Futaba 7C / Hitec Laser 4 trainer cord - how? - RC Groups
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Nov 23, 2004, 03:56 PM
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Futaba 7C / Hitec Laser 4 trainer cord - how?

Hi all,
This Thanksgiving I'll be at my inlaws house, and there may be some young people present; I plan to take along one of my RC planes, and would like to set up a buddy-box system so anyone interested can try flying it.

I have a new Futaba 7C Tx that I would like to use as the master, and my old faithful Hitec Laser 4 would be the slave. To my knowledge, these two Tx's are compatible for this use (both negative shift, same channel assignments on Rx), but I have never used a buddy-box (or seen one used, even!).

Questions: What exactly do I need to do this? Where can I get the weird connector Futaba uses on their Tx? Will the slave (Hitec) disable its own RF output stage when the buddy cable is plugged in, or do I have to pull the crystal? If I know exactly what to do (pin numbers, schematic diagram) and can find the appropriate connectors, soldering up a cable is no problem.

Thanks in advance for all replies and help.

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Nov 23, 2004, 04:14 PM
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Hi Flieslikeabeagle,

You would need to purchase FUTM4420 which retails for $14.99. This would be to use the Futaba as master and the Hitec as slave.

You will want to first set your trims on both radios as close as possible, and then you can remove the battery and crystal from the slave radio.

I hope you find this information helpful. You can also reach our Futaba support technical team at 217-398-8970, or via fax at 217-398-7721.

Lead Futaba Customer Service and Programming Technician
Nov 23, 2004, 06:15 PM
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Krysta, thank you for your reply. I will try to locate the FUTM 4420 locally.

My understanding is that the RF section of the Hitec transmitters can be disabled by shorting two of the pins on the Hitec buddy-cord connector - I take it the FUTM4420 does not short those two pins, as it is not designed specifically for the Hitec?

Nov 28, 2004, 06:51 PM
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Warning! Don't use the FUTM 4420 cable with a Hitec till you read this!

Okay, I did a little more research, and what I found was a little annoying. Firstly, the Futaba cable (FUTM 4420) firstly does not disable the Hitec RF output stage, so you have to remove the battery pack from the Hitech slave Tx, as Krysta said. But I also found that the Futaba cable is not entirely compatible with Hitec transmitters, having in some cases damaged components inside the Hitec slave Tx and/or Futaba master Tx

Take a look at this URL for the details:

The fix is simple, simply make up a cable with only two wires, one connecting the ground of each Tx together, and the second connecting the PWM output of the Hitec to the PWM input of the Futaba. By avoiding the battery+ wire, there is no risk of parts burning out. And if the appropriate two pins are shorted together at the Hitec end, then there is no need to remove the battery or crystal from the Hitec Tx either, as its RF stage will turn off when the buddy cable is plugged into it. The pinouts are at the same website: to quote, "make yourself a trainer cord as described in fig. 7f-03 of chapter 7, it's the simplest and without risk."

So why am I annoyed? Because of that stupid Futaba proprietory connector. Now I have to fork over around fifteen bucks to buy a Futaba cable that isn't safe to use, simply in order to get the weird Futaba connector, and then I have to fork over some more bucks to buy one female and one male DIN 6-pin connector, and then I have to make my own cable, wiring them together to make an extension to the Futaba cable that only carries the PWM and ground signals between the Tx's.

Just to be clear, this is not a rant at Krysta, who has been knowledgeable and helpful. It is a rant at Futaba's decision to use a non-standard connector on their Tx's, simply to squeeze a few more bucks from customers wallets. It is an ugly business practice, reminiscent of Microsoft and their constantly altering MS Word file formats that force users to constantly buy newer and more expensive versions of Word.

Jan 20, 2005, 10:05 PM
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Did you get this setup to work? I want to buy a Futaba 7C or 9C and use my Hitec Flash5X as the student.

Any help is appreciated.

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