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Post by Tom Maneiro on May 19, 2010 19:39:45 GMT -5
Well, i went ahead and swapped the big fugly heatsink on my Model 1. Checking on my unlimited parts box, i found four 78xx/TO-220 heatsinks from ancient 486/586 motherboards. I took a couple of them... ...and performed a trial run. The 7805 nearest to the video plugs does heat. A LOT. A simple heatsink won't work for it - it does generate lots and lots of heat! (if i were you, i would not put my finger there...). The second 7805 runs cooler, so a simple heatsink will do the job. After messing with some possible heatsink arrangements, i finished with this: For now, i'm doing a "burn-in" test with Vectorman If things do get too hot, i will try to put a fan there (not much space, so case modding will be a must on this one). Curiously, this is the only spot at the Model 1 that could overheat - all the remaining parts run very cool (including the 68K), at least at stock speeds. Maybe a higher-rated part (like a LM78T05?) would run cooler? IMHO, Sega seems to be pushing to the limit that poor 7805... UPDATE: 4 hours of Vector-Piece(tm) animation later, the Genesis has not asploded, melted, or even overheated. So the heatsinks are doing the job fairly well
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
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Post by oompa loompa on May 19, 2010 23:35:59 GMT -5
You don't need active cooling Higher rated part won't run cooler. Since this is a linear regulator, the heat that is burned off is from the difference between the input voltage and output voltage
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Post by TheMVRules on May 20, 2010 11:03:37 GMT -5
If Vectorman doesn't kill your console, Red Zone would do it.
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Post by Tom Maneiro on May 20, 2010 12:42:30 GMT -5
You don't need active cooling Higher rated part won't run cooler. Since this is a linear regulator, the heat that is burned off is from the difference between the input voltage and output voltage So you mean that actually, the stock 12V/1.1A AC adapter is to blame, and not the 7805 itself? Interesting... Now, this may sound stupid, but why the Model 1 requires 12V? Anyway, if my HD hasn't died after 3 years of running over 50°C, i doubt that my Genesis would die just for a bit of heat
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
Posts: 1,301
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Post by oompa loompa on May 20, 2010 13:02:41 GMT -5
You don't need active cooling Higher rated part won't run cooler. Since this is a linear regulator, the heat that is burned off is from the difference between the input voltage and output voltage So you mean that actually, the stock 12V/1.1A AC adapter is to blame, and not the 7805 itself? Interesting... Now, this may sound stupid, but why the Model 1 requires 12V? Anyway, if my HD hasn't died after 3 years of running over 50°C, i doubt that my Genesis would die just for a bit of heat I think 12V is used for the video encoder (that CXAxxxxx chip). The 7805 is never to blame , it's doing it's job . Your Genesis will not die from the heat. The 7805's have an internal thermal shutdown switch. The 7805 needs to be really really really hot for the thermal switch to trigger. I don't have any heatsink on the 7805, and I never had my genesis suddenly power off. It depends on what other peripherals you have hooked up too, so I'm probably just lucky Did you get my PM about the Game Genie? Probably way more than you can afford, but you could probably bargain (trade some of your 486 junk)
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Post by Tom Maneiro on May 20, 2010 13:11:13 GMT -5
Whoa, RARE! BsF.250 = around $35... not too expensive. I think that this is one of those "only once in life" gizmos Time to try to get some sales first - i already have lots of junk listed on MercadoLibre, but people is not buying junk these days. So i suppose that my dead HDs and that GG will stay listed there for a looooong while... *flees to the junkyard to sell those Pentium Pro's*
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Post by TheMVRules on May 20, 2010 13:32:28 GMT -5
Try some thing else than MercadoLibre.
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
Posts: 1,301
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Post by oompa loompa on May 20, 2010 14:05:20 GMT -5
Whoa, RARE! BsF.250 = around $35... not too expensive. I think that this is one of those "only once in life" gizmos Oh that's not too bad. I thought it converted to $70 . Cheaper than a flash cartridge (although you don't get 4mbyte of flash, you get 128kbyte VRAM+RAM using LAKABAJO )
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Post by Tom Maneiro on May 20, 2010 14:15:18 GMT -5
Try some thing else than MercadoLibre. We have very few options over here: - There is DeRemate, but it's the same thing (they're owned by ML, much like eBay "half.com") - There are other auction sites, but the stock is pretty much null (only BlackBerry cases, €xp€n$iv€ harddrives, autoparts and such crap - no rare items) - And noone use newspapers these days to sell used crap, except for cars, porn and spiritual services
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Post by GiGaBiTe on May 20, 2010 22:09:53 GMT -5
You can remove the black and yellow wires from the board, just don't touch the orange wire, some VDP signal goes through it.
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Post by Tom Maneiro on May 20, 2010 22:41:44 GMT -5
And what the heck does those cables there? Some last-minute Sega patch, or something else? I was tempted to kill them Good advice...
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Post by GiGaBiTe on May 21, 2010 17:47:39 GMT -5
They either ran out of room for traces or forgot to route that trace on that PCB revision and had to do it manually with a jumper wire. Just remember not to cut the orange wire unless you want stuff to not work.
If you can find the exact contacts on the bottom half of the board, you might want to remove the orange wire and put it under the board so you don't have to look at it all the time.
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Post by socram8888 on May 23, 2010 9:37:01 GMT -5
I think 12V is used for the video encoder (that CXAxxxxx chip) Why the MD2 has got no 12V power supply, then? Haven't nobody learned UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT B, A, START? Try it in my website: s4x8.tk/ ;D
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Post by Tom Maneiro on May 23, 2010 12:31:45 GMT -5
Haven't nobody learned UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT B, A, START? Try it in my website: s4x8.tk/ ;D Have you been smoking too much Google lately? Nice combo
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
Posts: 1,301
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Post by oompa loompa on May 23, 2010 13:50:28 GMT -5
And what the heck does those cables there? Some last-minute Sega patch, or something else? I was tempted to kill them Good advice... I don't know what those signals do (yes, they are signals, not power ), but I wouldn't remove them if I were you. If I were to guess, I'd guess that they're extra signals for the cartridge or expansion port I think 12V is used for the video encoder (that CXAxxxxx chip) Why the MD2 has got no 12V power supply, then? Doesn't the MD2 use a 12V power adapter as well? I was wrong anyways . You guys should check out the schematics for the Genesis . Everything on MD1 and MD2 is 5V. The 12V directly from the adapter gets routed to the expansion port If you have a 5V power supply, you could remove both regulators, and then directly connect VCC1 and VCC2 to the 5V source.
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