Futaba T6EXAP

[Boots]

I have just bought second hand a T6EXAP  transmitter only, no rx.  I cant get it to operate any of my rx's .

My sunupp rx's say they are ppm but nothing works on either ppm or pcm.

I have a field strength meter so I know the futaba tx is transmitting .

I have a hitec focus 6 and a dynam neko 4 they both operate my   jeti, micron, corona,  sunupp and dynam rx's.

I have 2 sets of crystals.  ch72 supplied by micron as futaba compatible and ch 63 supplied by ripmax  for futaba .

 obviously all my radio gear works fine with each other.

 

I have never used a programable set before so I hope I have missed something very obvious in the instructions

[Brian Parker]

Boots, 

It should function straight from ‘switch on’ provided you have the correct modulation (PPM or PCM).

 Try clearing the model memory using the Data reset option (RCST) then setting the modulation using the ‘PULS’ option( It probably defaults to PPM).

 I have a T6EXAP.

 It lasted until the guarantee ran out then the RF decided to cease modulating-it’s still under the bench gathering dust, never got round to fixing it-useless.

Went back to my ancient JR Apex.

 Now on 2.4Ghz (non-Futaba of course).

Edited By Brian Parker on 07/12/2010 11:57:25

[kc]

Is it 35Mhz?   This TX was made in several other frequencies such as 40Mhz & 72 Mhz etc. Is the correct crystal being used? or wrongly marked?

I think you can find the manual online if you search, but I am sitting looking at the 6EXA.manual, ask if you want info.

 

There is nothing wrong with Futaba normally, its definitely one of the most reliable makes.

[Erfolg]

Boots

 

As a 6EX, 35 user (in addition to 6EX, 2.4), I have and continue to use other than Futaba Rx's.

 

To my knowledge, I use at least 1 Micron, a Weston (one failed), a Corona synthesised, a corona crystal Rx.

 

I possibly use and have used others, with no trouble with compatibility.

 

I would be suspicious of the Tx, if none of your Rx's work. Although measuring the output signal, rather than battery voltage suggests it is not the cause. Logic suggests it must in some way be the issue. 

[Barrie Dav 2]

Here in France 41...MHz is usual.  Perhaps the Tx you bought was ex France. (Someone returning to the UK). Are you sure that its a 35MHz?

[Boots]

Thanks for all the replys

I did " REST CLR" on all 6 models.

used my ch63 ripmax  xtals and still nothing

it has original looking labels , ripmax at base of aerial, on base of unit there is ripmax serial no. a " 35mhz " sticker and a futaba serial no.  sticker .  made in china ??

I will take it to the guy I bought it from on sunday and ask him to show it working ? I think he was using ch80

My guess is either it is transmitting off frequency or it is transmitting a carrier wave but there is no data on it.

 

Thank you for your advise and help full hints but  I feel the worst is true, its broken!!

[John Tee]

Hi Boots

 just a thought are you using dual conversion crystals,.

 

John

 

[kc]

Surely the dual conversion crystals are only used in the Rx, the Tx crystals are all the same.

Get your money back if it is not working!

However do not scrap it because it may still be useful as a buddy box, especially if it has the square type buddy lead socket which means it could be used with any of the later type Tx as a buddy box. ( if enough of it works! )

[Erfolg]

Ahh, I get it, I think.

 

You suspect that either the Rx or the crystal is a dual conversion item, and the other is not.

 

Could be, a possibility.

[CARPERFECT]

When you switch on, look at the top right hand side of the display screen. it should say PPM. If it is showing PCM you need to change it. If you do not know how. reply back and i will tell you

[kc]

No, surely the dual conversion crystals are only used in the Rx ?  Transmitters use just normal crystals no matter whether the Rx is single or dual conversion.  ( dual conversion Rx must use the dual conversion crystals )

 

Also you must use a Tx crystal in the Tx and not a Rx crystal. Futaba ones are marked Rx and Tx ...I have just checked my 6EXA they are marked and only the Rx crystal is marked dual conversion.

Edited By kc on 08/12/2010 11:42:34

[Erfolg]

The dual conversion refers to the Rx only. A  dual conversion Rx needs a dual conversion crystal. How you tell the difference in crystal types others will probably know.

 

What you cannot do is mix single conversion bits with dual conversion bits.

