solpete

Hi! My 1 year old futaba 7 is out of range... the servos begin twitching after 10 ft (antenna in) and about 30 ft (antenna out). Help me come with some hints what could be wrong, I have crashed with the receiver once before but it was inside bubble foam protection. How could I check whats wrong and how to fix it ... VERY SAD! I am using 2 servos which are 10 years old but working, havent noticed they be the fault.

thanks!

BuschBarber

My Feedback: (2)

I have had to deal with situations like this for many years, however, since I purchased my Futaba 9C and my JR9303, I have not had any Tx related problems.

Range problems could be Tx, Rx, Batteries, Servo, or RF Interference.

I had been using my Futaba 8AUPS, for a month or so, when I noticed, during a Range Check, that I only had 10 ft of range, before jitters started. I tried a friends RF module in my TX with no difference. I tried my RF module in his TX and got great range. I opened the back of my Tx and found that there was a Crack, in the board, where the Antenna, Battery, and Trainer Cord connect. The Crack was across the Antenna circuit. Once it was repaired, I had no more problems that were Tx related.

When diagnosing Range problems, I like to Route the Antenna out, of the plane (as close to the Rx as possible) and away from Switches, Serovs, Pushrods, and metal to metal contact. If the Range improves, I try to route the Antenna out of the fuselage and out to the Vertical Fin, Stab tip, or Wing tip. Check the Range as someone Rotates the plane at 90 deg intervals.

Disconnect the older servos and try connecting newer ones and just lay them in the fuselage.

Check the Continuity of the Rx Antenna. You can get a Break in the Antenna wire and not the insulation, so you would not realize that the Rx Antenna was shorter. Tighten the Tx Antenna.

Is this a 7CAP and is it on 2.4Ghz or 72Mhz, 50Mhz, etc.?

solpete

Hi! Sorry about the first very short question, I was typing it on my mobile phone.

I have the Futaba T7CP tx together with the standard Futaba R137F receiver that came with the package. I got home today and began testing some, I think it is the LiPo 7.2 Volt -> 6 volt converter that is the issue ... I connected my 4.8 Volt battery pack instead and it showed MUCH less twitching. It still twitches slightly (between my bedroom and living room) but the battery is currently drained (showed red on VoltSpy) and i think the jitter could go away when its fully charged. Now I have to go and read some about these 7.2 -> 6 Volt converters, I read somewhere that people had similar issues.


I am also going to try removing the servos one by one and experimenting with another Receiver to see if those create any problems...

solpete

My problem remains... I did remove the faulty volt converter that was transmitting strange signals... But when doing range check on the field it seems the problem remains. I am not sure now if the converter was faulty, maybe it just enhanced some signal that is faulty from the beginning in the receiver. Now I dont know what is wrong. I have opened both transmitter and receiver and by just looking at the condensators and leads they look fine. I also tried moving the crystals and exposing the systems to slight vibrations - nothing. I will have to go to the store with my radio and change crystals or receiver... very irritating, sometimes I whish I bought a 2.4 Ghz system

solpete

BTW I also measured the resistance using a multi-meter on the receiver antenna and the resistance was withing the right order of magnitude considering the atomic properties, length and diameter of the antenna.

Smacka

It sounds to me like you are being hit with stray RF noise, a killer of the 72 MHz band. You would be miles ahead of your issue by crossing over to the 2.4 GHz band, and much happier.

Just in case your "crash" created/caused some hidden damage to your receiver...if you have another receiver, transfer the crystal and give it a try. Damage is not always easy to see ESPECIALLY since you can never see electricity/electrons. You could have a damaged solder pad that has an intermittent connection.

I know this is not much help. I wish you luck.

Have a great day,
Smacka

solpete

I am using the 35 MHz band , not the 72 MHz. I am going to the store now to check with another receiver

cheers!

and yes your help is good !

Rodney

Unless this measurement was zero (or so close to it you can't tell the difference) it is to high. You should not be able to measure any resistance between the tip of the receiver antenna and the circuit board unless you have a meter that will measure in microohms and has zero lead length on the probes, i.e. this should be a dead short when measureing ohms.