发个老外的MD1 - DIY过程

勋勋 · 发表于 2010-10-17 16:55:34

本帖最后由 n805 于 2015-12-19 21:43 编辑

作者：大卫豪兰 David Howland
感谢：
Robivy64
Epicenter
evildragon
Nintendon't
Joe Redifer
MSXenix
Scias
目录
Introduction 简介
Hardware Note 硬件说明
Materials 材料
Case Mod 国防部为例
Disassembly 拆卸
Jack Holes 杰克孔
Blue LED 蓝色发光二极管
Stereo 立体声
Audio 音频
Composite 综合
Connections 连接
S-Video S -视频
Building the Amps 构建放大器
Connections 连接
Overclock 超频
Results 结果
Conclusion 结论
IntroductionThe Sega Genesis was a spectacular home video game console. In my opinion, it was king of the 16-bit era. Although it was more limited in its graphics compared to the SNES, it had a faster processor. In addition, the Genesis brought arcade action home in a way that I've never seen since. The games are just as spectacular today as they were in the 90's. Naturally, we want to continue to play the system, but a few updates to the hardware are necessary to fully enjoy the experience.
As the Genesis aged, later games that came out had to really push the boundaries of the hardware to reproduce the arcade experience and compete with other consoles. The result was games that require just a little more processing power than the Genesis could provide. In order to eliminate the slowdown that this caused, we are going to overclock the processor. Secondly, when the genesis was launched, the audio and video capability of most home setups was terrible. Most people connected their Genesis up using one of these.

These RF modulators totally suck. Video quality is blurry at BEST, and unwatchable at worst. Plus, there is no stereo sound. To remedy this, we are going to add rear RCA connections for stereo audio and a rear S-Video output jack.
Our goal is to improve the overall gaming experience by speeding things up and adding audio/video capabilities, all while maintaining an attractive outward appearance of the console. Hardware NoteThere were three different models of the Sega Genesis. This guide is only for working with the earliest (and best) model Genesis. The model 1 Genesis looks like this:

The Genesis 2 and Genesis 3 are progressively smaller and cheaper versions of the same system. Their internal composition is too dissimilar to be able to use the instructions I provide here. For instance, they use different output connectors, they lack the CXA1145 encoder chip, and they don't have headphone jacks. Now, this is not to say that you can't mod them at all, you just can't use this guide. In addition, if you open up your Genesis and it contains a Signetics CPU, or the main board doesn't look like the one in my photos, then you probably won't be able to overclock it. MaterialsWe'll be using the following.
I've included Digikey part numbers for all the parts that aren't available at RadioShack

Tools:: a" c0 Q1 x$ I. G
- Philips head screwdriver
- Soldering pen
- Drill with appropriate bits (1/4" and 9/16")
- Glue gun (optional)
- Wire cutter/stripper
- Needle-nose pliers
- Project knife
- Ruler
- Multimeter (optional)
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Parts:6 q! z- z4 V+ k
- 33 ohm resistor (2x) (Digikey: PPC33BCT-ND)
- 10k resistor (4x) (Digikey: PPC10KBCT-ND)
- 110k resistor (4x) (Digikey: PPCHJ110KCT-ND)
- 100uF electrolytic capacitor (2x) (Digikey: 565-1059-ND)
- 0.10uF capacitor (2x) (Digikey: 495-1071-1-ND)
- 9.216MHz TTL oscillator (Digikey: X113-ND)
- 2N3904 NPN transistor (2x) (Digikey: 2N3904D26ZCT-ND)
- 4-pin mini-DIN panel mount jack (Digikey: CP-2840-ND)
- panel mount RCA jack (also called phono plugs) (3x) (radioshack)
- project solder board (radioshack)
- 5mm blue LED (radioshack)
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Other Stuff:
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- Wire
- Masking tape
- Electrical tape
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勋勋 · 发表于 2010-10-17 16:55:40

本帖最后由 n805 于 2015-12-19 21:43 编辑

Case Mod
The first thing to do is to take this thing apart and add the necessary ports to the outside of case. In addition, I'm going to mod the LED. My main purpose for doing so is to change the outward appearance to signify that this is no ordinary Genesis, because this will be no ordinary Genesis when we are done here. The stock LED is red, so that leaves us with one obvious choice: Blue.

Disassembly
Take the top cover off by unscrewing the six screws on the bottom. When you take the cover off, it will be attached to the main board by LED wires. Bend out the LED leads and remove the wires from them.

