Ron Stahl

My Feedback: (12)

All, today was a very frustrating day for even an experienced modeler and the first time I have ever been upset with JR as a company. First I had a JR791 fail on the bench while rigging my Electra; it's the first servo I have ever had fail in 35 years in the hobby and of course having every servo in my shop but a spare one of these got me worring. Some calls got me a new one after driving 85 miles round trip to the closest hobby shop who had one in stock today; as I am trying to get the plane flown tomorrow before the liberty bell rally. While I was there I decided to make life simple and get two of the new 6 volt DSM2 dual lead batteries from JR with the heavy duty power lead and the std size lead and install my 1221 rx as well since 9 channels made it but just with the elevator servos on a y-harness. I put the new packs on the charger asap once home and replaced the burned out servo and swapped out the 9 ch for the 12 ch RX. Much to my surprize now all of my servos are going nuts on the 6 volt packs with the retract servos really going crazy. A call to my local JR REP Troy Lawicki resulted in us spending 2 hours tracing down that the plane worked fine on 4 cell packs on either rx but now not on 5 cell packs so it was a voltage thing. Turns out the JR 791 servos have a voltage limit and to be able to use them on charged 5 cell packs you need a regulator. No where on the package for the 791 servo or on the JR web site does it give you this info. I did find it you are looking at thier regulators in the info for the 2 output regulator; it tells of the voltage limit that several products like the 791 servo has and this is the cure. So now after 3 wasted hours; my plane works fine with a 4 cell pack and the 921 RX, and I get to spend even more money on a regulator if i want to use my 791 retract servos that are installed in my plane with my 1221 RX since I need one of my $50 5 cell batteries that I have to buy use on my $220 1221rx since you can't use 4 cell packs on them . aint it great!

DavidR

My Feedback: (1)

Ron,

JR makes a regulator for two channels (JRPVR5203) , the 791's are spec'd at 4.8 volts use whatever you want for the packs plug this regulator in between reciever and servos no problems. I use a 1600 mah 2S LiPo with a duralite regulator to the reciever.

http://www.horizonhobby.com/Products...odID=JRPVR5203

Pete737

Hey Ron, I ran into the exact same issue while outfitting my P-47 which used a 6V main battery and the 791's. This was the solution, If you don't mind adding another 4.8 battery. I just used a small 1100 to operate them, They work all day.

Pete

Ehab

My Feedback: (44)

I had a very similar problem with the 791 on my H9 P47 too. As a matter of fact , I had Three conflicting problems...One with the 791 as you described. The second problem, was that the Retract servos, the 791, would cycle on power up and cause the LG to colapse and then try to come down again!!!! I had to go back to 4 cells, but then (third problem) JR requires the DX7 and its 2.4 G systesm to run on 5 Cell!!! Needless to say, I almost lost my P47 till I finally ran two 5 cells thru a power system and, every time BEFORE I powered up the P47 I would ask some one to lift her up a bit to allow thw 791 to fully retract and go back to the down position.....The P47 flies great thu, the DX7 had to go....The solution up there may be your easiest and best choice...good luck.