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Blown Sega MegaDrive Model 1 - How to fix it?


Daniël Oosterhuis

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A year ago, I wanted to fire up my Sega MegaDrive again. Being the idiot I was, I couldn't find the AC adapter, and I figured the SNES adapter would work. As you can guess, feeding AC into a device expecting DC isn't a great idea. Anyway, at the time I just put the MegaDrive away, and later learned what I did.

 

Anyway, today I was dusting off my consoles, as I was planning on selling some of them. Simply put, games have kind of lost my interest. I've gotten more into electronics and such, and games generally just don't hold my attention for very long, save for a few exceptions. However, I didn't want to sell my MegaDrive. Next to the interesting hardware it has, which I'm willing to experiment with once I get a bit better with electronics, the FM synthesis of the YM2612 chip just rocks. Even though a lot of Nintendo games have great music, nothing beats a good FM synth soundtrack. So, now knowing that I shouldn't use an adapter putting out AC, and that the Model 1 adapter is center negative, I went looking around for a suitable replacement. Eventually I got frustrated and just took a 12v 2A brick, opened the case, and took the soldering iron to it. All I did was swap the DC out wires, so instead of being center positive, it would be center negative. Hooked it up, the tip of the adapter fitted perfectly in the MD port, and... nothing. No LED, not a sign of life. At this point, I'm certain I blew it up.

 

I've heard that usually in such cases, the LM7805 voltage regulators are broken. Is this true? Could there be potentially more blown parts? How should I check for those?

I'm still a bit of a noob in electronics, but I'm not afraid to crack out the soldering iron and do readings with a multimeter, so throw it at me :-D

Edited by Daniël Oosterhuis
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I would check and see if there is a blown fuse somwhere near the power input. You could also check if power is getting to the voltage regulator with your multimeter. Pin 1 is the input voltage, pin 2 in the middle is ground, and pin 3 is the output +5v. Here's a link to the 7805 datasheet https://www.fairchildsemi.com/datasheets/LM/LM7805.pdf Also if you eventually get it working I would recommend replacing the voltage input capacitors.

Edited by electromaster_84
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I'll be damned. This evening I took it open to check the voltages. First, I checked the adapter hack I did. Yep, 12V DC center negative as expected. Connected it to the power and... a LED? The readings on the voltage meters were fine, 12V in, 5V out. Seems like it suddenly works again, although this time I had the metal cage off. Along the way, I reassembled it and kept checking. Right now, I have the entire plastic frame back together, expect for the main screws, and it still works. Don't know how, don't know why.

 

Anyways, I would like to recap the MD, do you know of any page or thread where I can find which specific capacitors should be replaced and which capacitors would be best to replace them with?

Edited by Daniël Oosterhuis
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You will have to look up which motherboard revision you have and go from there. I found some info, and one site that sell complete capacitor kits for NTSC systems.

 

Links

http://console5.com/store/kits/console-cap-kits.html?cat=120

http://console5.com/wiki/Genesis

http://www.sega-16.com/forum/showthread.php?10012-Genesis-Capacitor-List

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