Take note of which color goes with which pin. One of the pins will be longer than the other. This is the anode. On my Genesis this is the red wire. The metal piece over the main board is the RF shielding. It is supposed to prevent radio interference from emitting from the device. This is helpful for reducing interference with broadcast TV when the Genesis is on, but why would you be watching TV while the Genesis is on? As far as the operation of the console goes, it's actually quite useless.

Remove the shielding by unscrewing eight screws holding it down. Put it aside. We won't be using that part anymore. Its really not much use anyway.

To get the motherboard out of the case you will need to remove the screws holding down the cartridge connecter, the screw holding the front left corner down, three screws on the heat sink, and the bottom shielding clip. Be gentle pulling it out, and put the main board in a safe place.
Jack HolesWe
are going to add four ports to the outside of the case. Two RCA plugs for stereo audio, one composite video jack, and one S-Video jack. Why add composite video if we are going to have S-Video, you ask? Well, simply because to do so is very easy. To begin we cover the area we will be drilling with masking tape to protect it.

I taped up the inside, and used a ruler to measure out the holes. I have them about a half inch from the edge of the case, and spaced about 3/4 of an inch apart. My audio plugs are actually a bit closer together, maybe a half inch on those. Just make sure you have enough room.

Once they were marked, I used a hammer and nail to get the holes started. Its easier to aim the drill in the tight spot if you have a starter hole in the plastic to guide you. Get your drill. You will need a 1/4" bit for the RCA holes and a 9/16" bit for the S-Video hole. After drilling the holes, you will have something that looks like this. I wasn't very careful and mine came out a bit crooked. Oh well.

You make have to take a knife and carve out some space for the S-Video hole. Try mounting all the jacks once to make sure they all fit. If they don't, keep carving.

Blue LED
The LED in the model 1 Genesis is mounted permanently. In order to remove the old one we have to drill it out. Since drilling it out will require a hole bigger than the LED itself (which is 3mm), we need the next size larger LED. (5mm) If I'm going to mod the LED, I'm going to do it right. I bought the really bright 2600mcd lamp. As far as the voltage and current rating, you don't have to be very particular. The LED will light up as long as you're in the same ballpark.
I found a drill bit that was about the same size as the LED I bought and started drilling out the LED on the backside of the top cover. You will destroy the old LED while doing this. Just keep going, it's inevitable. Eventually you will be able to remove the old LED and clean up the hole.
Get the new LED and place it on the leads from the motherboard. Make sure to put the anode on the red side. Bend it up so it will fit in there good. When we put the case back together, we will place the LED in its new hole and use tape to secure it.

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勋勋 · 发表于 2010-10-17 16:55:43

本帖最后由 n805 于 2015-12-19 21:43 编辑

Stereo
Okay, so, the Genesis supports stereo sound. However, for some reason the only place stereo sound is found on the model 1 Genesis is at the headphone jack. Why did they do that? I have no idea, but we are going to place some nice RCA plugs on the back to carry that wonderful sound output. While we're at it, we'll add the composite signal too. If a TV doesn't support S-Video, it will at least support composite. Also, it uses the same kind of connector as the audio signals. I think it's worth the effort. AudioFirst, find the signals that drive the headphone jack. Look at the picture. The headphone jack is connected to the main board with a connector that is labeled 1,2 and 3.

Those pins are assigned to the signals as shown in the following table.

Pin	Signal
1	Gnd
2	R
3	L

Locate the contacts on the bottom side of the board and solder a good length of wire to them. Make the wire longer than you need. You can always cut away the extra. Be very careful. Don't use too much solder, you don't want to short circuit your pad to something else on the board. Try to make the wires lay flat against the board. Here is mine.

Composite
The Sega video output port on the back of the Genesis already contains composite video. If you look at the connector, you can see that some of the pins are labeled.

Make note of where the pin numbers are located and turn over the board. The following diagram explains each of the contacts.

Solder a wire to the composite pin as shown below.

Connections
Now that you have your wires attached to the board, you want to route them across the bottom of the board so that they don't interfere with anything. Make sure you avoid the area under the cartridge slot. Once you have them in place, tape them flat with electrical tape.

