WARNING! A new way for MMMs to fail including your precious V3!

[Ryu James]

Today when i was out bashing i went over a small jump and as i landed my Losi 8T Tekno conversion just died. I went over to it and sure enough it was my 5th MMM that had failed. I couldnt figure out what went wrong cuz i had just barely updated it with the most recent firmware.
After closer inspection i noticed that when i hit the bump my battery must have jolted forward just enough to bump the connectors on the ESC and push them into the heatsink. The result was two connectors touching the heatsink at the same time and....ZAP! Shorted out and fried my ESC. this is a major design flaw IMO with the MMM. Granted only the Losi 8 Tekno conversions are probably capable of this due to where the battery is mounted but when i looked at the MMM the connectors sit approx 1mm away from the heatsink. it doesnt take much force to move those connectors 1mm.
So i came up with a simple fix. i wrapped electrical tape around the connectors to keep there from being any connectivity should they touch the heatsink. anyway, just a heads up for all you losi 8 tekno owners with MMMs. i would make the change now and MMM owners in general it is something to consider.

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[DRIFT_BUGGY]

Damn, unlucky. Is everything else ok? (motor, battery etc.)

If they come stock with a fan, you'd think they could get away with a slightly smaller heatsink. At least one that doesn't come so close to the power connectors with a small plastic piece buffering that area between the two. Either that or do away with the connectors and have pre-soldered wires coming out.

[Ryu James]

i have now loaded in my first of 4 v3 MMMs i have, or rather the first that i have recieved out of 4 that Castle owes me. everything seems good. Neu motor seems good and batt is ok too. thankfully. i was looking at it again trying to ascertain exactly what happened and the best that i can come up with is just what i mentioned before. i can see the other connector that sits against the heatsink so all that had to happen was for one more connector (the wrong one) to touch up against it.
so i inspected my v3 before installing and that is the one i put the tape around. as you can see i did not put tape around the positve battery connnector like i did all the other connectors. the reason i didnt put tape around that one is because it rests against the heatsink and i couldnt get tape around it. however, as long as all the others are covered it wont matter. anyway, this is definitely an issue that Castle should look into.

The other possibility is that the male connector slipped out of the female connector and as it did managed to end up resting on top of the female and against the heatsink causing the short. in this scenario anyone could fall victim, not just Tekno losi 8 owners. either way, none of this would have happened if the heatsink were smaller and/or if one connector didnt already touch the heatsink and/or if the heatsink were generally better protected from the connectors.

[George16]

Just buy some 8mm heat shrink and use them instead of tape. It will work better.

[stum]

I'd be surprised if Castle covers this w/o a fee.. you obviously took the plastic cover off changing castles design and voiding the warranty. With the heat shrink that castle has on the motor output wires and the support the plastic case gives near the top it keeps this part from moving at all, I say the only design flaw is in your own changes from the looks of it. I guess we will see, but I've been running MMM's since the first batch of V1's and never had this issue, still have a v2 going strong in my erevo and 2 v3's in my 8ights (truck and buggy).

PS you may want to try a new mounting location in your 8t

[Unsullied_Spy]

Originally Posted by 1maxdude

If they come stock with a fan, you'd think they could get away with a slightly smaller heatsink. At least one that doesn't come so close to the power connectors with a small plastic piece buffering that area between the two. Either that or do away with the connectors and have pre-soldered wires coming out.

I'd prefer it to have a big heatsink assisted by a fan, the cooler the better. I've got an old passively-cooled CPU sitting here with a similar heatsink on it Stock they're pretty tough, but when you ram a battery into them (was the case even on it when it was damaged?) things tend to bend. I'd prefer wires soldered to the board like all their other ESCs, but they insist this design is better

[lutach]

Here's my situation now. What if one doesn't have the 1mm space between the plugs and the heatsink, what do you do then?

[Unsullied_Spy]

Originally Posted by lutach

Here's my situation now. What if one doesn't have the 1mm space between the plugs and the heatsink, what do you do then?

Take a pic and E-Mail it to Castle. They'll have you send the ESC back and they'll send you a fixed ESC or a replacement within a month or two.

[Tempted]

Originally Posted by Unsullied_Spy

I'd prefer wires soldered to the board like all their other ESCs, but they insist this design is better

The MMMs remind me of the first gen VXL systems that used the same design. It wasn't long before they updated it to wire leads with bullets. Castle should have learned from someone elses mistake.

[Unsullied_Spy]

Originally Posted by Tempted

The MMMs remind me of the first gen VXL systems that used the same design. It wasn't long before they updated it to wire leads with bullets. Castle should have learned from someone elses mistake.

My thoughts exactly. Patrick's response was that with the MMM's connectors being so much larger there was more solder holding it to the board so there wouldn't be a problem...I think if I end up buying one and it has bullets on the board I'll remove them in favor of wires.

[Jabe]

why dont they just replace those damn plugs with wires... it would have save many MMM's.
what do we benefit with those plugs, compared to wires?

[Unsullied_Spy]

Originally Posted by Jabe

why dont they just replace those damn plugs with wires... it would have save many MMM's.
what do we benefit with those plugs, compared to wires?

I'm not entirely sure...most motors you buy come with 1-2 inches of wire coming out the back so you have to make an extension to go from the ESC to the motor, makes no sense to me either. The CC Neu motors are supposed to have long motor wires so they'll plug right into the ESC but IMO it's a bad idea still.

[lutach]

Originally Posted by Unsullied_Spy

Take a pic and E-Mail it to Castle. They'll have you send the ESC back and they'll send you a fixed ESC or a replacement within a month or two.

They couldn't have missed them :

http://www.rc-monster.com/forum/showthread.php?t=15249

[Unsullied_Spy]

Originally Posted by lutach

They couldn't have missed them :

http://www.rc-monster.com/forum/showthread.php?t=15249

I remember reading that post, that was pretty stupid that it came like that. IDK how it passed QC unless they don't check their ESCs before shipping them.