Crystals Failure?
 

Plane Big Stik 60.... 2 pervious flights, same crystals.... Yesterday after pre-flight cheked O.K. I taxied onto the runway and gave her full power for take-off "Nothing" the elevator would not lift her off, tried to shut-down the power and again "Nothing" and into the wire fence around our field. 80% destroyed..... Later my buddy, 30+ year flyer, checked the plane out. We found that with my original crystals nothing would work, we then changed to another frequency "Crystals" in the radio and receiver and the servos, etc, would work. Back to my original crystals and again "Nothing".

We believe that the receiver crystal failed!

Any idea's, suggestions, or does anyone think our "Autopsy" was correct??

Thanks [&o]

RE: Crystals Failure?
 

Only way to be 100% sure is to replace only the RX crystal. I have had one in flight RX crystal failure. Airframe was destroyed.

RE: Crystals Failure?
 

It sounds like you may have indeed had a crystal failure.

However, your changing the crystal in the transmitter was illegal. Transmitter crystals can only be changed by a licensed shop that can adjust the power output of the radio. Even changing out a crystal on the same channel must be done by a shop as crystals can vary even when they are on the same channel.

If you are interested in the full text of the regulations concerning this matter they can be found at:

[link=http://www.access.gpo.gov/nara/cfr/waisidx_04/47cfr95_04.html]FCC Title 47, Part 95 - Personal Radio Services[/link]

Copied from Futaba's website

Copied from FCC regulations concerning this issue

RE: Crystals Failure?
 

It is a rare failure, mostly associated to exposition of electronics to vibrations or extreme heat.
I would check the working conditions of the receiver in that regard.

I believe the legal issue only applies to the transmitters.

I would recommend replacing the receiver crystal first, then, if there is no communication, just send the transmitter and receiver to an authorized service shop.

Regards!

RE: Crystals Failure?
 

Yes, I did say transmitter crystals in my answer. I posted this because the orginal post stated that he removed BOTH crystals, receiver and transmitter. Since he said he changed to another frequency and it worked I wanted to point out the law in this matter.

Ken

RE: Crystals Failure?
 

Yes, Ken, you are right.

And it is a very important issue ignored or overlooked by many pilots, even experienced ones.

Regards!

RE: Crystals Failure?
 

I have no problem with him swapping the TX crystal for a BRIEF test like he did as long as he made sure no other pilots were flying at the time. Improper crystals CAN (but not always) do strange things in the way of spurious signals. Swapping in a friends RX crystal and seeing if the friends TX could control the plane would be a valid test. (TX must be a compatible type of course).

RE: Crystals Failure?
 

Sorry! I guess I did-not explain myself correctly........ I took another crystal from another plane, same channel, and it indeed worked in the Stik!

Thanks guys[:o]

RE: Crystals Failure?
 

Sorry to hear about your Big Stik.[:@] Just out of curiosity, had that receiver been through a crash before? I put a crashed receiver in another plane and everything was fine until the first time I started the engine. I ran it up to full throttle and then.... nothing. The engine is screaming and I have no way to shut down. Fortunately the plane was restrained and I pinched the fuel line to kill the engine. Sure enough, a new receiver crystal solved the problem but I always wonder what might have happened if that crystal had held in there for a few more minutes. Probably nothing good.:(

RE: Crystals Failure?
 

Had this happen to me too,,had a Goldberg tiger 400 park flyer with a norvel .074 in it and it did a figure 9 all by itself..totally destroyed, had a cheap great planes rx in it....Rog

RE: Crystals Failure?
 

Can you try the "suspect" crystal in a different receiver?

RE: Crystals Failure?
 

This is outdated as the license is no longer required, unless recently re-established.

Yet the FCC has been certifying them with the crystal easily accessable from the front, therefore changing them also legal?

RE: Crystals Failure?
 

Even with the crystal being easily accessible from the front, the change must be done by a shop that can re-tune the radio. These radios are sold worldwide and they aren't going to redesign their cases to sell just of the US. The requirements to have the crystal changed by a shop is still applicable.

Ken

RE: Crystals Failure?
 

The most common cause of a crystal failure is mechanical shock. Remember that there are two or more crystals in each receiver although only one is easily replaceable (the other is permanently soldered into the circuit). Either can be damaged in a hard landing or crash as they are just a piece of quartz ground to size and suspended between two post or wires inside the metal can they are usually enclosed in. The crystal can fracture or one of the leads can be cracked and open up under vibration (engine running). If replacing the plug in crystal does not fix the problem, you could still have a broken crystal (the other one) causing your problem.

RE: Crystals Failure?
 

