Gate Merf 3.2 not working correctly? F2000 semi-auto trigger not working

[RostokMcSpoons]

In preparation for a couple of new 11.1v batteries arriving for my F2000 (already upgraded with full cylinder, hi torque motor, better spring), I've bought and installed a Gate Merf 3.2

I've taken the front (left) trigger wire and moved it to the connect at the rear contact, and installed the single signal wire to the now open contact.

I've programmed the MOSFET for the 11.1v LiPo battery, but everything else is at the defaults.

It fired.  It fired full auto at 19rps. Nice'n'snappy
And then it stopped. 

I took it all apart again.  Put in the new piston which I'd already found has less of an airseal, but had the correct piston head to go with my new cylinder head. 

And then it fired again.

And then it stopped.  Recharged the battery (from 10% charge, 3.60v each cell, which didn't exactly scream 'battery voltage too low' to me)

And then it fired again.

And then it really jammed up.  Might be my fault, maybe I didn't tighten up the screw enough but the piston head came away and broke the rack.  

I took it all apart again.  Refitted the old piston.  Radiused the gearbox shell too.

And then it fired again.

And then it stopped.

It always fires with the programming trigger connected, but when I go back to the signal wire / gun trigger, it doesn't always fire again.
The signal wire looks fine, no obvious pinches on it, the solder is secure.

The fact it has sometimes fired again after a delay makes me think of a thermal cut-out, but everything has only got slightly warm after the few bursts I get to fire each time.

I guess I'll re-solder the signal wire, but is there anything inside the trigger unit that might have gone awry too?

 

[Iceni]

Your wires should look like this. Cut on the white crosses.

View attachment 84950

I've taken the front (left) trigger wire and moved it to the connect at the rear contact, and installed the single signal wire to the now open contact.

I think what you've done is use the signal wire to carry full current, hence it shutdown.

The diagram above with the double signal wire directly to what is now an isolated contacts circuit.

The motor directly to the Deans, as an isolated motor circuit.

If it's still working on the program button then you should still be good.

There was no need to move any wires at all. Damn I wish you would of just asked for a diagram before you started.

 

 

[RostokMcSpoons]

Thanks Iceni, I'll consider what you have shown, but my method is as per the Gate instructions...

https://www.gatee.eu/images/gate/instrukcje/merf32-en.pdf

Section 2a, which specifically says the signal wire only carries a small current

 

[Adolf Hamster]

it's possible @Iceni's theory about the wiring being off is maybe happening.

normally with the gate mosfets i find it much easier to use the 2-wire setup (as in @Iceni's drawing) than try and muddle through the single wire setup, although bearing in mind the pic is the g&g v6 box rather than the cyma v3, but the same general idea just the contacts are in different locations.

 

[RostokMcSpoons]

I think I'd end up having to splice wires... basically I thought the simplified version with the single signal wire would be much easier to reverse (if I had to) than messing with the current wiring...
and in fact the instructions mention the second option when replacing all the current wiring with a heavier gauge.  

View attachment 84969

View attachment 123840

However... it's not working.  So I either reverse it and find a 7.4v battery that'll fit (having just requested an 11,1v nunchuck from Titan which won't fit, whereas the original 7.4v did, d'oh!) ... or I fix this.
I'm not entirely sure I'm brave enough to strip off what's there.

 

[Adolf Hamster]

personally, i'd go with the 2-wire setup.

iirc they give you plenty of wire with the 2 sets of connectors, enough to trim a length off to bridge the semi and auto connectors (if not, lemme know, mans probably has some lying around somewhere)

then run the heavy gauge direct from the mosfet to the motor (only place it's needed), basically the 2 motor spades going into the same deans plug which then goes to the mosfet.

 

[RostokMcSpoons]

They give you the connectors, and the two sets of signal wires (one single, one double) are both very long, but no heavy duty wire.
I could butcher some of my existing tamiya leads etc to harvest some.   

I don't have any spade connectors so I'd have to splice onto the rather short bit of red wire coming off the motor... which just feels like another potential point of failure, but I guess it's what I'm left with.

Ok. I have a plan of attack for tomorrow.  Now I'm off to the pub!

 

[Adolf Hamster]

the light wire is fine for the majority of the wiring going from the mosfet and across the 2 sets of contacts.

you'd only need enough heavy gauge wire to go from the motor to wherever the mosfet is going to be, for example the one terminal already going to the deans connector from the motor won't need touched, just trim the other wire coming from that deans and plug it straight into the motor.

something like this:

View attachment 84973

remove the green-traced wire entirely, cut the black striped wire where the green X is and solder it (black line) to the motor spade (or the the motor, if you feel so inclined)

your other 2 red wires you could leave as-is, personally i'd swap them for the light-gauge wire for the sake of neatness but that's up to you.

edit:

some top tier mspaint skills later:

View attachment 84974

so wiring wise:

1 has light wire going to the smaller mosfet connector, and to point 5 (which one doesn't matter)

2 has light wire going to the smaller mosfet connector and to point 6 (which one doesn't matter, as long as it's not connected to 1 or 5)

points 3&4 are wired with heavy wire to the mosfet deans connector (with polarity matched for the right motor direction), like the above pic.

 

[Iceni]

Dude it's the same as the AUG.

The single wire system only works when you have a single set of contacts, like a regular V2, V3 (AK). As soon as you have a secondary set of contacts the method I put above is the easiest way. 2 cut's and just run 2 separate loops.

It's actually on the same page as the V2 diagram, Under it... Figure 3 page 11 of the manual.


