. The transistors suffer from overheating. Remember that this RC was designed for 9,6V and a higher tension was only present for a very limited time with dry batteries or 8 fully charged NiCd cells. An easy way to deal with that is to solder one or two diodes in series with the pack. Added value is an reverse polarity protection.

AA alkaline batteries are rated at 1.5 volts (many test in the 1.7+ area), not 1.2 like nicd and nimh batteries. So it would be a 12V pack, not 9.6. Alkalines are considered dead at 1.35V each.

And per the manual, the device is listed as being 12V.

[GoMachV]

I feel like the voltages are pretty relaxed by the time we got to this radio. Earlier radios had a dummy cell when using alkaline. If it were an issue at this evolution of the radio I suspect they still would have had it