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PostPosted: Sat Jun 03, 2017 10:45 pm 
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You're probably wondering how I managed to do something like this, but I want to give some background so I don't feel like a total idiot. :lol: (This actually happened over two weeks ago, but I couldn't post then and forgot about it until now.) In my "honor's" physics class at my high school, our last assignment was a Rube Goldberg machine that had a bunch of aesthetic requirements, (don't know why; not even related to physics) including having a "theme" (we chose Tetris; barely any artwork) and having to make a sound at some point (I figured I would get music from the Gameboy game). Everyone was struggling to figure out how to make a noise with anything, but I knew I could have two wires going to the back of the Gameboy in the battery compartment for one battery and have one other wire going to each contact for the other battery and have the Gameboy on and the volume up, to where I could make it turn on remotely. (A lot of people ended up using birthday cards; I over-engineer everything...) I did that, and it worked fine; however, my teacher wanted it to get to the title screen music and not just the jingle, which meant I had to put it toward the beginning of the machine for it to play in time, and with how late in the project it was, I ended up having it share power with a motor, which worked perfectly fine. However, We later needed another motor, and that also worked fine, but we only got to test it twice before a member of my group took it home with him (and must have screwed up the sensitive wiring when he continued working on it). The next day, the sound was supposed to work, but when we tried to show it to the teacher, the Gameboy miraculously wouldn't turn on, which she said was because it "wasn't getting enough power". She told us two use two more AAs in a series and it would work, which I knew right away was a very shitty idea but class was ending and we would have gotten a failing grade, so I tried it, and it must have been enough electricity to jump the loose connection I later found because the translucent purple Gameboy Color turned orange in the battery compartment. :shock: Obviously, I unhooked it a millisecond after it happened, but it already smelt like burnt ass and knew it was probably dead, which it was. Surprisingly, there is no obvious damage visible and the game inside (Tetris) actually still works, which is why I wonder how extensive the damage is. (This should be apparent to you people, but I really don't know anything about electricity... At least I have four other Gameboy Colors. :lol:)


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PostPosted: Sun Jun 04, 2017 3:11 am 
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I don't think it's hopeless, but I can't say for sure. I don't know the GBC hardware at all, but battery-powered electronics (beyond the simplest cheap stuff) often would have a regulator in there. If the power supply isn't built out of custom parts, you could replace those if the damage was limited to those parts. I doubt the CPU etc. was directly connected to the battery.

I'm definitely a newbie when it comes to magnetics (I'm just now for the first time building a circuit that uses some inductors), but my uh-oh moment when reading that post was when you said the GBC was sharing the power supply with a motor. I know just enough to be a little dangerous, but what I do know is that a motor running backwards is a generator. And that powering an electromagnet will build up a magnetic field. When you remove the power, that magnetic field will collapse, and that power will have to go somewhere. That should be directed somewhere safe with a diode (look up "back-emf diode" or something). If there was no protection, the GBC power supply was probably not very happy to see this.


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PostPosted: Sun Jun 04, 2017 5:24 am 
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Back EMF is a serious problem, controlling a relay or motor without a protection diode is asking for trouble, the pulses reach tens or even hundreds of volts, depending on the inductance of part in question.

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PostPosted: Sun Jun 04, 2017 1:10 pm 
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Memblers wrote:
my uh-oh moment when reading that post was when you said the GBC was sharing the power supply with a motor. I know just enough to be a little dangerous, but what I do know is that a motor running backwards is a generator. And that powering an electromagnet will build up a magnetic field. When you remove the power, that magnetic field will collapse, and that power will have to go somewhere. That should be directed somewhere safe with a diode (look up "back-emf diode" or something). If there was no protection, the GBC power supply was probably not very happy to see this.

