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Robbe receiver

Help needed on connections

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Trevor Longstaff23/09/2021 15:31:32
3 forum posts

I'm returning to model boats in a small way after quite a few years away. I still have operational 27mhz gear which I intend to use but have had to replace a defunct receiver with a Robbe unit. My simple question is - which socket on the receiver is for the battery connection? The three 3 pin sockets are labelled Dr., Sel. and Ak. which mean nothing to me.

Colin Bishop24/09/2021 19:01:08
4988 forum posts
6114 photos
412 articles

All the sockets are likely to take a battery connection. You don't say how many channels your RX has but there will be at least one each for throttle and rudder and a third for battery, possibly the one 'at the top'. A bit of experimentation using servos should establish which is which.


Malcolm Frary26/09/2021 08:57:06
1040 forum posts

Being Robbbe, the markings are likely in German. At a guess, "AK" is short for "akkumulator". Maybe Dr for direction? or maybe drive?

Channel 1 is traditionally steering, and is usually the furthest away from the battery connection. Throttle is the one in the middle. Normally receivers use the outermost connection pin as the black/negative/ground line with the next inboard being red/positive line. These pins are usually common across the rows, only the innermost pin on the two columns is unique and carries the signal for that channel.

If using an ESC with a BEC, you don't need to use the battery connection anyway, it's been done for you.

Trevor Longstaff02/10/2021 15:31:52
3 forum posts

Thanks for the advice - Ak is indeed the battery connection. I will be using batteries at least for the moment. The model I am working on is a Duplex TID tug from the 1980s. It has a Bob's Board speed controller - remember them? I had intended to replace it with a RCLine Sea Rover 15A controller; will this work with 27mhz gear? If so there is a connection compatability issue.The Robbe receiver takes 3 pin male plugs but the Sea Rover has a 2 pin female plug. Is there an adapter to convert one to the other? I cannot see any likely candidates online, and my local model shop was no help at all. In fact he's never seen nor heard of Futaba 3 pin connectors. I am reluctant to try to rig up something myself at the moment but accept I may have to. Or I could resurrect the Bob's Board to retain the period feel!

Malcolm Frary03/10/2021 09:44:30
1040 forum posts

No experience with this particular EC other than what a google search has turned up. From the very scant information, it has no BEC, so needs a 5 volt input, the red 2 pin does that. It has the conventional pair of big thick wires for main power, and two more for motor connection.

The weird bit is the signal connection. Most manufacturers use a 3 pin connection that caters for both control power and signal. This one uses a 3 pin receptacle, but only the outside two points. Presumably black for ground and white for signal.

So, on a modern radio, the radio battery would plug into the "Batt" or "Ak" hole, the signal plug into the preferred channel, the steering servo into the chosen channel for that, and the ESC red plug into a spare channel to give control power to the ESC.

Unfortunately, with a 2 channel set, there are not enough slots, so a choice needs to be made.

1 Get a Y lead. Plug it into the throttle channel, plug the black two (3 connection, only 2 used) pin into one leg, the red power into the other. This might entail a bit of minor surgery on the red plug, Y leads are generally intended for flat plugs. Receivers have pins, the plugs that fit them are usually shrouded receptacles, thus technically, sockets. I tend to wait for a show and go to the Component Shop stand for things like that. Or, over the last couple of years, mail order.

2 Winkle the red wire out of the red two pin (assuming that its a floating socket) and insert it into the centre hole of the black three. This will cause it to be wired like every other ESC on the planet.

3 Go modern radio. 2G4 sets tend to start at 4 channel with a 6 channel receiver and cost less than a replacement second hand 27MHz receiver.

4 Get a more conventional ESC. Mtronics and Quickrun spring to mind. Unless you already know that the Bobs board is a perfect match to the motor, vastly better control will be had with an electronic unit.

I have no notion of why the makers thought that this was a good idea without illicit substances being involved, but there might be a reason in there somewhere.

Charles Oates03/10/2021 12:09:37
642 forum posts
52 photos

I was wondering how an esc could work with only 2 wires. I can't help wondering if Trevor wouldn't be better off ditching the 27 meg gear, some of the components must be at least 40 years old. A new 2.4 gig outfit could cost less than 30 quid. No interference worries, no problems plugging modern servos and escs in and little chance of failure.

It's something to consider.


Colin Bishop03/10/2021 13:48:01
4988 forum posts
6114 photos
412 articles

Charls is right, trying to integrate a bunch of components that were never designed to work with each other is quite likely to be both frustrating and expensive.

There is no particular virtue in trying to restore a 27MHz system that isn't working.

I have a couple of boats still on Futaba 27 MHz but if a fault does develop I will replace with 2.4GHz gear.


Charles Oates03/10/2021 15:26:08
642 forum posts
52 photos

If I've guessed correctly, the receiver is the old kompakt one, it pre dates the kind of connections that have been used for decades. The receiver has sockets, and the servo plugs have pins, a system that dates, I think from the 1970s. Trying to use that today with adaptors or changing plugs seems far from wise to me.


Trevor Longstaff05/10/2021 16:34:53
3 forum posts

Thank you all. I suspected that old school and modern systems would be largely incompatible and you have confirmed this. As I am fixing up old models largely for use by my grandson, whose interest may well be transitory, I wanted to make as much use as possible of my ancient equipment and not spend on new if avoidable. I will therefore see what I cam fashion from what I have, and should it turn out that I need to buy new I will have to bite the bullet and sell a spoon or two from the family silver.

Malcolm Frary06/10/2021 09:55:32
1040 forum posts

It is rarely reliable trying to join different generations of RC together. My first radio was a Maplin brand one. Servo plugs in a very substantial housing (industry "standard" "Molex", maybe) but had the pins on the usual 0.1" spacing. But with the three sets of connections in one row across the receiver. "Modern" low profile plugs would fit.

Apart from a couple of old Futaba servos I was given, which had pins and unequal spacing. The copper tube adaptors worked but it was, at best, a bit iffy. If the receiver had had receptacles rather than pins, pins could have been easily created by using the right size nickel silver wire, but would still have had that bit of uncertainty.

Then there was Sanwa, who kept to the expected mechanical standards, but shuffled the pin order. Everybody else went -,+,signal. Sanwa didn't, and if you mixed without rearranging the wire order, you had a reverse connected radio battery. Thankfully, nowadays everybody has settled on one standard of plug layout, any manufacturers foibles of using locating key tabs can be cured with a sharp craft knife.

I don't know what the signals were on the old 4 wire servos that I have heard of, but since before I started, everybody has worked to the same signal standard, so if the wires can be plugged in in the right order, it will work.


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