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Futaba T6EXAP

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Boots06/12/2010 22:00:39
113 forum posts
8 photos
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 Parker07/12/2010 11:56:29
538 forum posts
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

kc07/12/2010 12:06:07
6291 forum posts
170 photos
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.
Erfolg07/12/2010 12:28:52
11654 forum posts
1297 photos
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 207/12/2010 12:38:40
1012 forum posts
14 photos
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?
Boots07/12/2010 17:50:02
113 forum posts
8 photos
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 Tee07/12/2010 18:18:34
815 forum posts
65 photos
Hi Boots
 just a thought are you using dual conversion crystals,.
kc07/12/2010 18:54:34
6291 forum posts
170 photos
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! )
Erfolg07/12/2010 19:10:40
11654 forum posts
1297 photos
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.
CARPERFECT07/12/2010 20:10:25
504 forum posts
9 photos
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
kc08/12/2010 11:32:37
6291 forum posts
170 photos
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

Erfolg08/12/2010 15:31:37
11654 forum posts
1297 photos
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.
kc08/12/2010 15:43:31
6291 forum posts
170 photos
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.
Erfolg08/12/2010 15:52:31
11654 forum posts
1297 photos
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 208/12/2010 16:50:36
40 forum posts
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 Parker08/12/2010 19:37:09
538 forum posts
Paul, Agreed, a modulation fault (see my posting above).
 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

kc09/12/2010 11:29:37
6291 forum posts
170 photos
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

Boots09/12/2010 23:36:12
113 forum posts
8 photos
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 Parker10/12/2010 04:47:14
538 forum posts
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 Beeney10/12/2010 18:42:23
1587 forum posts
59 photos

             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.


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