You don't need the motor spade connectors. Your putting a deans in and the motor is separate from the loom because of that. So provided you make sure you can get the motor out of the cage with the wires on (you can on an AUG, not sure about the F2000) then you can just solder the wires directly to the motor.
 

View attachment 84976

Those are pictures I did for another fet but it's the same diagram for the merf.

In addition to this you also have to put one of those single shot trigger back to normal.


Looking at how you've wired it I don't think you have put any power down the signal wire.

But it would only work in single shot, and full auto would cause the Mosfet to power down thinking it had a short circuit. So exactly what you saw. As the single shot trigger would initiate the motor, the full auto contact would be open, but there would be no signal wire signal as the COL would have broken the  semi contacts. So it would kind of fall over itself and go safe.

A single wire setup would look like this. Had to have a good think as to how it would work.
 

View attachment 84980

 

[RostokMcSpoons]

Ok, after a nice night in the pub and a good sleep, I'm back.

Thank you both for the diagrams...

I like to think that, self-deprecating humour aside, I'm a reasonably intelligent man, but I think I have a blind-spot for electricals and electronics, and so I'm going to ask for some step-by-step confirmation of what to do.  And in this case, quite literally, the blind-spot is what to do on the underside of the gearbox.

Do I need to clear both the trigger contacts, to fit the double signal wire?

View attachment 84988

Or do I re-connect one of the existing wires to the front connection, so it's back to how it used to be?

 

[Iceni]

1. Remove signal wire.

2. Move front trigger wire back to original position.

3. Cut the + and - wires as per this diagram.

4. make a decision - You can go with the double signal wire. Solder it to the green area wire tags. Preferred method. Polarity doesn't matter as this circuit is now isolated from the mains. The sensor wire can go any way into the Merf.

4.b. Go with a single wire as per the last diagram I posted above - note you will have to work out how to feed the + side of the trigger. Polarity is important. The feed from the + is essential and the sensor wire has an orientation on the Merf.

5. Connect the deans directly to the motor.

 

[RostokMcSpoons]

First step done...
View attachment 84990

Cutting the two wires below the tags now...  (this is the nearest I'll ever get to Mission Impossible...)

Do I just cut them as near to the tags as possible?  I did try to de-solder from the tags, but the solder just won't melt
 

View attachment 84991

So...

• The yellow crosses are cut
  
• The yellow lead is discarded
  
• The black/red is redirected to the motor (green)
  
• The signal wires (purple) are soldered to the tags
  

...?

 

[Iceni]

Yup cut on the yellow crosses.

Yellow tag wire can be discarded.

Deans directly to the motor with some wire, I often just solder directly to the motor with that gearbox as the cage can be removed with the wires on.

Purple to the signal wire.

 

[RostokMcSpoons]

View attachment 84996

 

[RostokMcSpoons]

View attachment 84999

Oh dear.

It does shoot, and doesn't stop like it did before.  

But single-shot still doesn't work correctly.  I sometimes I get single shots, but more often I get bursts of shots (and yes, I checked the settings to make it's set to single/auto)

Here's how it's set up now:
View attachment 113382

I can only try moving the signal wires to the front contacts, can't I?

(Edit: no, that's no different electrically than what I've got now)

Maybe I ask Gate tech support tomorrow

 

[Iceni]

before you do anything.

Pop a piece of tape over the plate on the trigger style contact... You may have just lifted the auto fire pins

With the tape in place you should just get semi.

Provided that works. the next step is to just lower one of the little contacts on the inside of the trigger/auto contacts until semi and auto are separate again.  Adjust only 1 pin.

View attachment 85003

 

[RostokMcSpoons]

Nope. 

It's odd.  I move the trigger gently and slowly back, I'll get one or two or three shots.   Yank it back and even with electrical tape or paper blocking the contact it'll run full-auto until I release the trigger

 

[Iceni]

If the tape isnt working then the problem is probably with the semi auto contacts. You might have nipped them up a little with the heat and it's holding the dolly.

You should be able to see the dolly resetting when you cycle the gearbox.

I need to head out for a bit - will be back in 1 hour ish.

 

[RostokMcSpoons]

View attachment 85005

In spite of appearances, the trigger contact isn't quite hitting the other one, so this was a successful single shot.

I presume your talking about the arrowed piece?

So yeah when it works I can see it push up.  When it doesn't the thing shuttles back and forth like a loom loon

Are you saying something's gone out askew on treadle?  This is a possibility.   Back when I was first trying to put this gearbox back together, I had terrible trouble with the plastic trunnion on the lower side of the gearbox, it'd slip from it's locating position on the gearbox and push the tappet plate up and out of position.  I tracked the problem down to a missing grub screw... not having one to hand I used a bent nail through the hole to hold it place... 

View attachment 85006 

I could take the gearbox apart to ensure it's still correctly located, but I'd expect it to bind altogether if it had moved out of position again.

But if you think it's worth a look, I will

 

[Iceni]

It shouldn't just push up. It should push up and snap back to the starting position without needing to reset the trigger. On semi auto.

So with the tape over the auto contacts -

A single full trigger pull -

Moves the dolly forwards - It touches the contacts.
COL hit's the dolly lifting it over the trigger - dolly snaps back - And it falls back into the reset position with no contacts been touched on some trigger designs it might stay at an angle but it should always snap back.

Trigger is released and lifts the dolly and picks up the step that will allow the trigger to be pulled again.


If the Mosfet is working on the program trigger, and is working in AUTO then the only fault that can be left is the Semi auto contacts and Dolly.

That whole assembly is the same as the AK. So getting a replacement is easy enough if need be. But I don't think this issue is the MOSFET if the program trigger is working as intended, as all that trigger is, is a push switch.