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Micro Magnum, Team Magnum, NSW
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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Another question is, now with no receiver and no spare ESCs, where can I get those parts quick?

Post Sat Aug 12, 2017 4:19 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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The wiring loom looks fine to me and that battery is good quality. I'll wait for Steve to confirm, but that damaged section looks related to the BEC. I wonder if something has shorted out the BEC at the Rx end? Was anything else plugged in to the Rx when this happened? Is it possible there is a short somewhere in the lead from the ESC to the Rx?
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Post Sat Aug 12, 2017 4:31 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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My current guess is, the previous ESC blew because of ripple current from the weapon ESC during testing. The drive ESC is closer to the weapon ESC than the battery, so it absorbed some damage.

What I found confusing was why is there a 16V cap on the drive ESC? (could it be the cap for the BEC module onboard?)

The Rx might have been damaged from the previous test as the earlier drive ESC's BEC was blown, I was ignorant to have thought that only the weapon ESC was damaged.

Post Sat Aug 12, 2017 4:33 pm 
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MoonSet416



Joined: 25 Sep 2016
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This is probably the part on the Rx that was broken.

Post Sat Aug 12, 2017 4:40 pm 
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Nick
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That could be possible. On the ESC, the control circuit runs at a low voltage; 3.3 or 5V so the 16V cap could be part of the BEC or smoothing for the micro controller. Current ripple is more likely to destroy the FETs rather than the BEC although anything is possible. I still prefer the shorted out BEC theory at the moment. Its a bit outside my experience, but current ripple is more likely to break something that is actually drawing current and not harm an ESC that is plugged in but not driving a motor.

That Rx damage looks like a large tantalum capacitor, which would be across the power rails.
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Post Sat Aug 12, 2017 4:43 pm 
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Nick
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Got to go out for a bit, keep posting if you find anything new.
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Post Sat Aug 12, 2017 4:44 pm 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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Thanks for the info Nick.

I just did some further testing without connecting to the Rx. Today's ESC seems to be able to work with no smoke coming out. However the previous ESC did not even twitch the motor.

Post Sat Aug 12, 2017 5:17 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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On the matter of buying a new receiver... I have a HK T6A V2 Tx, what kind of receiver is it compatible to?

Post Sat Aug 12, 2017 5:52 pm 
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Nick
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Can't you buy the same Rx you already have? https://hobbyking.com/en_us/hobby-king-2-4ghz-receiver-6ch-v2.html I think that's the one.
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Post Sat Aug 12, 2017 7:22 pm 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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The problem is that it probably won't arrive on time for the Nationals... Last time I ordered from HK it took like 2 weeks.

I found some on Ebay that will arrive quicker, I guess I will go with that.

Post Sat Aug 12, 2017 7:27 pm 
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Nick
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There seems to be stock in the local NSW warehouse - that usually arrives in 2 days if you choose the courier delivery option (which is cheaper anyway)
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Post Sat Aug 12, 2017 7:39 pm 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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Not really sure about that... When I bought my parts last time, I remember there were a batch of parts coming from the local warehouse, however they still took weeks to arrive for some reason and ended up in a weird news agency kilometers away from where I live.

Not that there's a problem with HK, but I kinda don't what to risk this one. This year's National is really special to me. Very Happy

Post Sat Aug 12, 2017 7:43 pm 
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Nick
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Another cause for the ESC and Rx to smoke like they did is if the battery + line somehow got shorted to the +5V BEC line. I don't see how that could have happened from your photo of the wiring but it does explain all the problems. It might be hard to prove that was the issue without test gear but check out all the soldering around the lead to the Rx at the ESC end.

Have you decided what to do about the weapon ESC? If you haven't ordered anything, I suggest getting an ESC with a higher voltage rating; 8 or 10S would be a good safety margin.

Another thing to do is shorten the wiring loom as much as possible. If there is any slack in the wires when they are in the bot, definitely cut out almost all of it.
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Post Sat Aug 12, 2017 9:48 pm 
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marto
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This shouldn't happen.........

I will replace ESCs but I wouldn't put em back in there without working out route cause.

Steve
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Post Sat Aug 12, 2017 9:56 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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Just had a look at today's ESC, on the surface I don't see how the + line can be shorted to the BEC line, but anything could happen in between the two boards, where I can't see.

Another thought, if the + line is shorted to the BEC line, wouldn't the 16V cap blow up because it's being powered from the other side?

Yeah a higher voltage ESC would probably hold up batter. Any recommendations?

Ah wire length... That's one of the design flaws: the ESCs have to sit in the conpartments beside the weapon, so the wires have to be that long... I will try to somehow solve this in a future version, but for now I can't do much about it as much as I wish to.

Post Sat Aug 12, 2017 10:36 pm 
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