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So I pruchased on ebay an Mega Drive I. The seller wrote in the auction that he wouldn't know whether it's working properly. When I got it I opened it up to have a look at the inside.
(Because I only have an AC adapter for MD II I could not power it up)



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I think someone did or tried a region mod, but without a switch, so a switchless mod?
I'm not quite sure, maybe you have an idea.

No region mod here. It is perfectly normal. During the course of building the systems little changes were made here and there. Rather than design and make new boards they used wires to change some things. If you notice, most, if not all, of the wires are going to labeled points on the board. I have the same situation on 2 or 3 of my Genesis model 1s.

JY

ok, but then I've got another question. The power LED doesn't seem to be connected to the MD. The top cover of the MD with the Power LED looks like this:



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Is there something missing?

Kyle wrote:ok, but then I've got another question. The power LED doesn't seem to be connected to the MD. The top cover of the MD with the Power LED looks like this:



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Is there something missing?

You probably broke it off when you opened the case. It's easily fixed, just solder it back onto the board.

If the power light doesn't come on once you solder it back, get out a Voltmeter and test the LM7805 power regulator. The legs should be ~11V, Ground, and 5V, in that order. Be careful when you do this, cause if you bridge the ground to the other legs you'll have to replace the regulator regardless.

If the 5V leg isn't reading 5V then the power regulator is blown and needs to be replaced. The LM7805 is a very venerable and common power regulator, easily found at Cellphone Shack, err Radio Shack. The Atari 5200 also uses an LM7805, thats how long this thing has been in use. Its easy to unscrew and replace this. I do believe the Model 1 has two LM7805s, so test both of them. If the 11V leg isn't reading correctly thats likely a power supply issue.

Seeing as you've whipped the LED off, now would be a good time to change the LED to a different colour.

The place that the LED is supposed to be connected to is labeled CN9 and is at the very bottom of the board where it is labeled M5 PAL. On all the ones that I have opened there have been a pair of wires running from that point to the white block that is on the LED leads.

JY

Jimmy Yakapucci wrote:The place that the LED is supposed to be connected to is labeled CN9 and is at the very bottom of the board where it is labeled M5 PAL. On all the ones that I have opened there have been a pair of wires running from that point to the white block that is on the LED leads.

JY

Right, someone else poked in this MD and ripped the cover off in a rush and messed up the connector. The wires were connected as JY noted to CN9. Those wires went to the white block still hanging on the LED Legs. When you open a model one you have to straighten the LED legs (which are normally bent out and back toward the underside of the lid) and slide the block off and remove the cover. Some idiot just ripped it loose. Since the legs look trimmed, you won't be able to use that to determine which is + and -. Slide off the white block, pop those tabs and you can pull out the LED. Use this picture to help determine which leg is which. Unless of course you put a different color in.



The blue and brown wires go to points labeled JP6 and JP7, so yeah, just looks like factory stuff. I am surprised the wires aren't tacked down with a blob of glue though.

that's factory except you're missing the 2 wires that connect the power led

the region mod connections are "jp1 jp2 jp3 jp4" near the right