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[Joe Hardy]

Hello
I wonder if  some kind soul can give me the circuit/ mod. which will enable me to add a third function to my Futaba FM 40 Mhz Attack two function transmitter.
I have a three function receiver and I need to operate a third servo to make and break a simple motor cicuit via a micro switch.
I have seen a modified transmitter with an on /off toggle switch mounted on the top of the  case. But the owner had not done the mod himself
Any help would be greatly appreciated
Regards
Joe

[cbr900]

Have a look on the old ebay quite often cheap radios without recievers....


Roy

[Daryl]

Or try Howes of Oxford they sell transmitters seperatley and are quite cheep. Good service when I 'phone before 3pm its normally delivered the next day.

Daryl

[Joe Hardy]

Thanks guys. I already possess Four and six function outfits. The addition of a simple switching circuit would be a neat solution to my current installation
                                                                                    Joe

[barriew]

You can achieve this using one of your existing channels and a switcher unit from say Action kits. Usually you use the steering channel and when you 'flick' the steering stick it operates the switcher unit. No Tx mod required.

Barrie

[Joe Hardy]

Thanks Barrie.
I had considered a switching unit but I suspect the mod I have seen is much simpler. Still if all else fails............
                 Joe

[barriew]

I don't see how a Tx mod alone will solve the problem - you would also need to mod the Rx or use a 3 channel Rx.

Barrie

[BarryM]

What this thread throws up is how difficult (impossible??) it is to find somebody prepared to offer Tx/Rx servicing and mods. Somebody is missng a trick in a niche market here.

[Joe Hardy]

Barrie you will notice by my original post that I do have have a three function receiver.The daft thing is that it was included in a Futaba 40 MgHz 2 function outfit as standard.
Yes Barry I agree there is a niche for small mods but I suspect like getting someone to do little jobs round the house ..........
I know that I can get this extra function added by a fellow club member who is a computer engineer (he has produced some super gizmos in the past )
The problem is that we never see him because he is always snowed under with work.
I let him have a printer to service last Winter and I am beginning to wonder whether I will ever see it again.
Hence my query

[riggers24]

Hi Joe,

Why don't you look for a Hitec 3 channel set on eBay, I have heard of them been converted to 4 channel.

Marc

[malcolmfrary]

Looking back at the original posting, Joe Hardy has a two channel Futaba Attack 40MHz TX, and a 3 channel receiver, and has the impression that there is a third channel available on the TX for a simple mod.  I have doubts that in this day and age of careful costing, that the third channel is that easily available on the TX.  The simplest way would be, as other replies have said, to buy an appropriate TX, 3 or more channel. 
My understanding from previous threads of how these things work is that unaccounted channels are simply ignored by the RX, so a 3 channel RX should have three chaanels from a four channel TX, its just that the 4th channel does nothing.
It is also possible that the modded TX he has seen has a switch that puts a short "full rudder" on the steering channel, enough to operate a switcher, but not enough to make the servo react, so it is still really a 2 channel set, but with three functions.

[Joe Hardy]

Thank you for your interest Malcolm
I can assure you that the transmitter I am referring to works as follows.
Right hand stick rudder.
Left hand stick sail servo.
Set top switch operating a motor via a servo operated microswitch.
If you are familiar

[Joe Hardy]

Sorry Malcolm
Lost the thread.
If you are familiar with the old Futaba M series six function transmitter you will remember that the undercarraige retract servo was controlled in a similar fashion by a set top toggle switch
I could of course use my four function outfit but I enjoy a challenge
                        Joe

[justboatonic]

Lots of places sell just the TX, example Modelsport UK. However, I think 3 channels are a (fairly) rare breed. Given the cost of a 4channel tx only, this would make better sense if only for the integrity of the transmitted signal.

I once added a rate kit to a 2 channel Tx but I've never seen a 3rd channel kit for a Tx.

[Doc]

FWIW
Don't know about in the UK, but here, modifying the transmitter is a 'no-no'.  It's possible, but it really isn't a simple modification, adding another discrete channel.  Changing the 'way' an existing channel operates is also possible (not always simple though, just depends on the knowledge/experience of the modify-er).  There's no problem about modifying the receiver, just with modifying anything that transmits a signal.  The FCC would require that the system be re-certified and approved($$$).
 - 'Doc

[martno1fan]

no bull s**t doc!!

[Jankers]

Hi Joe,

I think the mod you have seen is possible, but only on those TX's which were
produced for 3/4 channel use and pressed into service for the 2 channel outfits. In those circumstances i have seen threads (no circuit) whereby it was possible to 'resurect' a third channel.

if i remember correctly, it applied to a particular model of TX produced as an updated design when the older (4ch) boards were used up to get rid of them.

It ws some time ago now and I no longer have the details.

J.

[Joe Hardy]

Thanks Jankers
I have just found out that a fellow club member has had this "surgery " done on his transmitter.Iwill twist his arm with the hope that he will let me see inside his transmitter.
If this  solves the problem I will let you know
  Joe