Futaba M Series 27 to 35

[rossi46]

Hi,

I am thinking of converting my old futaba M series to 35 Mhz using the circuit board from a futaba FP-T4L. I was looking for any advise on this.
I can solder/use a multimeter. I am not bothered about losing channels 5 & 6. Also its going to need a good clean and I read on this forum about using mountain bike cleaner. Any help with this would be great.

Thanks Stephen

[Tobe]

Welcome to the forum,
You sure have a lot to clean not least as there's quite a lot of corrosion and probably switches and pots would also need some attention but it has been done before and successfully.
Instead to swap the boards I would recommend one of the encoders shown here on the forum which would give your converted Tx really a new modern life and depending if you like to go for 2,4GHz or keep it 35 MHz it's only a matter of what RF-module you choose.
All instructions are available for the DIY and if you have issues we sure can help you.

Cheers

Tobe

[rossi46]

Thanks for the reply I want to retain the aerial to maintain the retro look. I do intend to try one of the encoders on another transmitter I hope to convert

[bluejets]

I want to retain the aerial to maintain the retro look

Won't work on 2.4gig.

[Tobe]

PaulJ keeps the aerial by hiding it in the frequency flag.
viewtopic.php?f=24&t=1019&p=8525#p8525

[Wayne_H]

PaulJ keeps the aerial by hiding it in the frequency flag.
viewtopic.php?f=24&t=1019&p=8525#p8525

I've copied Paul's idea on several Tx conversions, and the range has been as good as ever. Thoroughly recommend it

[Mike_K]

You probably could convert it to 35MHz, but there are a few issues you'd have to overcome.

If you really want to keep the Futaba M6 on 35MHz, the best option would be to fit an original 35MHz circuit board, Futaba did some 35MHz M series sets (brushed alloy silver case, not the beige vinyl clad like yours) and also a couple of manufactures did aftermarket 35MHz conversion circuit boards (I think Viking were one?), these were the same shape and size as your corroded circuit board and are an easy swap. I may have a spare Futaba M6 35MHz board from a conversion I did a while back (I can't remember if it was corroded, if it was I'd have binned it), if I've still got it you're welcome to it. I wouldn't worry too much about the pot's being corroded, they were sealed units and I've never seen one fail, even when the transmitter was more corroded than yours, but I would replace the power switch, it has 28mm fixing centres and there are new equivalents that should fit:

https://www.technobotsonline.com/dpdt-s ... -0.3a.html

The downside to fitting an original 35MHz board is that you would have to adjust the M6 timings, they were slightly different, the ppm outputs were 1.3mS centre, not the modern 1.5mS, though the M6 board does have adjustment trimmers for each channel and there is usually enough adjustment to get them to 1.5mS (I assume you don't want to use the original servos). The transmitter would then work with a modern Futaba 35MHz FM receiver.

The FP-T4L you were considering has a NE5044 (or equivalent) encoder chip with servo reversing. It had the joystick pots centred when the joysticks are neutral, whereas the M6 had the pots about a quarter way (a joystick only moves the pot around 60-70 deg of the total 300deg rotation), so to get the FP-T4L to work, you'd have to partially disassemble the joysticks and rotate the pots to centre, which is a pain to do, but it would then work, including the servo reverse.

But if it were mine, I'd do as everybody else suggests and convert it to 2.4GHz with a modern Arduino-based encoder and a LemonRx or FrSky 2.4GHz module...

[rossi46]

Thank you everyone for replying and the helpful information. Certainly alot to think about. I have started cleaning the case and its looking alot better now after 30+ years in my mums loft Thanks again.

[Pchristy]

A quick note about Mike's suggestion to use the 5044:

The 5044 is a very good and simple encoder. However, it does have one flaw! It is VERY prone to RF pickup - ie: the neutrals shift markedly as you put the aerial up and down! No amount of decoupling capacitors will cure this!

The only way I found around it was to use a double-sided PCB, with a ground plane on the component side. This worked perfectly - even at 459 MHz!

--
Pete

[Wayne_H]

The only way I found around it was to use a double-sided PCB, with a ground plane on the component side. This worked perfectly - even at 459 MHz!
--
Pete

IIRC, the double sided PCB with ground plane was exactly what ACE did with the Silver 7. I can't check either of mine since they are packed away with the rest of my gear & projects while house building .