Sharing it with two 3V motors... :lol: The motors were under little load, (one rotated a couple of popsicle sticks holding a marble, and the other wound up a string that pulled a small cardboard sign up like a draw bridge; both turn themselves off by hitting another switch) but I don't know if even something like that is enough to cause damage. I forgot to mention that I actually used another Gameboy Color here, (after destroying the other; it was really hard to force myself to, but I didn't really have any alternative at that point...) and it worked with the two AAs. As I said earlier, the problem was a connection in the wires; I stripped two wires and wrapped the ends around each other the best I could before wrapping electrical tape over it, but I found the connection was broken later, with the wires close enough that it worked sometimes.

Thanks for the information though. :) I know some people who might be able to better figure out what's wrong with it, but I know that I first need to actually open the thing first. The Gameboy Color, like the other Gameboys, uses these annoying tri-wing screws (probably so people can't easily open it), and I don't have a screwdriver for this. Hopefully Lowes has some, but if not, I'll get one off eBay.


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PostPosted: Sun Jun 04, 2017 2:03 pm 
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Espozo wrote:
The Gameboy Color, like the other Gameboys, uses these annoying tri-wing screws (probably so people can't easily open it)

A suitably sized flat-head precision screwdriver from the dollar store fits into two of the three wings of Game Boy and Nintendo DS tri-wing screw heads. Want a photo?


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PostPosted: Sun Jun 04, 2017 2:25 pm 
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Yes.


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PostPosted: Sun Jun 04, 2017 2:41 pm 
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A while ago you could find really cheap replacement GBC cases on eBay that came with tri-wing screwdrivers.


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PostPosted: Sun Jun 04, 2017 3:41 pm 
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Somebody asked for pictures.


Attachments:
this_screwdriver.jpg
this_screwdriver.jpg [ 64.65 KiB | Viewed 964 times ]
turns_this_screw.jpg
turns_this_screw.jpg [ 45.6 KiB | Viewed 964 times ]
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PostPosted: Sun Jun 04, 2017 8:05 pm 
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I thought I had a screwdriver that small, but I couldn't find it. I'm going to get some stuff from eBay anyway, so I'll just buy a tri-wing screwdriver.


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PostPosted: Wed Jun 14, 2017 4:48 pm 
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Didn't take to long to figure out what failed. :lol:

Attachment:
Inside Gameboy Color.png
Inside Gameboy Color.png [ 1.8 MiB | Viewed 800 times ]

It appears to say "D2+" on the right side, and "3-" on the left.


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PostPosted: Wed Jun 14, 2017 4:53 pm 
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You blew up a diode. ("D"2)

It might be a zener diode ... ordinary (i.e. "not zener") diodes aren't usually what eats it when something is overvoltaged.

(Hunts down a schematic) Oh. That's a reverse-polarity protection diode instead. Part # is "1SS355".


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PostPosted: Wed Jun 14, 2017 5:11 pm 
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Thanks a lot. :) It looks like I can purchase one from here: https://www.digikey.com/product-detail/ ... ND/3774962


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PostPosted: Wed Jun 14, 2017 5:15 pm 
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Random caveats:
#1- you'll pay a significant overhead for shipping if you get it from digikey. (try comparison shopping using octopart and/or findchips)
#2 - do you have access to the right soldering equipment?
#3 - something else may have broken also. Try just desoldering the diode altogether and see if it works before you invest in a replacement.


Last edited by lidnariq on Wed Jun 14, 2017 5:19 pm, edited 1 time in total.

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PostPosted: Wed Jun 14, 2017 5:17 pm 
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lidnariq wrote:
do you have access to the right soldering equipment?

Yes.

lidnariq wrote:
something else may have broken also. Try just desoldering the diode altogether and see if it works before you invest in a replacement.

How should I connect both ends in the meantime?


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PostPosted: Wed Jun 14, 2017 5:24 pm 
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The diode is there to protect later parts from negative voltages—if you don't connect a negative voltage it shouldn't matter. (Normally the diode shouldn't conduct, so a missing diode will never conduct) Obviously you want to put it later, but for (careful!) testing it's ok.

If you'd used the external DC power jack, the fuse F2 would have blown instead of the diode. But for some reason, the battery contacts are unfused against reverse polarity.

Hopefully the fuse F1 will have protected the DC/DC (boost) converter U5, but...


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