[kc]

Dual conversion here is a red herring!   If the Rx has the correct crystal it should work with this Tx if the transmitter has the correct frequency Tx crystal.  That is to say if the Rx works with another Tx then it should work with this Tx ( on the same frequency ) .   If not the Tx is faulty in some way.

 

Futaba dual conversion Rx crystals have "dual conversion" printed on the label.  Also the Rx.

[Erfolg]

Kc

 

You are of course correct in what you say.

 

We understand that Boots has a problem.

 

Do we know that the Rx Boots refers to actually does work with another Futaba Tx?

 

As an issue it needs eliminating.

Edited By Erfolg on 08/12/2010 15:53:00

[Paul Newell 2]

Not familiar with the workings of this particular Futaba transmitter but having designed equipment in the past and done a reasonable amount of fault finding on various makes, to me it sounds as if the modulation has failed.

 

You can get a correct reading on a field strength meter but it could well not have any modulation or not be applying the modulation correctly to the RF signal.  This can really only be checked with a spectrum analyser but I guess that most people will not have access to such equipment.

 

Have seen exactly this problem recently on an old Tx from a now defunct manufacturer and actually found the problem to have been caused by corrossion on the pcb.

[Brian Parker]

Paul, Agreed, a modulation fault (see my posting above).

 

Boots,

 If you’ve reset the transmitter to de-fault settings, are using the correct compatable transmitter and receiver crystals, the correct mode and the field strength meter is detecting a carrier then it is a modulation fault.

 Wasn’t impressed (compared to JR) when I opened the back of mine, that’s why it’s still under the bench.

Edited By Brian Parker on 08/12/2010 19:37:46

Edited By Brian Parker on 08/12/2010 19:38:03

[kc]

Wouldn't it still work as the slave in a buddy box set up even if it has a modulation fault?  

If so and it has a rectangular buddy lead socket it will work  even with 2.4 Ghz Futaba Tx in a buddy box set up.   That is to say even 35Mhz Tx will work as a slave to 2.4Ghz  ( see Futaba website )

So it will not be completely useless, but i say you should reject it & get your money back.  If necessary ask your local Trading Standards dept what rules apply to private sales where the goods do not work.

Edited By kc on 09/12/2010 11:38:55

[Boots]

Well lots of info.

yes it is set to ppm as all of my rx are older or cheaper types.

dual conversion xtals not the problem as the tx xtal is the same it is the rx xtal which is different frequency  due to the dual "  IF" stage .

I had never played with buddy box leads before last night.  I can now use my Hitec focus  as the master and connect either  the dynam neko or the t6exap and use them as slaves.

 

This has proven the encoder in the t6 is working,  I know the tx is generating RF, BUT my rf meter is very primative so It cannot tell me at what frequency it is, 30to 40 meg I guess???? and if the pwm signal is be modulated onto the carrier. I have a Micron "Transmitter power meter" model tp35 a simple but useful tool

 

What if I am mistaken about my xtals  Futaba compatability ????

 

still things I have gained sofar.  I can now buddybox with a friend I am helping learn to fly. My Dynam neko 4 is a 6ch tx , just needs me to fit 2 more knobs.

improved knowledge when buying s/h equipent......check it first

still I hope to see the guy sunday and I am sure a solution will be found.

Be an optomist........It is good for your blood pressure

 

Also the xtals you buy are labelled with the std frequency for that ch, it does not mean the xtal is that frequency, for example many moons ago I built the RCM&E 35mhz fm transmitter, worked perfectly too, it had Fleet xtals and the tx xtal for ch76 was 17.5976 mhz and the rx xtal 34.705 even though ch 76 is specified at 35.160 mhz

 

[Brian Parker]

Boots, 
I was under the impression that you were using a Futaba TX crystal.

 If the TX crystal is not a genuine Futaba crystal then that could be your problem.

 As you have discovered, the TX crystal oscillates at the frequency required by the RF exciter stage to produce the required output frequency. That’s why TX crystals are not usually interchangeable between manufacturers.

 RX crystals are interchangeable in single conversion PPM receivers regardless of manufacturer. Dual conversion receivers have two crystals, one internal and the one we change to achieve the required channel.

 Hope you get it sorted.

[Peter Beeney]

   Brian,
             Can I post a little view just for interest.