Should I assume that you are referring to the old "CB" type license that used to be required to operate an R/C TX? Yes, that is no longer needed. As for maintaining them it still requires a license. It requires a Comercial Radio Telephone License or working in a shop under the auspices of a holder of said license.

As for the front mounted or easy access crystals (not modules) these are because these same units are sold world-wide where the same regulations do not apply. Nor are the radio bands as jammed with people all trying to use the same space. Modules are a totally different subject and have different rules that allow their swapping as long as certain conditions are met.

RE: Crystals Failure?
 

Even a brief test is a no-no!!!!

I was flying a new 50cc plane on a specific channel. It's third flight.

While flying low over the field I experienced a glitch, the engine cut out and the plane augured in HARD.

I went to talk to another person there who had co-incidentally turned his radio on at this time. He was NOT on my channel....

A few months went by...

This time I was flying a smaller EP aircraft.... same channel as before... same guy at the field...

I noticed that whenever it passed in front of his location while he was flying my plane would glitch....

I went over to talk to him

It turns out he had changed his TX crystal.

I pulled out my new frequency checker which dynamically displays over/undertones, interference, etc....

Sure enough, his TX was producing an overtone signal smack in the middle of the channel that I was using ( ch 45 ).

This is because he swapped the crystals and in so doing "detuned" his TX.

I told him he owes me at the least a new airframe, but he refuses to own up.

Fortunately he also doesn't show up anymore as well.

RE: Crystals Failure?
 

I did say "as long as he made sure no other pilots were flying at the time". Perhaps you missed that point. It is indeed an important one.

RE: Crystals Failure?
 

Yes it is!

RE: Crystals Failure?
 

One thing that I don't think was mentioned above (I might be wrong): There is no 100% sure way of knowing if a bad Rx crystal caused the crash. Although you can determine that the Rx crystal is NOW bad by swapping out another one on the same freq., it is possible it is NOW bad because you just ran the plane into a fence and damaged the crystal, not because it was bad before it crashed.

RE: Crystals Failure?
 

Of course they would, they already have to make frequency changes and possibly other changes. The FCC just doesn't see this as very necessary. Their concern is to interferance to other bands, not if our planes crash.

RE: Crystals Failure?
 

No, there is no FCC licience to repair RC radios. There is nothing in the regs that require a licence, only Futaba and other demanding it is so. If you go back and reread the reg it says you cannot MODIFY the radio, it does not say you cannot service it. However it says NO ONE may modify the radio and that messing with the frequency so that it transmits on a non RC frequency is a modification. Therefore if you change the crystal you may be modifying the radio. Only someone with the proper frequency analyser and skill can do this and be sure he is not modifying the radio.

RE: Crystals Failure?
 

Re-read post #3 above. You are absolutely in error.

"E). The internal repairs or internal adjustments should be performed by or under the immediate supervision and responsibility of a person certified as technically qualified to perform transmitter maintenance and repair duties in the private land mobile services and fixed services by an organization or committee representative of users in those services.

This mean a LICENSE.

Changing the crystal IS an adjustment which may cause a need for FURTHER adjustments. It certainly causes a need for further testing to determine the status of operation.

RE: Crystals Failure?
 

Not only that but changing a crystal without retuning the associated chokes, can cause serious sideband and overtone issues.

I've the recipient a radio hits caused by an idiot who elected to change his crystal, destroying my plane!

The guy erroneously assumed that he could merely swap out crystals...

I had a plane on a different frequency which had always been rock solid reliable.

I was making circuits of the airfield, and noticed a glitch as my plane went by his station.

I didn't think of it at the time... on the next pass my plane went in when it went by his station...

After the crash I pulled out a frequency checker I picked up that has an LCD display that shows overtones and spikes...

Sure enough his TX was producing a spike on my channel.

When the guy put his original crystal back in, the spikes disappeared on other channels.

I told him he owed me a new plane...

He never returned, never offered to pay, and is no longer a club member.... good riddance!

RE: Crystals Failure?
 

Sport Pilot is so wrong on his statement that no license is required. He either can not read or has neglected to get a copy of the FCC rules.

RE: Crystals Failure?
 

If there was a requirement for an FCC license then it would have said so. Instead it says <b>certified</b>. Read the parts about broadcast, aviation and others were a license is required. I think they have been using factory certification, not FCC license.

RE: Crystals Failure?
 

Here is what the part for private land mobile services of the FCC says about repair of same.

So there is no such FCC license for this, certified means jus that, certified by someone, it is not the same as an FCC license.

RE: Crystals Failure?
 

It is illegal for the consumer/ user to change the TX crystal.

