Mod your Sega CD to use only one power adapter

Includes but not limited to: SNES, Genesis, Sega CD, PlayStation 1, Nintendo 64, Dreamcast, Game Gear and I guess the Virtual Boy.

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low_budget
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Mod your Sega CD to use only one power adapter

Post by low_budget » Sat Jun 19, 2010 5:20 pm

The angry video game nerd would be happy!

Disclaimer: I am not responsible for possible damage to your system. This requires careful soldering and cutting of pcb traces. It's not THAT hard, but you should have patience and experience soldering.

Apparently, Sega reserved some pins on the expansion connector meant to power accessories off the Genesis DC supply. This can be used to power the Genesis directly from the Sega CD. In the Genesis, the power in from the expansion connector bypasses the power switch. Applying 9-12v to Pin 28 (in the genesis) powers up the 7805 regulator after the power switch. An unmodified Genesis would be on whenever the power supply is plugged in. To turn the system on and off you have 2 options:
1. Connect a power switch between the input jack and pin 28 in the sega CD.
2. Modify the Genesis.
I will explain the Genesis modification in the next post.

Things you will need:

9-12v ac adapter that can deliver at least 2 amps
I used item # 16918 PS from http://www.mpja.com" onclick="window.open(this.href);return false;

22ga solid wire

soldering iron, desoldering pump, x-acto knife, Philips screwdriver

Modifying the Sega CD

1: Desolder and remove the filter shown. Lay the filter on its side and re-solder the output pins (bending them 90 degrees.)
2. Locate pins A28 and B28 on the expansion connector. Counting from pin 30 it goes: ground, audio, Vin. Solder a wire to both pins as shown.
3. Route this wire to the top of the board, near the power input jack. Make sure the RF shielding doesn't pinch the wire (or simply ditch the RF shielding.)
4. Solder the pin 28 wire to the connections shown in the wiring diagram.The power supply I used had the opposite polarity as the original (old PS had center pin negative,) so I switched the polarity as seen in the wiring diagram.
5. Solder a wire from power input jack negative to ground, and negative in on the filter.
6. Re-assemble Sega CD.
Last edited by low_budget on Tue Jun 29, 2010 1:06 pm, edited 2 times in total.

low_budget
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Re: Mod your Sega CD to use only one power adapter

Post by low_budget » Sat Jun 19, 2010 6:07 pm

This process explains the modification necessary to make the Genesis power switch operational with the modified Sega CD. This is for the Genesis 2, but the Genesis 1 procedure should be similar as it has the same connections. This mod will not affect normal operation of the Genesis. It can be unplugged from the SegaCD and used with the original AC adapter if you wish.

Note: do not use the Genesis power plug when the Genesis is connected to the modified Sega CD.

1. Carefully cut the A 28 trace shown with a sharp x-acto knife. Be careful not to cut any surrounding traces. I made a couple cuts so there's a small gap in the middle to ensure no connection.
2. Scrape off the green PCB coating near pin 28 to expose the copper.
3. Solder a wire to this connection and carefully route the wire so it doesn't connect to the RF shielding. It will connect to the power switch as shown.
4. When you're sure the power wire is properly routed, solder it to the input side of the power switch and use electrical tape to secure the wire.
5. You will need to trim some plastic off the plastic post under the power switch (on the bottom side of the case.) This needs to be done so the PCB can lay flat.
6. You will also need to bend down the RF shielding near the expansion port to prevent a possible short circuit.
7. You can now re-assemble the Genesis.

The power supply I used delivers 3.3A, so you could also power the 32x with no problems. If you wish to do that, you will need to install a output jack to the Sega CD and make or buy a connection cable. The 32x uses center pin positive polarity. The Sega CD and 32x are designed to receive power constantly, but only boot when the Genesis is switched on.

Now you have a Sega CD that doesn't use up a whole 6 outlet power strip. You'd think Sega would have thought of that!

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weaponepsilon
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Re: Mod your Sega CD to use only one power adapter

Post by weaponepsilon » Wed Jul 07, 2010 8:38 pm

SO you're saying that with these mods, one could power the genesis trio with only 1 adapter correct? I think you'd probably want a DC 12v 3.3 with a 5.5mm tip instead. I've horribly found out that Genesis systems need DC power.
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low_budget
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Re: Mod your Sega CD to use only one power adapter

Post by low_budget » Sat Jul 17, 2010 10:34 pm

I haven't tried powering a 32x with this setup yet, but hope to in the future. It should work fine. I will post a tutorial for that if I ever get around to it. One power cord for a 32x/sega CD setup would definitely make the system more convenient.

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Re: Mod your Sega CD to use only one power adapter

Post by duo_r » Sat Jun 25, 2011 9:13 am

Is this tutorial for Sega CD model 2 and Genesis 2? If so that is the same setup as mine.

Any effect to audio like noise or hum?

low_budget
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Re: Mod your Sega CD to use only one power adapter

Post by low_budget » Mon Jul 11, 2011 10:01 pm

I had great results with this mod. The only issue was sometimes the disc access light would stay on when I turned off the system. The genesis 2 has crappy audio to begin with, this didn't make it worse though. I also found a different mod on this page http://www.jamma-nation-x.com/jammax/genesismods.html" onclick="window.open(this.href);return false; (scroll down.) It powers the Sega CD from the Genesis instead of the Genesis off the Sega CD (my method.)
Since the Sega CD uses more amps than the Genesis, I think my method is better.
I used a 12v power supply, but it would be better with something like 9v (less heat.)

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