   I’ve dabbled a bit with changing crystals around in radios, over a fairly long time, usually for training purposes. I have a few MPX crystals, which I tend to use as much as possible, simply because I like the kit! I have an old Skysport tx for training which has always had a MPX xtal, certainly for at least 10 years. I would consider that any tx, if transmitting on say, channel 77, would have to be transmitting a frequency centred on 35.170 MHz. Thus the required frequency would always be 35.170 MHz. Irrespective of manufacturer. My MPX tx crystal has markings thus, 77, FM, and 17.585. From this I deduce that the crystal oscillates at half the required frequency and the times 2 harmonic frequency is then used to obtain the necessary 35.170 MHz. I think Futaba must use the same system, because MPX crystals always seem to work well with Futaba. As they also did with my old Skyleader, too. From somewhere I seem to think that JR use the 3 times harmonic, but I’m probably quite wrong on that score.

   My single conversion rx crystal is marked 34.715, and so I deduce once again from this that the IF (intermediate frequency) is 455 kHz. 35.170 - 34.715 = 0. 455. Again, I feel that Futaba must be similar, because it works so well. As with many other rx’s, too, and as you say, generally they seem to be interchangeable. However, one single conversion rx that doesn’t play ball is a Hitec; or, at least the older Hitec, and not with us anyway. I don’t know about the newer ones. We found they would only accept the genuine Hitec rx xtal. Maybe they use a different IF, 470 kilohertz is one that is sometimes used, I believe. The dual conversion crystals don’t seem to be very interchangeable, this is total speculation on my part, but it’s possible that they might use different 1st IF frequencies, 10.7 MHz is one that is used, perhaps. I use a little cheapo Corona DC rx, with a Futaba crystal, I don’t think Corona have their own, and this seems to be totally bombproof.
   Very recently a beginner turned up with a budget GWS radio in a trainer, and this had a little odd glitching problem, not range connected, just a bit of odd noise getting through occasionally, I thought. The GWS had no buddy facility, so I used the Skysport tx and the MPX rx crystal. This instantly solved the little glitching problem, which was nice. It might have been a bug in the GWS tx, but I have a feeling that it was the rx.

   I would be tempted to try MPX crystals in anything, if it works, it works, subject to some stringent pre-flight checks, of course. I’ve only ever had one fault with MPX, a filter on a little Pico rx. I sent it back to Germany and the next minute the man’s found my phone number, rung me with the description and cost of repair and to arrange payment plus telling me they were sending it straight back. Good customer relations, I thought.

   Finally, one way of checking the modulation might be to listen to it on a scanner. I’ve had one for years, looking for interference on 35, which I’ve never found, so I don’t bother trying any more. However, you can hear the modulation run up and down on the carrier as you waggled the sticks. With practise, you might even be able to play it!

   I like MPX radio, but I have to say that the Futaba bits are just as good! I can’t fault it.

   PB        

                                         

[Erfolg]

I keep watching this thread, and do not know if any progress has been made.

 

An example, do we know that the Rx being used, actually works with another transmitter. Or better still a Futaba 35 Tx.

 

[Brian Parker]

Absolutely Peter, it’s in the harmonics. I was attempting to keep my posting non-technical.
 The 455Khz and 10.7Mhz IF frequencies are pretty much standard, also a 17.xxMhz crystal is far more robust than one oscillating at a higher frequency and it is easier to keep it ‘ringing’.

 I’ve never had any problems using various makes of receivers with either JR or Futaba transmitters and generic RX crystals.

[Boots]

Thankyou Brian Parker and Peter Beany

 

I am sure the guy I bought the radio from is a genuine person, I see him regularly at the field.

I was also sure one set of xtals were futaba genuine and the other set futaba compatible, but I had tried everything and no luck so I was begining to suspect the xtals, what else could it be ?

I still have a set of Fleet xtals used in the rcm&e 35mhz project about 1990 I think. the tx xtal is a half frequency type and BINGO !!!!!!!!! the futaba tx works well yipeeeee !!!!!

Just goes to prove that when you are sure of something ,,,,, how wrong you can be.

 

Still, I now have a pc oscilloscope and know most of the connections on my futaba, hitec and dynam tx buddy sockets and have leads made up so I can use the Dynam as a slave and the Futaba and Hitec as either master or slave 

I am working on a buddy lead to use my MacGregor Digimac 6 (1980ish) as a slave, the encoder works but the rf stage is unstable, and is 27Mhz anyway also hope to make an FMS interfacs lead

 

I did not have a complex problem but it is good to discuss things with others.

