GUIDE: Telling apart good Genesis 1s and Genesis 2s from bad ones.

[Ace]

MK Number provides no indication of whether the console is good or not. All my Genesis Model 2s have model number MK-1631 except for my VA2.3 Genesis Model 2, whic has model number MK-1631A. So no, using the model number will not allow you to recognize good Genesis Model 2s apart from the bad ones.

[villahed94]

Great Update Ace! The bad audio of the Va2 MD2 is caused by its amp. It might require a CCAM MD1 ish mod in order to restore the PSG and of course clearer audio.The only thing is that you would get a higher quantization noise, due to the use of a YM2612 instead of the 3438.

[socram8888]

I see there are no info about PAL European Megadrives. I have three European PAL-G Megadrives and I can upload pictures from its insides and outsides

Also, if anyone wants to have a look to a audio comparision from a MD1 PAL V4 and a MD2 PAL V1.8, here it is:
http://goear.com/listen/bc632e4/star...d1-va4-unknown
http://goear.com/listen/b6da6b1/star...2-va18-unknown

[N.Saibot]

I see there are no info about PAL European Megadrives. I have three European PAL-G Megadrives and I can upload pictures from its insides and outsides

Also, if anyone wants to have a look to a audio comparision from a MD1 PAL V4 and a MD2 PAL V1.8, here it is:
http://goear.com/listen/bc632e4/star...d1-va4-unknown
http://goear.com/listen/b6da6b1/star...2-va18-unknown

The music is soo slow! Please, make a 60Hz switch for those consoles : P

[Ace]

Great Update Ace! The bad audio of the Va2 MD2 is caused by its amp. It might require a CCAM MD1 ish mod in order to restore the PSG and of course clearer audio.

I'm not so sure it's that simple. I once ran the raw PSG output from my VA2 Genesis Model 2 straight into my TV's audio inputs and the volume balance between the different PSG channels was just as bad as it is through Sega's stock audio circuit. In fact, running the PSG straight to the TV made the distortion in the louder PSG channels even worse. Chessage did post a mod for the VA2.3 Genesis Model 2 to fix the volume balance problems, though I haven't really put the mod to the test. I started on a VA2, but there are some things that don't match between the VA2 and VA2.3, so I'm going to make the VA2 stock again and try the mod on my VA2.3 to see if it improves not only the volume balance between PSG, FM Synthesis, Sega CD CDDA/ADPCM and 32X PWM, but also fixes the volume balance issues of the PSG.

The only thing is that you would get a higher quantization noise, due to the use of a YM2612 instead of the 3438.

Not quite. The YM3438 found in Sega ASICs is a modified version of the actual Yamaha YM3438 with a better DAC and many of the YM2612's bugs fixed. Let me quote what TmEE said about the YM3438 on the SpritesMind.net forums:

I have confirmed that MD2 uses an YM3438.

I got a bunch of Yamaha chips today and YM3438 were among them. I did some tests as I did on my MD2 and to my surprise everything matched Very Happy

downside of YM3438 is that it has very high impedance output that picks up lot of digital noise. Also the output is significantly louder than YM2612, and this all matches with MD2 output aswell.

So it would take a fair bit of work to get a YM3438 to work on a Genesis with a YM2612 due to the high-impedance output and overall louder audio output than the YM2612. And you would still have the same quantization noise and other bugs found on the YM2612.

I see there are no info about PAL European Megadrives. I have three European PAL-G Megadrives and I can upload pictures from its insides and outsides

Please do. Motherboard pictures are unnecessary, though. I just need a picture of the fully-assembled console taken from the same angle as my Genesis pictures. But if your third system is a duplicate MegaDrive Model 1 or MegaDrive II, don't take a picture of it.

[socram8888]

The music is soo slow! Please, make a 60Hz switch for those consoles : P

I'm planning to that switch one, but I still have to redesign the divider to get correct PAL video in color through the composite video output, as I don't like using RGB

Please do. Motherboard pictures are unnecessary, though. I just need a picture of the fully-assembled console taken from the same angle as my Genesis pictures. But if your third system is a duplicate MegaDrive Model 1 or MegaDrive II, don't take a picture of it.