I bring my wires up next to the expansion port. There is generally enough space there to get them through to the top while still allowing the main board to lay flat in the case. Mount the jacks to the holes in the top cover and lay it next to the bottom as if you had flipped it open. Measure out just enough wire to reach the jacks when the case is opened, and trim off the rest. Solder the signals to the inside contact of the RCA audio jacks and wire the outsides to ground. They can share a ground. Notice that I actually brought the ground from the headphone jack. This isn't really necessary, since you can find a ground anywhere, but I wanted to bring it out in case I needed it to reduce audio noise. It turns out it wasn't necessary, so a ground lead from the top of the board may be a nicer choice.

Good show. It may be a good idea to test it before moving on. A continuity test with a multimeter is a good way to make sure the solder joints are good.

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勋勋 · 发表于 2010-10-17 16:55:52

本帖最后由 n805 于 2015-12-19 21:43 编辑

S-Video
Okay, the rest of that was kid stuff. Lets get down to business. As it was created, the Genesis only does composite video. S-video is a way to send video to your TV that differs from composite video in the way signals are transmitted. S-video breaks up parts of the signal into different streams that will help prevent them from interfering with each other. The result is a much clearer picture.
Building the Amps
Here is the schematic. Print it out. You're going to need it. We will be building two of them.

I assume that everyone knows how to read this and work with resistors and the like. I, for one, had forgotten the pinouts for a 2N3904 transistor. Here it is.

Also make sure to insert your electrolytic capacitors in the correct orientation. These parts only exhibit the behavior we want when current flows in the forward direction. (the negative side is the signal input) NOTE: Switching out the 33 ohm resistor for a different value with alter the brightness of the video signal. For instance, some people recommend using a 75 ohm resistor for the Chroma signal, instead of 33, which would make it slightly darker and less washed out. A smaller resistance would make it brighter. You can experiment with these values. I decided to build the amplifiers on a little project board.

First, I plan out where everything is going to go with a "dry run". Once I'm happy with where everything is I double check it. Then I triple check it, making sure that everything will connect and that my wires will fit.

Here it is, halfway done.

All the way done. Notice how I have Vdd and Gnd labeled.

This is what the back looks like...

From the side...

Now, I connect the long wires that will go out the Genesis. Ignore the oscillator (big metal rectangle) on there. We will cover that shortly. Now is another good time to go over all the connections with a continuity test.

Connections
With the circuit board finished, its time to hook it up to the system. NOTE: If you will be doing the overclock mod and want to put the oscillator on the circuit board, then complete that step before connecting the board up to the Genesis! We are going to just lay the circuit board on top of the Genesis' main board, so it is necessary to completely cover the bottom of the circuit board with electrical tape to properly insulate it. We don't want any contacts being made! Make sure no sharp points are sticking through.


Locate pins 15 and 16. Solder the input to your chroma amp to pin 15. Solder the input to your luminance amp to pin 16. This is probably the hardest part of the mod. Its tight quarters and you really don't want to short any of the pins. here is the result of my work.

Notice in the above photo that the two voltage regulators have pins that are numbered. Take note of these numbers. A table of the inputs and outputs of these parts is shown below.

Pin	Voltage
1	Vin
2	Vout
3	Gnd

Re-attach the heat sink to the voltage regulators with all four screws. After the heatsink is back on, take the power leads from the circuit board and connect them to one of the voltage regulators. Here is how I did it. It doesn't really matter where you connect ground to.

Here is the circuit board laying on top of the main board.

The outputs from the amplifiers then need to be connected to the S-Video jack on the top cover. This is the pinout for the female S-Video jack.

Pin	Signal
1	Gnd
2	Gnd
3	Y
4	C

Here is a picture of the connections again. Chroma is the red wire and luminance is the yellow. The S-Video cable has two grounds. You can connect them together. I bent the pins inward until they touched and soldered one wire to both of them. Once you have tested that everything is working, you can use a dab of hot glue to secure things in place. This is sometimes useful if you are afraid that something will come in contact with your solders or that a joint will break once you put the top cover back on.

Here is a picture of the whole thing.

Be careful putting the top cover back on. Make sure none of the wires get in the way of the cartridge slot. In order for me to get all those extra wires to fit, I had to cut out a bunch of the reinforcement structure on the inside of the case that goes above the expansion port (where the SegaCD would connect in).

Don't forget to tape the new LED in place when you close up the case. If you want to overclock, then continue reading before closing it up.

