Serious servo jittlers
 

I'm getting some serious jitter of all the servos. I used to experience this when the Rx battery got low on charge and it would disappear when I swapped out the battery. Now I'm getting it even with a freshly charged battery in both the Tx and Rx and it's pretty much constant. Even worse, the Rx doesn't seem to recognize the Tx when it's even a short ways away (more than about 2 feets). From a (very) short distance I still have control but even then there are jitters.

What's going on here?

The model was recently involved in a crash but I don't want to just to conclusions that THAT is the cause of the radio problems. Still I didn't make any changes to the radio set up during the repair.

RE: Serious servo jittlers
 

"The model was recently involved in a crash but I don't want to just to conclusions that THAT is the cause of the radio problems."

I'll jump to that conclusion. If the radio functioned properly (with adequately charged batteries) before the crash, and now doesn't function properly, then it was damaged in the crash. Send the RX and TX off to be checked. Check the switch, too. Check the battery pack, was it damaged (dented or distorted)?

DON'T RISK YOUR PLANE!

Dr.1

RE: Serious servo jittlers
 

Clearly, it can't be flown until I get this problem cleared up. I suppose I can try swapping out different parts of the system until I find a culprit. It does not appear to be a problem with either the Tx or Rx battery. Being in (rural) Japan and not under FCC restrictions I can also try swapping out the TX and RX crystals -- which I've already had to do to use my American purchased Airtronics VG6000 radio in Japan anyway.

If the Rx were damaged in the crash, what's the likely type of damage? Is the crystal the part most delicate part? This wasn't a devistating crash, the only real damage to the fuse was a loosened firewall and the nylon bolts of the wheel bracket being cut through (as was supposed to happen). the wing and tail feathers were all unscathed. The Rx was well protected and wrapped in foam.

RE: Serious servo jittlers
 

You never know what type of damage may be suffered in a crash. If the crystal is cracked, the radio won't function at all. A tuning can may have been knocked out of tune, the PC board may be cracked, there may be a loose solder joint. None of these is easily repairable by an amateur. Send the TX and RX in for repair. The repair shop will need the TX to properly tune the RX. Places like that usually don't charge too much.

Dr.1

RE: Serious servo jittlers
 

OK. Test results are in. When I swapped out the entire RX unit (everything else the same) the problem disappears. Next I swapped out just the crystals (from working set to potentially damaged set) and the problem is there. Thus it isn't the crystal but does appear to be a problem with the Rx unit.

Bummer. I suppose all I can realistically do at this point is bring it with me on my Xmas trip to the southern Cal (just a couple of miles away from the Airtronics headquarters) and see if they can bring it back to life. I suppose I could try to ship it off to Sanwa here in Japan but who knows how long that would take with all the confusion inevitably involved in these sorts of "cross-cultural" encounters.

As far as what specifically is wrong with the Rx, DrI is certainly right: nothing an amateur can fix. But it is curious that I get a certain type of cut-off. The Tx antenna needs to be extended even very close. Makes me wonder if there hasn't been some damage to the Rx antenna.

Guess I can always fly it with the other transmitter until I can get a replacement.

RE: Serious servo jittlers
 

BTW, I should mention that guys here in Japan buy and swap out new crystals all the time. Just what effect does "tuning" have?

RE: Serious servo jittlers
 

you can buy a new reciver and get the one you have fixed in the meantime to use in a second plane.recievers can have crystals dropped in them no problem

RE: Serious servo jittlers
 

In the US, the FCC is concerned with possible "Spurious" signals that the transmitter may produce after swapping crystals. Without testing on a Spectrum Analyzer it is difficult to know EXACTLY what is going on. Obviously the RX can cause no problems but can still be "optimized" by careful tuning.

For the relatively small (compared to the cost of an airplane) cost, it is worth checking to be sure.IMO

Even if you were to fine a problem with your RX, you may not find ALL of them. Let a skilled tech have a look at it and be sure to tell him exactly what happened and what you have observed. Nothing is harder to troubleshoot than: "It just don't work right sometimes".

Good luck.

RE: Serious servo jittlers
 

If your receiver is a dual conversion receiver, there are two crystal in it; the one easily replaced and one soldered in. Yes, these are the most fragile parts of the receiver and most easily damaged. Unfortunately, a cracked crystal can appear to work at times and then quit or be intermittent if there is the slightest shock or vibration.

RE: Serious servo jittlers
 

I don't like to mess around with a potentially bogus receiver. I replaced one earlier this year when I thought I could transfer a receiver from a crashed plane into the new plane. It wasn't working, so rather than try to send it off for repair, I "garbaged canned" it, and bought a new one. Why mess around with a potential problem, the new plane should have the best insurance I can give it. Too many other things to go wrong, like my thumbs.

RE: Serious servo jittlers
 

I'd agree but I'm putting it into a "junk" ugly stik clone ARF that I've crash and patched up several times (with no particular elegance) and that I really just consider a training craft. If I can get 10 more flights out of it and a little learning experience fine. But a new Rx unit here in Japan might easily run me the same as an entire flight pack in the US -- and more than the cost of the model new. I tend to put my best/newest radio gear in my best/newest model and the junkers get "hand-me-downs."

Still it looks like this Rx is probably toast and I'll need to be picking up a replacement somewhere. I certainly wouldn't pay more than $25 to have it repaired.

--Don

RE: Serious servo jittlers
 

Can you pick up a new RX, on the right band, in Cal during your XMAS trip here? That should keep your cost down.

RE: Serious servo jittlers
 

That's the plan. But I don't really care much about which frequency since I've got to pull the crystal as soon as I get back to Japan since they use a different frequency set here. I suppose I could put it in a box for when I eventually get back to the US but who knows when that will be.

BTW, here's the "WWI trainer" I'll be using it in. For the moment I've installed my "best" Rx so I can keep flying. I probably won't get my Flair Legionaire done before the break anyway.

RE: Serious servo jittlers
 

An "Ugly Stik"?

I understand about the crystals. But if you buy a RX for 72MHz band, you can't put a 53 or 27 MHz band crystal in it. That is what I am trying to say. What frequencies do they use in Japan?

RE: Serious servo jittlers
 

This was a little confusing initially as they use the same Frequency (72) but divide the band up differently so that the available set of channels is different that those in use in the US. For example I was flying on channels 27 and 28 in the US but found those were "unacceptable numbers" here in Japan. Here I fly on 17 and 18 (well now only on 18 [:@] ) The channels seem to run up to the low twenties and then there is a big gap until you get to the 50's.

Anyway a Sanwa dual convertion crystal purchased here in Japan (cheap) works fine in an Airtronics Tx/Rx purchased in the US.

BTW, all radios here are set up for mode 1 which seems really awkward to me. I like having both elevator (AOA) and ailerons (bank) available on the same stick. Some the the Japanese guys commented that that my mode 2 Tx is just like a mini joystick on a video game!

RE: Serious servo jittlers
 

Tell them it is just like the control stick of 99% of the fighter aircraft built in the world. To the best of my knowledge, the only (modern) fighter ever built with a control wheel instead of a stick was the P-38 Lightning. One reason was because of the extended mission times that it was designed for.