[Cougar429]

Len, he already mentioned in the OP he had tried multiple receivers with the same issue.

Yes, you can cause problems if there is a direct metal/metal contact between the engine throttle arm and servo, which is why I always use a plastic link at the throttle end on all my setups. 72MHz is really vulnerable to loose mufflers and other contacts like that, but I'm assuming the saturation problem is also with the engine off.

If you can cure the problem by unplugging the wing servos there are a few other things I would try if this was mine. First would be to see what the voltage is at those wing servos when moving. Long extensions of small conductor and higher connector count can all lead to power and signal loss at the end. Also, without knowing your power setup the next may not help.

Plug some servos directly into those channels and see if the problem persists. If not then replacing the extensions with ones of larger conductor may be one solution.

The reason I ask about power system is NiMH may not put out enough to supply a high servo count or digital servos, (I have seen some pull up to 1.6A each and the specs on ones I checked earlier this week showed 3A!). Same with switches and extensions. When you up the number or lead length things can start to add up to problems. Most standard servo leads and extensions can be as small as 25Ga, so resistance and voltage drop can multiply. So far I have been making my own with 22Ga wire with no problems.

[stegl]

wasn't quite sure on the number and brand of cells and how old they were. as you say Gary, could be a low voltage issue when under load.

[Crash alot]

Yes I have heard that the newer digital servo's draw far more power and the smaller wiring in the switch and battery pack leave some concern for sure. I was wondering if it was drawing too much load and "starving" the receiver for power?
I installed 2 servo extensions this evening wrapped around a filter from an old computer system onto the flap and aileron channels on the receiver. Put the plane back together and ran it in the garage doorway. With the "filter" installed I cannot get it to twitch but when I pulled the extensions the problem came back. I will have to take it to the field and tie it down to try it again, but I am not sure I trust it?
And sorry I am not sure if I mentioned that it happens only when the motor is idling..

[Crash alot]

Nope that did not work. I flew the plane about 10 or so flights and didn't notice until I reviewed the video from on board (got lucky). Looks like the camera has a shaky problem. Glitches about the same places every time I fly through a certain area..When I tried it this evening in the shop it was as bad as ever??..
Back to the drawing board! I think I need to try a PCM receiver to see if it can wash out the glitches.

[OLD PRAIRIE RED NECK]

Sounds to me like a vibration related issue as is only at idle. 4 strokes do tend to shake more at idle and I would be triple checking for prop balance and metal to metal contact anywhere on the plane including landing gear and especially your aileron/flap linkage. Don't forget the wing strut connections too.

[Cougar429]

Man, I hate when I finish typing a long post and dump it completely for something silly. I went to look at your avatar to see if that is the Super Stearman or WACO.

This is what I call a "Homer". DOH!!!!

With the "filter" installed I cannot get it to twitch but when I pulled the extensions the problem came back

.

James, a bit confused by that one. Do you mean physically tugging on the extensions creates a problem? If so what end?

If the servo end check that the servo mount screws or plate fasteners are not long enough to protrude the servo leads may be rubbing and shorting under tension.

If on the other end check for loose connectors, bad crimps or simply worn female pins.


Also, any system that has been stored long-term with the battery connected can suffer "Black Wire Disease" where the negative side will suffer corrosion in the conductors, switch internals and any pins or ends. Most will be hidden and only evident if you dismantle or peel back the insulation. It's an insidious problem and the reason I discard old power components on any suspect aircraft I purchase. Not worth the minimal investment or time to do a good inspection, (this is also one of the reasons I take so bloody long to get from table to field!).

James, switching to PCM may seem a good idea, but by their nature you may simply be masking a problem. They ignore bad signal frames, either from your TX or interference generated within the flight system. If you have an intermittent problem at this point the receiver may ride through and each discreet bad frame will stay in the last "Good" position. However, if the problem grows more serious and lasts long enough for the receiver to go into failsafe you may lose permanent control.

[kip51035]

A couple of more things. Broken wire: Hold each plug in one hand and pull gently on each wire, if the wire stretches you have a broken wire. Antenna routing: Get the antenna outside the fuselage in the shortest distance as possible. Do not run it past the servos or power switch. Digital servos are always moving and cause a pulsating magnetic field.

[Crash alot]

Gary/ Mervin. I have a lot of metal to metal in this plane. And I have never had a plane with a wing tube either.
I am going to balance and install a wooden prop instead to see if vibration or static electricty is being generated by the prop/washer and plastic cone (grasping at straws)
Gary last night I had the receiver bay open and I was pulling at the wires and fondling the rx. When I was holding the receiver, with the tx under the right wing (I can find a sweet spot) the rx completely loses contact and goes nuts.
Even if I unplug both the flap and aileron at the fuse the right wing is still very sensitive. Antenna in. If I pull the antenna out it reacts differently.
I will have to go over i all again and see if I can find something.
Gary most of the equipment that I have in it now has been poached from other planes that I was flying but I will go through the wires again.
I think this plane is cursed or something. Maybe a priest could help..Lol

[Crash alot]

Thanks Kip I am going to go through them again. It sure seems like excessive interference from something.

Originally Posted by kip51035

A couple of more things. Broken wire: Hold each plug in one hand and pull gently on each wire, if the wire stretches you have a broken wire. Antenna routing: Get the antenna outside the fuselage in the shortest distance as possible. Do not run it past the servos or power switch. Digital servos are always moving and cause a pulsating magnetic field.

[Crash alot]

I am using new 5 cell 2300 ma AA pack. Will that be too small for this? I have 4 digital servo's in the wings (3151) and 1 on the elevator (9451). Analogue on the rudder and throttle (both 3004). (all Futaba)

Originally Posted by stegl

wasn't quite sure on the number and brand of cells and how old they were. as you say Gary, could be a low voltage issue when under load.