wings

Hello,

I have a Futaba 7C that I've had for several years. Lately I've only been flying smaller electric planes with hitec electron 6 receivers.

I havn't flown my glow planes for a couple of years due to time contraints.

Anyway, I went to replace the parkzone receiver in a t-28 with one of old Futaba FP-RT27DF receivers and it twitches an carries on like's its possessed when I take two steps away with the antenna down.

Since it still seems to work fine with my hitec eletron 6-receivers I assumed it must just be a bad receiver. So, I robbed a receiver from another old glow plane in the garage and it acted the same way...

Now I'm torn, I'm now afraid to even use it with my electric planes and hitec eltron 6 receivers even though it passes range test and flies fine...

The battery in this TX is pretty old and could probably stand being replaced. But all this is happenening with at least 10.7 volts displaying on the screen.

I'm currently charging the batts in a couple more of my old glow planes to range test them tomorrow.

What to do...

I could spend 40 bucks for a new battery to see if that fixes it. If not, I could send it back to Futaba and have them look at it.

By the time Ido all that I probably will have spent over $100, so it would make more sense to upgrade to 2.4Ghz

Problem is, I don't really have the extra cash for that right now. I've taken great care of this radio and I love it, its perfect for me and it great shape and I really hate to change to 2.4 when all my planes have 72Mhz receivers.

Any suggestions or comments on what to do? Could old battery be culprit even though voltage is fine when this happens?

Thanks,

Matt

redfox435cat

what does the battery read when fully charged, mine is always over 11.

fizzwater2

My Feedback: (61)

you mention the battery voltage on your TX, what was the voltage on the RX battery?

Campgems

Your tx battery will put out enough power down to near 9V, so it is highly unlikely that the TX batteryis your problem. That doesn't mean that it is good for a long afternoon of flying, but for test purposes, it is OK.

Are your antennas on the rxs full length and straight. Are you standing to close to the RX? stand off about 10 ft and see how it goes. Are the Rxs on the same channel as the TX. Proper Xtals for that receiver ??

It depends on how the RX's were stored, if they were exposed to big swings in temps and were in an outside/garage environment with big swings in humidity, they may have cooroded and are no longer good. You could pull the case off and have a close look inside. If you see green stuff growing, it's toast. If it looks clean, that isn't the problem.

Does the 7C allow you to shift between PPM and PCM, and if so, are you in the right mode. How are the RX batteries. Check with an expanded scale, loaded volt meter or a Voltwatch pluged into a spare channer on the RX.

$40 is to much for a TX battery if youi decide to replace yours. Check on Ebay. I've picke up some 2500mah NiHd Tx packs for around $15 each. RX batteries for $10 when you buy four.

Try another TX on the same channel. One of your club members must have one you could borrow for a test. It doesn't have to have all the bell and whistles that the 7C has, just be on the same channel and same mode as your receivers. That should narrow down your problem quickly.

Don

wings

Thanks for the replies guys.

Ihavn't checked the voltage to the RX, but it is fed through the BEC of the ESC. Good suggestion, maybe the BECis not working correct. I will check voltage at receiver. Although the control surfaced seem to move wtih authority when I move the sticks.

I did take the cover off the first receiver, thought maybe the antenna wire was not solder good or something. Everything looked good on the inside.

The TX does allow for switching from PCMto PPM. I've never messed with that setting, but I will definitely give it a check. Ihave a new SU31 electrify that I just put together last weekend. Only flew it 3 times so far.(may be a while before Ifly'er again until Iget thi solved) . Anyway, Iturned it on at the same times as the other plane with the FP-RT27DF. The SU31 with the Hitec receiver behaves just fine, but theT-28 with the FP-RT27DF twitches like crazy.

That's got me baffled.... I guess it's possbile I have two bad FP-RT27DF's, but Ithink that's highly unlikely...


Is it still recommned to send radio's back to Futaba to have them "tuned" periodically? Or is that a thing of the past?

Thanks again for the quick replies,

Matt

bigedmustafa

My Feedback: (2)

The glitching and twitching you're experiencing has two common denomenators: your Futaba 7C and your Parkzone T-28 Trojan.

The Futaba 7C is working fine and passing range checks with other planes.  Perhaps the answer lies within your T-28 Trojan. 

Is the receiver placement far enough away from the brushless motor and speed controller to prevent it from picking up RF noise?  Have you tried different ways of mounting your receivers and is receiver placement affecting the range tests?  Are there any metal-to-metal connections with any of the control surfaces that could be generating RF noise?  What kind of results do you get when you try range checking your old Futaba receivers in other planes besides the T-28?

A problem with your Futaba 7C transmitter wouldn't be selective about which receivers or aircraft it causes problems with.  There are a number of other things to consider before tossing away your trusty 7C radio.

It will take some patience, but keep working through the glitching as best you can and you will eventually identify the source of trouble.

Good luck!

Bax

My Feedback: (11)

Before you go further, you may want to check the operation of the system when you are not using the speed control with BEC.  Disconnect the speed control from the receiver and plug in a regular 4-cell NiCd (or NiMH) battery pack.  Check the operation and range of the system.  Many times, a speed control/BEC will feed back erratic signals to the receiver and cause operating difficulties.  There is no way to know if you have a compatible receiver/speed control combination until you've tried it, or seen it work out.

