Need response from a Castle tech for MMM question
 

I understand that my question will void the warranty, and I accept this. I've already modded mine so the warranty is void anyway.

With the failures of the Mamba Monster seemingly being attributed to the BEC circuit, is there a way to totally defeat the built-in BEC in favor of an external one? Just removing the red wire in the throttle cable only prevents the BEC from powering external devices (servos, Rx, etc), but still powers the internal circuits. And if the BEC goes bad, the ESC is dead. I know that you will eventually solve the problem and it will be as solid as the rest of your products, but in the meantime, I don't want to be forced to ship an ESC back and forth for repairs, not to mention the wait time in between.

What I want to do is open up the ESC, cut the trace at the input of the BEC circuit (effectively removing it from the circuit), and "inject" the voltage from an external BEC where the internal one's output is. Basically, turn it into an Opto ESC without true isolation from opto-coupling the throttle signal. FYI: I'll probaby be using the Koolflight UBEC, which is very stable and noise free.

I suspect you don't want such a method widely known, so I understand if you decline to answer. If I do not hear from you, I will start dissecting the circuit and figure it out on my own anyway, but was hoping to have a little help from the experts. :smile:

Thank you for your time.

I haven't heard of anyone's MMM dieing while running a external bec with the internal bec still connected, yet

I know, but I want to be SURE. :smile:

Brian, I dont think you have voided your warrantee by trimming the case. You only void it if you run without a fan. You dont need th top of the case to run a fan. I'd zip tie one on at least untill you are confident that the one you have isnt a dud. I know this would be very hard for the ulitmate hater of fanss to do, but to mee it seems prudent considering th situation.

Well, modded case or not, the mod to the BEC circuit will surely void it. And we'll see about the fan. If I can get a Quark to run cool passively, I think I can get the MMM to run just as cool if not better! But fan or no fan aside, I still want to make that BEC mod. Judging by reports, it will be a killer ESC if the BEC didn't fail.

At this point, NOTHING should void the warranty. People are trying to get the thing to work one way or the other. CC should seek feedback from the mod attempts and say "thanks."

Give Castle a call Monday morning. I called them yesterday about my MMMs and my need for a ESC by the 14th, and let's just say they went way beyond helpfull on coming up with something I can use until the MMMs are solid. Between what I've seen on the forums and what I got out of that phone call, I'd say Castle is willing to do whatever it takes to keep their customers happy. I'll bet they work with you on your idea to bypass the BEC. Their ph # is on their site.

My 2nd MMM just burned last night using the external ccbec, and the fan wired to the receiver. It ran good for a little while but once I got to the track and was warming up it went up in flames. :whistle:

If it went up in flames -- it wasn't a BEC failure. Most likely it was over current -- setup incorrect, and possibly demagged the motor. Every major failure like this that we have seen have been setup problems where the current rises from a damaged motor so quickly that the over-temp doesn't have a chance to kick in.

Patrick

So Patrick, how about the original question?

There's really no easy way to do it. You would need to remove multiple parts to isolate the circuits correctly. The input power to the BEC circuit comes from an internal plane with multiple vias and a poured copper plane on the top layer. There isn't any easy way to disconnect it.

You would need to remove the inductor, the switcher chip (MSOP-8) and the mosfets (the two TSOP-6 parts.)

Patrick

Mine burned. I put the Max back in and it is fine. Same motor, same connectors. The only difference is one is a MMM and one is a MM...and one works and one doesn't.

In that case, it could just have been a bad FET, it could have been a bad solder joint on a FET, or a solder joint could have cracked on a FET.

Send it in, we'll fix it up. :)

Patrick

OK, thanks for the response. I think I'm going to go this route just to ensure no BEC issues.

Patrick, to be totally clear, the components to remove are the ones in the pic below correct? This will completely disable the built-in BEC? I would;ve thought that just removing the coil would be enough...

http://scriptasylum.com/forumpics/mmm_bec_mod.jpg

I know I'll have to "inject" external 6v power into the MMM throttle power line so the internal circuits can have their power.

Those are the right parts. :yes:

BrianG, Patrick tell me that the internal BEC of the MMM have a 3.3 volts regulator to power the microprocessor of the MMM, so if you powered it with the 6 volts of your Koolflight UBEC, you risk to destroy your MMM:neutral:

Thanks Patrick!

David: No, I'll be injecting the 6v into the throttle lead back into the MMM, which is normally at ~6v anyway. The additional 3.3v regulator must be further back in the circuit.

Basically, I'll be using an external UBEC without pulling the red wire...

Success!

Removed the components Patrick suggested and it works like a champ. :smile:

http://scriptasylum.com/forumpics/mmm_bec_mod_done.jpg

The MMM switch is useless now, switching it off did nothing. So I bridged the contacts at the PCB (did this after the pic above).