 

subject to successful range testing I will fly with the fleet xtals.

 

Thanks to all for your comments

 

[Paul Newell 2]

To the best of my knowledge Futaba and Fleet single conversion crystals are the same spec.  As the designer of the Microtrol system published by Radio Modeller back in the distant past, either could be used in my design..  Whilst the TX6EAP could well have a different form of RF circuit to earlier designs it is unlikely that Futaba would have changed the spec of the crystals.

 

It is all to do with the harmonics but also the nature of the capacitance of the circuit into which the crystal is inserted. - i have some Graupner crystals which worked OK in my circuit BUT produced the signal at a frequency midway between two official channels.  This is why it is stated only to use the manufacturers crystal in a given transmitter. Receiver crystals are different and far less critical.

[Peter Beeney]

   Boots,
          Thank you for your reply. I’m pleased to read that you’ve cracked it ok! The only Fleet radio I owned was a Mini 4 channel rx, which was ideal in powered gliders, but still using the ubiquitous MPX crystal, of course. As I remember it tended to keep you on your toes, because the Fleet servo pin schedule made the centre pin negative and an outside one positive. This meant that to use other brands of servos you made an extension lead with a cross-over, otherwise you could get a bit of a reversal! This was another situation where the old maxim ‘measure (voltage!) twice, plug together once’ proved invaluable. They also did a kit to make your own servos, this was exactly the same hardware as the Skyleader servos, but the Skyleader’s were made up of course; they were all interchangeable rotary or linear output, just by changing the tops. I made a number of these for fellow Fleet pilots. As a little pointless aside, at one stage I cut the backs away to modify the stick gimbals on my Skyleader tx to get more servo movement, so I also had to file out the slots on the linear servo tops to allow for the extra travel. When I later met Stewart Uwins, Skyleader’s MD, at a model show, and told him what I’d done, he gave me a little wigging! Understandably and deservedly so, I think. With hindsight, I think the fact that it always carried on working ok after that once again proved the sheer good quality of some of the bygone radio equipment.

   I agree with Brian, crystals seem generally interchangeable, although when I tried a Futaba crystal in the MPX tx, (the reverse of what I normally do) that gave me some small glitches. Off-tune slightly somewhere, maybe. And as always things are not always what they seem. I was given a crystal of unknown origin, as faulty, clearly marked 61; however, when I tried it on the scanner it came up clearly as 62. This could have resulted in a frequency clash, although probably very unlikely. However, if there’d been a rx xtal to match…….. I was going to try and find someone on 62 to give it a practical test, but I never got around to it. One trick I did learn, a long time ago, for new members and especially beginners, always take the rock out of the tx and check it; irrespective of what they tell you or what it says on the crystal holder! They do not always concur!

   The problem I have with buddy leads nowadays is the plugs. It seems that the Futaba square plug is not available on it's own so the only way to change one end is to either carve up a new lead or buy the proper one in the first place anyway. I made a Spektrum lead, using phono plugs which only half worked, even to the extent that changing over the master/slave configuration was the difference between working or not. My mate bought a ‘genuine Spektrum’ lead on eBay, which was virtually the same. Then I bought a Spektrum lead, which did work. Looking carefully at the phono plugs, they are all different, it’s the shape and sleeve length which causes the problem, but only by a millimetre or so across all three. We now seem to be walking along a very narrow road.

   Bring back the multi-pin round DIN plugs, I say!

   Hope it’s all a success!

   Paul,
        If using non-manufacturer's crystals in a given tx, such as I do, I’m fairly convinced that this doesn’t necessarily always send it off tune. Surely this would give the rx some headaches, to say nothing of any possible adjacent channel interference. I’ve never had the slightest glimmer that the tx is off tune in any way. Not only that, many of the crystals that I see are the standard no-name pattern ones that model shops sell. For any make of tx. Who makes those? And are these always accurate? With the ever increasing use of 2.4, this stuff is fast going out of the window anyway; all the newcomers are buying 2.4 gear, I think soon there will only be a few old stalwarts on 35! And it’s just struck me that I’m now into the 2nd overtone myself, still, it’s only after the 3rd that the harmonics really start to fade away, I believe.

   I fear my oscillations already may be already losing some momentum……

   PB