Sport, please do not lead others astray on this issue. I realize you are reading the regs and trying to draw conclusions, but you are off base here. You cannot change the TX xtal, even if it is accessible from the outside of the radio. You do need to be certified/qualified to perform the xtal change. If you want to change freqs on the TX, get a synth based radio or a radio that uses modules. You can swap user accessible FCC certified modules without an issue.

There are good reasons for this restriction. As opjose mentioned with his misfortune, all may seem to work fine with your stuff after you changed the TX xtal, but you might be throwing out RF crap on other channels. If someone broke federal regulations, and by that act, caused me to lose my property, and is unwilling to make things right, I would probably file a lawsuit if the loss was substantial.

OP, as others have said, yes, a xtal can go bad. As others have posted, try replacing the RX xtal, and if the RX still doesn’t work, send both the RX and TX in for service.

RE: Crystals Failure?
 

I never said otherwise!!!! Go back and read the post. I said the Futaba site is outdated because the FCC license is no longer required. They got rid of a bunch of radio repair license requirments years ago, about the only things requireing licence is broadcast and aviation radios. However that does not negate the requirement that those repairs be made by a certified repairman. I believe that presently the certification is coming from the manufacture not FCC. And I still say the radio manufacture needs to start putting that crystal inside the radio! I am not so sure that the FCC can do anything about the user changing it, the reg is clear as mud on that. I did not say it is wise to change it.

I know you don't think I know what I am talking about, so I have linked where the FCC says when radio license is required.

http://wireless.fcc.gov/commoperators/wncol.html

Note you do not need a license to repair R/C. However you may not modify them, I think changing the crystal is a modification, at least if it bleeds into other channels.

RE: Crystals Failure?
 

Sport_pilot,
I'm not quite sure what you are looking at. You state that the only things requiring license is broadcast and aviation radios. If you are speaking about licenses to operate the radio then you are correct, there is no requirement by the FCC for us to have a license to operate our R/C radios. But this is not what we are referring to in the servicing of these radios. The FCC has not done away with thier requirements that I posted earlier in this thread. FCC Regulation 95.221 specifically covers having your R/C radio serviced. If interested you can find the actual regulation here [link]http://edocket.access.gpo.gov/cfr_2007/octqtr/pdf/47cfr95.221.pdf[/link]

This is the current regulation covering this matter and it is identical to what I posted earlier. The regulation states that the radios need to be serviced by somebody who is certified to perform the required work.
There is no confusion in the FCC regulations on this matter. If a crystal is changed in a RC transmitter in the United States it needs to be done by a person who is certified to work on these radios. This is required in order for the radio to be properly re-tuned to the correct frequency after the new crystal is in the radio. This is done for a very specific reason, and it has nothing to do with the possibility of interfering with somebody else's plane (although this is pretty bad in itself). The 72 Mhz frequencies that we use are very near other frequencies used for commercial purposes, television broadcasting immediately comes to mind although there are other uses as well. If a crystal is changed in a radio and it is not properly re-tuned there is a very real possibility that the radio will start to interfere with the commercial operations on adjacent frequencies. If this happens I can assure you that a visit from FCC officials isn't too far behind that. Fines for interfering with a commercial operation like this can range up to $10,000.

Trying to argue that this isn't required really does a disservice to those coming in to this hobby, and this is why we're not going to argue this point. Many just entering this hobby rely on this forum to give them accurate information, and many tend to take what is said in here are correct and accurate. That is one reason why we strive so hard to make sure that what is put out is correct here. So if we start arguing that this requirement on changing of crystals doesn't need to be done at a shop some may believe that and get themselves in trouble down the line. The FCC regulations are clear in this matter and we're not going to sit here and argue the point.

Ken

RE: Crystals Failure?
 

Sport, I know exactly what you are talking about, I have inside track to the FCC, which is why I posted. So Futaba used “licensed” instead of the more accurate certified/qualified phrase. You know what would happen if they said “qualified” instead of licensed… a bunch of peeps that jump started a car successfully once will believe they are qualified to change the xtal. I understand that technically the Futaba doc is wrong, so be it, the net perception is still correct in that users should not be changing their TX xtals.

RE: Crystals Failure?
 

The reg says certified, not license. The FCC has no such license, it states clearly on the link provide that it is not required. There is no requirement for repair licence for private land mobile services. So of course there is no such licence. Certified is not the same thing as a license. To argue there is just shows you don't know the differance. Read some of the posts in the radio forum. Actual technicians are saying the same thing.

Again I never said this was not so. But how do you get certified? Obviously not the FCC. They may be hanging their hat on factory certification.

RE: Crystals Failure?
 

