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RC Car Repair

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Old 04-23-2010, 08:28 AM
  #1
nova20
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Default RC Car Repair

My parents recently gave me a box of my old toys that had been sitting in their attic... guess they wanted me to move it to my attic now that I've got one :-)

In any event, one of the greatest treasures I found in the box is an old 6V Tyco R/C Ricochet.

[youtube]http://www.youtube.com/watch?v=zvQPKZT92vU[/youtube]

I remember having more fun with this car than *any* other RC car I'd ever played with. Idrove that thing (as the commercial implies you should) like I hated it, and it would take it all and come back for more.... for about two months

Sadly, one day Idrove it through a puddle that was just a little too deep. It started going in circles, and before I could get to it to turn it off, The one wheel just stopped as if the motor had burned out. I must have put it in my room and forgotten about the whole ordeal.

Now it's 15 years later. I have a brand new 6V battery pack, and only one of the wheels will spin. I'm a bit of a tinkerer now, so I decided to take it apart and Ithink I found the problem. There's a green plastic rectangular part on the main board that has a brown circle on it, like someone burned it with a soldering iron. I imagine that in the time the tire was spinning full speed it got hot and melted.

I've come here to see if anyone has any suggestions. I don't know of anyone in my corner of the world (Americus, GA) that works on RC Cars, and I can't find any documentation about the circuitry (or even the car itself). All I can find are the original commercial and this forum. Can anyone help?
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Old 04-23-2010, 09:36 AM
  #2
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Default RE: RC Car Repair

Can you post a picture of the suspected burned part?  Maybe we can I.D. it.
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Old 04-23-2010, 09:39 AM
  #3
nova20
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Default RE: RC Car Repair

Sure. I didn't think to take pictures when I had it open, so I'll have to strip it down again. I'll have pictures in an hour or so (I'm at work now).
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Old 04-23-2010, 10:57 AM
  #4
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Default RE: RC Car Repair

full quality pics are here: http://picasaweb.google.com/nova20/RicochetProblem

Here's the back of the board (click for bigness):


In the lower right there are 4 sets of 3 connection points (right above the red wire). The problematic part is connected at the set of 3 in the upper left of those 4. It seems to be in line with the orange wire.

Wire layout:
white - battery
yellow - motor 1 (works)
green - motor 1 (works)
orange - motor 2 (bad)
blue - motor 2 (bad)
red - battery
purple - antenna

Here's a close-up of the part itself. Looks pretty nasty (click for bigness):


Camera was too close to focus on it, so here's a wider shot (click for bigness):


The text on the part:

NEC
B2772 Q
B772 Q
M 72
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Old 04-23-2010, 12:13 PM
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Default RE: RC Car Repair

It's a transistor. I've found some possible matches:

http://www.newark.com/stmicroelectro...tor/dp/38M2093
http://www.mouser.com/ProductDetail/...9LqplOmLibqLc3

Your part number threw me. After I looked at the pictures close up, I saw it was B772. You can put that in the search box on those sites and pull up the rest of the hits. Looking at the back of the board, the only thing Ican suggest there is to maybe resolder the green wire. That joint looks a little iffy.
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Old 04-23-2010, 01:49 PM
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Default RE: RC Car Repair

That older stuff had decent boards, that were actually repairable. Heck, they even indicate Emitter-Base-Collector locations. Just pay attention to that when replacing the part.
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Old 04-26-2010, 10:11 PM
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nova20
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Thanks! I don't know where that extra 2 came from (I corrected it in my post). I've ordered the part, and it looks like Ihave another excuse to practice my soldering skills.

Wish me luck! I'll let you guys know how it goes.
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Old 04-29-2010, 06:00 PM
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Default RE: RC Car Repair

Got the part in today and got all excited while I pulled out my soldering tools... desoldering braid, iron, and solder. Honestly I think I did a fairly good job, but sadly it didn't do the trick. The damned wheel just won't turn. I even took the part back out, turned it around, and put it back in. Nothing. It's possible I damaged the board with my 30W iron... but Idon't think so.

In any event, here's some pictures (as before, click for bigness)

New part in place:


On the other side, you can see my horrid soldering job. Actually, it's not that bad, there's just flux all over the place. How do I get rid of that stuff?


As you can see, I also re-soldered the green wire, but I think Imade it worse. However, that wire goes to the other motor (and works fine), so I'm not complaining.

Anyone got any more ideas? I'd restart from the ground up with all new parts, but I'd have to use the existing board (unless someone knows where I can get a new one).
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Old 04-29-2010, 06:26 PM
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Default RE: RC Car Repair

Holy crap, I had this truck. My mother got it for me as my last christmas present at home as a kid (17). I jumped that thing of the house and everything else I could and never broke a thing. Stopped running it do to the battery crapping out on me..
Wonder if it's in her attic??[&:]
Thanks for the 15 year flashback..
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Old 04-29-2010, 07:52 PM
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Has it really been 15 years since this thing came out?

Damn, I'm old. That was literally half my life ago.
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Old 08-18-2014, 01:37 AM
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I have a question how do i fix a ln old rc car it has some mud inside the chip and the two dynamos are nit working how do i fix that
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