Mega Drive JAP Model 1 VA7 50/60 jap/eng MOD

I recently asked some help for modding a japan MD but this is another one, is the VA7 model and once again jumpers are in different position...

I got in the upper left side of the pcb this:

0 - 0 jp3
0 - 0 jp4

and in the lower right this:

jp2 jp1
0 - 0 0 - 0

remeberin the tip apolloboy gave me I watched the underside of the pcb to see which jumpers are connected and I found it for jp1 and jp2, as you can see




but cant figure it out about jp3 and jp4, here's a photo



unfortunately I don't have a multimeter to check gnd and +5v points...

I wonder also how is possible this MD give me colour in 60hz via composite without a crystal mod....is because of the cxa1145m chip?

many thanks as usual

 

Both those jumpers work on the same principle as any other model 1 Genesis/MD, you have two pads that are connected together and go to a pin on the VDP, and then two other pads that are connected to either 5V or ground.

JP3/4 is pretty easy to figure out, you'll notice that the two leftmost pads are connected vertically and those go to the VDP. The right pad on JP4 is 5V, which means that it's set to 60 Hz (it's a Japanese system after all). So for that end, all you need to do is cut the horizontal trace on JP4, connect the center pole of your switch to either one of the left pads, one pole to the right pad of JP3 (which as you can see is connected to ground), and the other pole to the right pad of JP4.

For JP1/2, it's essentially the same deal. The left pads of both JP1 and JP2 are connected to a pin on the VDP, the right pad of JP2 goes to 5V (which sets it to English) and the right pad of JP1 is ground (which sets it to Japanese). I'm sure you can figure it out from there.

 

thank you apolloboy you're my mega drive guru...tomorrow imma do the mod

dont you know how is possible I get colour in 60 hz via composite with this va7 model? I have another jap md (not va7) And I get color in 60 hz via composite cos it was modded with an oscillator for the asian pal market but this va7 has no mods at all

 

Could be your TV is properly detecting it as NTSC and hence why you get a color picture.

 

Because the Japanese Mega Drive does 60hz out of the box. Your other unit has the extra crystal (etc) added to "lock" the encoder (being Asian I would say 50hz) which will also allow 60hz as PAL60 (which most PAL tv's are happy to use).

Be aware that if that Japanese model 1 va7 uses the same ASIC (main chip) as the American Genesis, it will not like 50hz.

 

dealing with mega drives and thanks to you kind users I discover always new things about these machines...

the other jap machine I have is not an asian pal, it got the ntsc crystal in the middle of pcb and got the "av intelligent terminal" writings on the cover so I assume is a real jap one but have the rf mod and a little oscillator between pins 5 and 6 of the cxa

Really I don't know nothing about the va7 issue for 50hz, it has the 315-5487 chip in which I think audio is integrated as I cannot find any yamaha chip.

It will flickers or something like that in 50 hz? Hope is not a big problem, Imma do the 50/60 mod to give full compatibility, not for playing in shitty 50 hz.

update: through composite it gives me color on a new lcd and on multistandard sony trinitron, but b&w on my commodore 1084s. modded pal md's in composite give me b&w on all these 3 monitors.

 

I did the mod followin the apolloboy tips, everything went fine but like you suggest me, this crap va7 board dont like 50 hz at all...this, plus the shitty audio amp make this the worst model I have in my hands

 

Pop over to sega-16. You have 2 options for the audio fix. TmEEs crystal clear audio or the newer mega amp. Maybe worth a look?