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

[Ace]

The preamp appears to be the issue which has excessive gain as Villahed mentioned. The fix here, unless there's something else that needs to be done, is to change two resistors and capacitors used on the preamp. The resistors are 47Kohms and the capacitors are 1000pF. Those parts are 10Kohms and 5600pF capacitors on VA3 to VA6.8 boards, but this results in slightly heavier low-pass filtering, so if you want to lower the gain of the preamp and keep the lighter low-pass filtering of the VA0 MegaDrive Model 1 motherboard, replace the 47Kohm resistors by 10Kohm resistors and replace the 1000pF caps by 4700pF caps.

[parafin]

Thank You. Ace! I try to locate this parts but did not find. I am not strong on schematic MD. On top there is no this parts. Back side is only small SMD parts, I need to know closer where I must search. Its near Yamaha chip or sony? Friends please help me. If You need photo just ask part of board and I shoot...

[villahed94]

It's close to the Sony chip. Please take good pics of that area.

[parafin]

Ok

[MaxWar]

Is it just me or that motherboard is like.. Ultra clean? Whenever I open up a genesis console the thing is usually filled with dust balls.

[parafin]

Is it just me or that motherboard is like.. Ultra clean? Whenever I open up a genesis console the thing is usually filled with dust balls.

First thing what I do when buy old console - open and clean...

[Ace]

Okay, Parafin, refer to the edited image I attached to this post for the preamp gain fix.

Circled in red are the 1000pF capacitors used to low-pass filter the audio. These need to be replaced by 4700pF capacitors.

Circled in blue are the 47Kohm resistors. These need to be replaced by 10Kohm resistors.

[MaxWar]

First thing what I do when buy old console - open and clean...

Well, Ill usually spray some canned air to remove the worst but this thing looks like you put it in the dishwasher

[parafin]

Ace You Are great! Thanks. Later I tell result.

Well, Ill usually spray some canned air to remove the worst but this thing looks like you put it in the dishwasher

All You need is love and Isopropyl alcohol

[parafin]

It work. But still have sizzle sound on low volume. Is possible improve it?

[ApolloBoy]

It work. But still have sizzle sound on low volume. Is possible improve it?

You need to recap it. I have an early Japanese Mega Drive as well and it had sound issues when I first bought it. I've since recapped it and it sounds great now.

[parafin]

You need to recap it. I have an early Japanese Mega Drive as well and it had sound issues when I first bought it. I've since recapped it and it sounds great now.

You mean replace Electrolytic capacitor?

[MaxWar]

You mean replace Electrolytic capacitor?

correct.

[Bottino]

Ace, i want to congratulate you for this amazing guide. It was extremely useful for me, thank you.

Thanks to your guide, i bought a couple of days ago a HDG Genesis in amazing condition. It doesn't have TMSS ( not sure what the revision is yet) and has some rainbow banding but thats easily ignored
It looks great, plays great and you were right about the sound, its phenomenal. Especially compared with my old Tec Toy Va0 Mega Drive III( Genesis 2 for you guys)

[redsox2013]

So, all this time I thought I had a VA 2.3 model 2. The cartridge slot is exactly the same one as in the picture on page 1 for the VA 2.3 (with the two rows of squares). There's no mistaking it either - it doesn't resemble any of the other cartridge slot pictures at all. I finally opened it up, and it's a VA1, with a Samsung KA2195D video encoder, made in China. I've never experienced any of the issued that are supposedly associated with these "bad" model 2's. The picture has always seemed clear and bright, and there's no rainbow banding. I play all of my games through a 32X, so maybe that helps in the video department.

As far as sound goes, it's always seemed good to me, but I don't have another system for comparison. It's always been hooked up to a 10+ year old CRT TV via AV. I've never connected it to a real sound system, so maybe that's why any flaws haven't really been noticeable to me.

I'm kind of bummed because I thought I had one of the best models, so now I'm going to try to track down a VA 2.3 or 4 with a Sony CXA1645 video encoder, and the sound chips that are supposedly close to Model 1 HDG standards. Unfortunately, now that I can't identify one by looking at the cartridge slot, it's going to be tough.

There are a few retro stores in my area that sell Genesis consoles, but they obviously won't let me take them apart.