And now, I can use the Castle Link without any mods, nor do I need batteries hooked up to the ESC. I don't know if this mod makes anything run longer or better, but I feel better with my V1. :smile:

So now basically it's an opto ESC?

Whoah nice one Brian.....I hope I am good with soldering iron as you are....

I see the fan plug went south too:lol:

Brian just created the first MMM lite...

$10 says it still conks out...


:lol:

Basically yes. Although, in most Opto ESCs, you still need the main battery connection as well.... at least that's how it is in the CC HV ESCs.

You'd laugh if you saw the iron I worked with. Since I knew those parts were destined for the trash, I heated one side of the IC while gently prying with a tiny screwdriver. The IC basically fell off when I heated the other side. I just cut the inductor out and then removed the leftover connections.

Of course! I wasn't using it anyway and it was added weight for nothing. :lol:


Let's see how long it lasts. I got this ESC really cheap, so if it blows, no biggie. It was more or less my experiment ESC. I've never blown an ESC yet, and I hope not to change that, so hopefully things will be good. The only things that can go wrong now is if the external UBEC fails (sending full B voltage to the internals - ouch!), or if the ESC simply decides to do a Schulze on me. :smile:

And neil, I have one thing to say to you: :tongue:

Impressive work Brian!

Can I nominate this to be a sticky ? BrianG is a legend. I have just done this mod to my dead V1 & magically, the esc has been resurrected.

http://i198.photobucket.com/albums/a...ing39/cc02.jpg
Before

http://i198.photobucket.com/albums/a...ing39/cc01.jpg
After

Regards,
Joe Ling

I hope this is applicable to V2......just in case mine dies ( I hope not too soon :lol: )...

Don't forget to remove the switch wires and bridge the solder pads where the switch goes. I did a little more testing with the switch in place and found that when it was off and ran it for a couple of minutes, I'd have odd performance. Something like cogging, but not. With the switch closed, everything runs perfectly. So, you might as well remove it and bridge the pads. Cleans up the wiring too.

Yep, curious me already tried that. Not good to have the switch opened.

Thanks.

Regards,
Joe Ling

Made up a little diagram showing the UBEC hookup. It's a little different than most setups since the output of the UBEC must be fed back into the ESC, but that's about it. Oh, and I used the ESC input power solder points for the UBEC input.

http://scriptasylum.com/forumpics/mmm_bec_mod_schem.jpg

Other mods done just for the record:

- Cut the case so the heatsink has better passive airflow

- To protect the circuits, I installed 1/8" thick foam pad strip along the motor and power wire solder points inside the case.

Sorry to be anal but any chance of rotating the pic 180 so that it lines up with the orginal series...

Ahh that feels better

http://scriptasylum.com/forumpics/mmm_bec_mod_done.jpg
http://www.rc-monster.com/forum/atta...5&d=1220038087

The lighting would be totally off, not to mention the little bin of fish-eye distortion there is would be off as well.

Just one thing from me, and then I'll shut up --

Make sure you don't leave any solder shorts -- good idea to use some wick and clean up the excess solder after removing the parts.

lol, no need to shut up. Without your assistance, I would have just removed the coil and possible done some damage. :smile:

After removing the parts, I cleaned the flux film off and made sure no traces were touching. Well there are a couple on the FETs that touch anyway, but I mean the others.

Keeps people on their toes. :smile:

I might do it sometime this evening if I get bored. Doesn't take long, just gotta flip the image, save, upload to server - that's a whole 3 minutes out of my life!

Have one minute back... ;) Ahhh that feels better - ;)

Also can use a multimeter to check adjacent pads to ensure there is no short. Of course got to realise that a couple of pads for the 2 smaller components are common.

If the eyes are failing, use a magnifying glass. Works wonders.

Regards,
Joe Ling

Ok I thought I got lucky after reviving my V1. Now my brand new V2 seems to be DOA. BEC output voltage less than 1V upon powering up. This is a long weekend in Malaysia & I really want to run both my buggy (V1) & new truggy (V2). Looks like I'm only going to achieve 1 out of 2. However, I am now bordering on adventurous & I'm thinking of pulling a surgery on the V2. V2 differs from V1 in that the DC/DC convertor is now a 10pin device. At least to my feeble understanding of electronics that's what it is. So, this is what I intend to do :

http://i198.photobucket.com/albums/a...ling39/XXX.jpg

I want to remove the parts marked with X's to achieve the same result as that of the V1's to remove the internal BEC & power the esc through and ecternal power source.

Now the 6million dollar question - will this work ? Are those the right parts to remove?

I understand the warranty will be void if I did it. How much do I have to pay if I found out the hard way that this idea does not work ?

Thanks in advance.

Regards,
Joe Ling