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勋勋 · 发表于 2010-10-17 16:56:08

本帖最后由 n805 于 2015-12-19 21:43 编辑

OverclockNow
for my favorite part. We are going to push the Genesis' CPU faster than it was ever intended to run. The stock CPU runs at 7.6 MHz, but people have shown that the good old Motorola 68000 can run significantly faster than that. Other modders have been able to get their systems running at 13 or even 20+ MHz. However, at these speeds the game starts to exhibit glitches. A special switch is also required to get the system to boot up when the processor is overclocked that much. I am overclocking mine from 7.6 MHz to 9.2 MHz. That is an increase of 20%, but low enough for the system to "just work" as normal. First, get the oscillator and find the dot on one of the corners. This diagram will show which pins do what.

Here it is wired up to my circuit board.

And here it is from the solder side.

Once the circuit board is installed in the Genesis, the clock must be supplied from the clk pin on the oscillator to the clk pin on the CPU. However, the CPU already has a clock. Therefore, we will have to disconnect the old clock first. In order to do so, I used the sharp point of a knife to "drill" through the tiny trace on the main board that carried the old clock. Press down with some force and slowly twist, and eventually it will be severed. Be VERY VERY careful not to destroy anything else on the board!!! Once you think you have severed the trace, try booting the genesis to make sure it will not do anything. Once you're sure you've severed it, solder on the lead carrying the new clock. The picture below shows both the new lead and the tiny hole I made to disconnect the old clock. Click for a larger view. The hole I cut is right next to the pin.

Results
Finally, we are done. Here is the finished product.

Okay, now is the moment of truth. Did our S-Video mod make a difference?
I tested with NBA Jam, a game that include lots of very small text. This is the before picture.

This is the after picture. Notice how the text has become readable.

Here is a close-up side-by-side.

I'd say that worked. Its too bad I can't show off the most important improvement over RF: The elimination of wavy lines and noise in the picture. The image is stable, crisp, and bright. Its much, MUCH nicer to look at. To test the overclock I like to use Lightening Force. Most of the lag from that game should be eliminated. Sonic the Hedgehog is also a good way to test the overclock. Collect a lot of rings and then get hurt by an enemy. That always causes lag on a normal Genesis. I have observed this to be nice and smooth after overclocking

Last, and probably least, here is the nice blue light at night. The powerful LED is casting a blue glow on the ceiling.

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勋勋 · 发表于 2010-10-17 18:11:14

本帖最后由 n805 于 2015-12-19 21:43 编辑

Conclusion
This is a great mod that works very well. The gaming experience is so much better with the better graphics and the reduced lag. Once you start playing this way, you can never go back.
The project was a success, but now that I've completed it, I have learned that I would want to do several things differently.
1) The wire I used was too thick. With all the wires connected to the jacks on the top cover, it was very difficult to get the case closed. Its a real rats nest in there, and I am still afraid that the pressure from the wires will be enough to bend a cap right of the main board.
2) By mounting the jacks high up on the back of the case, and soldering the wires on to them, they become permanent. I can no longer separate the top cover from the bottom. If I had to do it again, I'd probably try mounting the jacks right on the edge, leaving one side of the hole open, so I could slide them out if I felt like working on the Genesis again.
3) The 20% clock increase works well, but now I wish I hadn't been so conservative. If I did it again, I'd probably use a 10 MHz clock, for a 30% increase in speed. It is apparently just as stable as the 9 MHz mod.
Well, that's it. Its been fun. Good luck!
A big THANK YOU goes out to everyone who provided me with the information to do this project. They are listed at the top of this document. Most of the information here came from them in some shape or form.
本人英文也不是很好，所以没有翻译过来。资料不错。
英文不是很好的朋友用GOOGLE在线翻译一下，也可以了解差不多。

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SuperStar97 · 发表于 2011-1-12 20:29:48

本帖最后由 n805 于 2015-12-19 21:43 编辑

CPU超频这个牛

[url] ㈢㈢

勋勋 · 发表于 2011-1-15 10:28:18

本帖最后由 n805 于 2015-12-19 21:43 编辑

的确有点新奇，这还能超频。。。

[url] 亗亗亗亗

zikeyzuo · 发表于 2012-3-22 23:47:26

本帖最后由 n805 于 2015-12-19 21:43 编辑

很强的贴

[url] ё‐

ttntt · 发表于 2012-4-3 08:20:18

本帖最后由 n805 于 2015-12-19 21:43 编辑

这么个 diy啊我还以为自己做一台 md 呢

[url] ロロロロ

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发个老外的MD1 - DIY过程

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