Correct, per the regulation. I am not sure of the techical requirement, but that is another matter. But it is still wrong to have the crystals accessable, so I doubt anyone could prosecute someone for changing them. I wish they would rewrite this or stop certifying radios with accessable crystals.

RCKen, you may not like what I said above as you iterprete this as "leading the new user astray". But I have seen people chewed out for removing the crystal to prevent their transmitter from transmitting using a trainer cord with another transmitter. I understand some actually will transmit when using a cord. Possibly older radio's?

RE: Crystals Failure?
 

Sport_pilot,
I absolutely understand the difference between certified and licensed. I also understand that the Quote from Futaba's site may have mistated that the shop must be licensed. But, what I am trying to avoid is new people thinking that a radio does not have to go back to a shop if the crystal is changed. When you state that the requirements for a "license" has been removed some may mistake that for meaning that it doesn't have to be sent in to a shop. This is exactly what I am trying to avoid happening. When confusion is created like this it leads to somebody making the mistake and winds up in trouble because of that.

When all is said and done a crystal change in a transmitter needs to be done by somebody that can certify that they radio is transmitting on the proper frequency after the change, and retune the radio if it's not. Plain and simple, this must happen.

And yes, I agree in that I have seen people yell at other for removing the crystal. This is wrong and those doing the yelling are misinformed. There are no issues with simply removing the crystal, and in fact the same crystal can be removed and replaced with no issues to the radio. But if a different crystal (even one on the same channel) is placed in the radio it's output needs to be checked and retuned if needed.

As far as having the crystals accessible, this is a loophole that manufacturers have exploited. They will produce a case for their radios and they are sold worldwide. In most countries this is not an issue, but here in the US it is. The FCC regs stated (paraphrase here, not an exact quote) that the crystal can not be user accessible. So what the manufacturers did was to put a piece of tape or hot glue to secure the crystal in the radio, and unfortunately the FCC approved this as not being "user accessible". Yes, it's a loophole they exploited. But it doesn't override the need to send a radio in for service.

With all other considerations aside, it's just in a pilot's own interest to send a radio in if he changes the crystal. One of our members here (CGRetired) had a radio that the previous owner changed the crystal in. Instead of risking it he sent the radio in to have it checked. Since the radio wasn't retuned to the new frequency the radio was transmitting at about 1/2 the power it should have been. So had he flown with it he could have been at risk of losing his plane.


Ken

RE: Crystals Failure?
 

Well I send my radio's to Radio South, about time to do so again, they have changed my transmitter crystal once. I suggest that all do the same. It only costs something like $25 plus crystal as I recall and they check out the radio as well, even replaced a switch as I recall.

RE: Crystals Failure?
 

So... I thought that you could change the crystal(s) safely as long as you didn't go from the high band to the low band...

Is that incorrect? (note I've never had the need to change crystals, but this is what I've been told)

If not correct, they why in the world does futaba sell crystals to retail outlets like tower?

RE: Crystals Failure?
 

No, this is incorrect. Any change of the transmitter crystal needs to have the the radio retuned. Even if you put in a new crystal on the same channel as your old one it needs to be retuned. This is partially because no two crystals are identical. Because of this the output of the radio needs to be retuned so that it is transmitting on exactly the right frequency and the right output power.

Ken

RE: Crystals Failure?
 

okay, so why does futaba sell crystals via retail? seems like if it needs retuning whenever the crystal changes that they shouldn't sell crystals through retail, right?

RE: Crystals Failure?
 

This is true for the Receivers and the high/low only applies to some models of Futaba receivers. Transmitters are NEVER permitted. Possible exception are those in the amateur band but you MUST have an amateur license to utilize that band legally.

Tower (and other companies) will sell anything to anyone. It is up to the buyer to determine legality or get the equipment to a shop for tuning. Example: GM will sell you a car that will go 150 MPH (Corvette). It is up to YOU to determine if it is legal to drive that speed.

RE: Crystals Failure?
 

They are NOT the crystal police. They also sell worldwide where they do NOT have the same regulations. Regulations are different here than in other countries for many reasons one of which is that the frequency bands are more tightly packed with users. They also sell to shops. As I said above, it is up to YOU to obey the rules. It's not illegal to buy a gun. It is illegal to shoot someone. Should they make it illegal to sell guns? Or leave it the personal responsibility of the gun/crystal buyer? A big jump in logic I know but it covers the same issue. Maybe you want to need a permit to buy a crystal?:D

RE: Crystals Failure?
 

If you think there is a LOT of room out there for everyone you may want to think again. It's quite crowded

http://www.icta.mu/images/spectrum.jpg shows how the international community has divided up the airwaves.