The other one is a VA6 MD1. The full list is:
- MD1 PAL-G 1600-18 VA4 with CXA1145 and discrete YM2612, no TMSS
- MD1 PAL-G 1601 VA6 with CXA1145 and discrete YM2612, with TMSS
- MD2 PAL-G 1631 VA1.8 with MB3515 and ASIC-based FM synthesis, with TMSS

These have no FCC id, but you can still look at the stickers on the bottom: my VA4 non-TMSS dont have the "Protected by the following patents" text, but my VA6 TMSS do

[socram8888]

Here are the pictures from the VA4 non-TMSS Megadrive 1, with a CXA1145 video encoder:



Some things I've noticed:

• In the PCB next to the cartridge slot, there is a circle with a gold spot, next to the VDP ASIC. This is probably the best way to reconigse a VA4 motherboard
• No "Patents" info on the TÜV sticker
• The white part where the LED is placed (which is gone in my console as well as the 16-bit gold logo) is directly printed on the case
• There is an EXT port

And here is my VA6 TMSS Megadrive 1, with a CXA1145 as well:



Some things I've noticed:

• There is a wire on the motherboard named JP5. You can see it through the cartridge slot, so this is probably the best way to check if a board is VA5 or VA6
• There is some info about "Patents" on the TÜV sticker
• The white part where the LED is placed is a different piece than the rest of the case
• There is no EXT port. The board has the required connections to put one, so maybe there are some VA6 with an EXT port (probably not)

And a note: if your console has a "IC BD M5 PAL" board, the only way to know if yours is a VA5 or a VA6, is to look at IC4:

Consoles with that board and a 315-5402 ASIC are VA5
Consoles with that board and a 315-5433 ASIC are VA6

These consoles sound like: http://goear.com/listen/bc632e4/star...d1-va4-unknown

And about the rainbow effect on the CXA1145: I never noticed it, so probably either it's gone or it's too low

[Ace]

Perfect! I'll add those to the guide.

[socram8888]

Done

I've added some info as well

[Ace]

I do think something needs to be changed in the guide as I looked up the Fujitsu MB3514, and it actually does not have a DIP form factor. It's only available as a surface-mounted chip according to the datasheets, so there's no way it can be found on VA6 and older Model 1s.

EDIT: I would need to know what the Composite video looks like on each revision. Describe how clear/blurry, colorful/dull the picture is. I have no experience with using PAL out of a MegaDrive unless it's in black & white, so I'd like someone who's used a European MegaDrive to tell me how the Composite video looks like on a European MegaDrive.

Also, take a picture of your MegaDrive II.

[socram8888]

About the video quality, here's a screenshot I made with a USB video thing:
VA4:

Uploaded with ImageShack.us
VA6:

Uploaded with ImageShack.us
The sky looks different

Also these graphical glitches are not as noticeable as it may seem, as CRT has a high video persistance that hide them

EDIT: I can't make right now pictures of the MD2, as I'm fixing the cartridge slot and it's completely disassembled

[Ace]

Video capture won't do. I need you to describe exactly how you see the image on your TV. Also specify what TV you're using(it must be a CRT) and what are the brightness, contrast and color saturation settings.

[socram8888]

On my CRT, both look colourful, vivid and bright using the same configuration than for the DVB-T decoder (50% bright, %50 chroma, %80 contrast). They have that issue shown in the images, a small shadow of the images on the right (but much less, nearly invisible)

Also there is no rainbow on the image

[hacksquad]

Hi there, i just got few japanese mega drive, i'll post some pcb pictures of it.

My primary console, Japanese Mega Drive VA4 50/60hz mod




Japanese Mega drive VA6




Japanese Mega drive 2 VA1



I have problem with my Japanese VA6 mega drive 1, the left stereo headphone audio jack not working, even i followed the trace and check the sound out put on the IC there is no audio, just wonderin whether the amp IC issue.

Oh yeah the VA6 actually PAL mega drive, when i switch it to NTSC there was no colour, so i just changed 1 of the main OSC from 53.203 Mhz to 53.6931 Mhz , now i have colour.

[socram8888]

Where did you get that 53.6931 MHz oscillator?

I'm trying to give color to my Sega Megadrive PAL VA4 by manually dividing the master frequency by 12 using a 74F counter so I get the PAL color subcarrier. So when it's set at 50Hz, it outputs PAL-50, and when set at 60Hz it outputs PAL-60 (that's like NTSC but with a PAL color subcarrier)

I've searched for 4.43MHz oscillators too but no luck