If you still have problems when you have the receiver and servos operating off a battery pack only (no speed control/BEC), then you may need to send in the transmitter, receiver, or all to the service center to be checked.

wings

Thanks again for the feedback guys.

I think I determined the problem.

I dug out and charged up my old Futaba 6ex radio, and it acted the same way. Thank goodness, didn't want to drop money on a new radio!

I also charged up an old glow plane and did a range test side by side both planes both radios.

The parkzone twitched like crazy both times while the glow engine plane stayed still.

So, I went into the garage and dug up a couple old Hitec servos and plugged them into the t-28 receiver (the futaba, one) and they didn't twitch...

So, vioila, the parkzone servos are not compatible with my futaba receiver...

Here is another mystery. I checked online to confirm my theorey and read in a couple places that the pots for the parkzone servos are located in the parkzone receiver. Makes complete sense right? That's why they were going berzerk...

Here is the strange part. I have been flying my T-28 for weeks now with a Hitec eletron 6 receiver and parkzone servos with no incident. How in the world did the servos function correctly with no pots?!

I only recently put the futaba receiver in the t-28 because I robbed the Hitec from it for my new su31. I figured the extra weight of the futaba receiver wouldn't make much a difference in the T-28...


Anyone have any ideas how Imanaged to fly the T-28 with parkzone servos (supposedly without pots) for nearly 2 months with my hitec receiver???

Mystery almost solved, but not quite...

Campgems

That can't be right.The pot is mechanicaly attached to the output shaft of the servo. That is how the servo determines it has moved and adjust the internal pulse width to to compair to the RX pulse width to determine which way to move, how far to move, and when you are done moving. SO, unless there is a mechanical linkage from the output of the servo to the receiver, the pots just can't be there. There has to be another explaniation to your problem. Receiver to servo compatability could be a problem It is worth looking into. but the pots are in the servo, Receiver signal output ampatitude is an issue with one of the Futaba 2.4ghz receivers, but only on some servos and some special applications, IEsmoke pumps. I've not heard of an issue with the 72mhz receivers.

What is more likely is that Park zone servos ANDthe HiTech eletron 6 are a different shift than the Futaba receiver. If that is the case, then what is happening is that the futaba servos are expecting a pulse between say 1 and 2 ms long, with say a positive pulse. The hitech receiver is putting out a negitive pulse and what the servo is seeing as a signal is the long pulse between signal pulses. That would drive the to destruction if left to chatter around. The plus and negitive pulses and their width may differ from my example in regards to Futaba or the

Check the details on both the park zone servos and the hitech receiver.

Don

wings

Campgems,

You're right. That doesn't make sense. I think what they meant was the servos didn't have the electronic components to read the feedback from the pot to tell the servo where to go. The servos they were speaking of supposedly had 5 wires, and my ParkZone servos have three. So must be a completely different issue.

It's definetly a compatibility problem of some sort. I can't find much info on the parkzone receiver, but the futaba one and hitec both are negative shift.

Since the parkzone servos worked perfectly fine with the hitec negative shift receiver, then I would think the parkzone receiver would have to be negative shift also right?

I'm now confident the tx is not the problem, so at least Igot to fly tonght! After range checking about a zillion times just to convince myself that it was OK, lol I went as far so to measure the distance I walked away with a tape measure to be 10000% it was well over 100ft. paranoid? I think so, lol.

But I am still anxious to find out why the parkzone servos work with the hitec negative shift receiver but not with the futaba negative shift reciever.

Campgems

Some of the Hiteck receivers are dual shift. If your's was one of them, that that would explain the problem It woud work with either the Parkzone, or futaba receivers, but the parkzone would only work with the Hiteck. You may want to check that out.

Don

wings

I just checked, the hitec is marked negative shift...

But thanks for the suggestion...

MaxTakeoff

I realize this is an old thread but just in case someone else finds it useful like me ...
There are two types of Parkzone servos, ones with 5 wires with the pots in the rx and regular ones with 3 wires. I think you got confused wings, when you found the incompatibility threads. So that explains why the regular 3 wire Parkzone servos work fine with your hitec rx.
I found this thread because I'm having some weird glitching with my 7C and various rxs. It doesn't seem to be range related so I was concerned that my tx was faulty but now I'm thinking that it might be my Parkzone servos having some sort of issue with my rx - I hope that's what it is.

wings

It is still a mystery to me why those Parkzone servos didn't work with my 7C. Just one of those things I guess, lol...

Leadsolo

Hi Wings, i realize it's a year and 2 months since Ur post but .... anyw, i hv a Hitec Electron 6 (Dual Conversion) 35Rx and am wondering ... where are the markings for Positive or Negative shifts shown on the Rx unit ? I can't find 'em on any surface of the Rx []

I use a JR Tx and the glitches are horrible - The funny thing is, all was cool at first and this seems to be starting after 25 flights or so (different fields / locations though) ... hmmmmmm [X(]

I'm just worried I'm using a Negative shift Rx with my Positve shift JR Tx - Also I notice the servo slots on the Rx are for Futaba Servos ....

Pls help ... Thanks !![&o]

fizzwater2

My Feedback: (61)

it wasn't the 7C and the parkzone servos. You stated that you tried your 6ch TX and got the same results. It's the combo of the Futaba RX and the servos. Did you try Bax's suggestion of eliminating the ESC and using a battery directly into the Futaba RX with the parkzone servos? It could be the incompatibility lies in the ESC/RX, not the RX/Servos.