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Best motherboard revision for Genesis sound
#1
I have a non-TMSS model 1 Genesis (which implies motherboard revisions up to VA5). Is there any difference between these in terms of sound quality? As far as I know, VA2 has a higher cut off frequency but distorts at loud volumes, while VA3 and above has a lower cut-off frequency but doesn't distort. Also, what are the chances for a bad capacitor and best way to check in the system? Thanks. Smile
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#2
http://www.sega-16.com/forum/showthread.php?7796-GUIDE-Telling-apart-good-Genesis-1s-and-Genesis-2s-from-bad-ones



this is the link you're looking for Smile
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#3
Thanks; I found the equipment post for the remasters that you put out awhile ago:



"The European Mega Drive Model 1, VA4, got replaced with a Japanese Mega Drive Model 1, V1. ... EDIT: actually Vref is ok, it seems that the signal is too strong when getting into the amplifier chip. Thanks to the guys over at sega-16!"

Found this thread as well: http://www.sega-16.com/forum/showthread.php?27397-VA2-Preamp-fix



There's so much conflicting information... can you tell exactly what you did for the mod?
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#4
Yeah, I made quite a mess on that thread because I tried to fix it another way and I failed. So a lot of confusion arose.



You can take for good what's written in the first post of the preamp fix thread.



Replace the 1000 pF caps with 4700 pF ones (or 5600 pF if you want the more rolled off sound of later revisions).



Replace the 47 KΩ resistors with 10KΩ ones.



You can look at the picture posted in that thread to find out where those are located.



Two recommendations, though.



Don't use ceramic caps in audio signals. Ever.

Use good quality polypropylene ones like Wima or similar.



Use carbon resistors and measure them with a multimeter to make sure they have both the same resistance otherwise you'll end up with a channel slightly louder than the other.
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#5
The only thing is that Joe (the OP in the thread) did the same thing but the volume was ridiculously low. Is there some other step? It's hard to tell from looking through that thread.



I don't have a multimeter so I guess I just have to trust that they're the resistance they say they are when I buy them...



Another random thing; I soldered on the NES to add resistor to enable expansion audio and it added a lot of buzzing/interference to the audio out that wasn't there before... if that happens after I solder with the Genesis I'm screwed. I'm not experienced with soldering at all.



edit:

These caps have your approval? Smile http://www.ebay.com/itm/10-WIMA-0047uF-4700pF-63V-volts-2-5-polypropylene-film-pulse-capacitors-/290617645681?pt=LH_DefaultDomain_0&hash=item43aa295a71
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#6
If you're not experienced with soldering then I STRONGLY recommend you let someone else do these mods. You have to remove SMD components on the Genesis and put through hole stuff on the pads which are VERY fragile. If the pad goes off, you're basically screwed.



Wima are among the best caps for audio, you can't go wrong with them.



For power supply caps I always use Panasonic FM (or FC)

For audio signals, if an electrolytic cap si needed, go with Elna Silmic II, other wise WIMA for polypropylene.



And yes, now that I remember, there was another resistance to change to get the volume back to normal levels.

I wrote that I use a 18KΩ resistor but can't remember where :|

I'm pretty sure it's near the volume trimmer, but can't remember which resistor was...
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#7
Sorry to keep asking questions over and over like this; you don't happen to know anyone I can send this to to perform the mod, do you?



Currently getting the parts that are necessary shipped to me ATM (the Wima caps, the VA2 Genesis, etc.) Won't get excited just yet though until after everything is said and done with no issues. I'm pessimistic SOMETHING is going to go wrong, haha.



-

edit: I think I figured out where the 18k resistor goes: http://postimg.org/image/yezyp0l2b/

and this post says: http://www.sega-16.com/forum/showthread.php?27397-VA2-Preamp-fix&p=661697&viewfull=1#post661697



So basically leave the 10k resistor as is, and replace the 33k with a 18k. Sweet; glad that's settled.
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#8
Yup, that's the one!



I'm also always pessimistic. From experience, there will ALWAYS be something that will go wrong, no matter what. Tongue

The point is if it can be fixed or if it cannot. If it can be fixed then it's no big deal but if you can't revert the damage... well, that sucks.



Where are you from? I could do the mod for you at no charge other than shipping but I'm afraid that shipping will be quite expensive.

I'm pretty sure you could send it to any repair center and tell them exactly what to do and they'll do it for a very low price.
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#9
I'm in the USA in VA. I take it you're somewhere in Europe (Italy)?
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#10
Yup, I'm in Italy, that would definitely be too expensive I'm afraid.
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