Megadrive/Genesis 2 50/60Hz Switch

[BrokenFlight]

Surely this must have been asked before. I can't seem to find it when I do a search.

I've deon some searching on the internet and all I can find is this paragraph:

By Connecting Pin 107 of the 315-xxxx chip inside the Genesis 2 system to either Ground or +5v, you can select Japanese or North America as the system's territory. The same theory applies to pin 46 of the same chip: +5v is 60Hz and Ground is 50Hz

What I need is a picture of what to connect where.

Dummy alert:
I connected one wire to a contact that I think leads to pin 46, connected that to the middle of a three way switch, then connected the other two wires to JP3 and JP4. From what I gather, that should work, but it doesn't.

Luckily my Megadrive isn't fried. (yet)

As I said, I need pictures.

[Hammy]

find the pin on the chip. then take ground from around the edges of the board, +5v should be traced from after the transistors.

[InsaneDavid]

I believe on a Mega Drive 2 / Genesis 2 that has a JP3 and JP4 you need to connect the leads to the right hand side of each (looking at the front of the system). Not all Genesis 2 / Mega Drive 2 board revisions have the JP3 and JP4 points so I usually tie into points off the expansion port.

This thread about the best Mega Drive / Genesis converter has a lot of good information, including this...

Modding a Genesis 2 requires you trace a couple of pins from the 315-XXXX chip and isolate them. Pin 107 of this chip runs to a +5v plain for US and a GND plain for JPN. Basically you want to find where it meets up with the +5v plain and isolate it by cutting around it until it is isolated - don't just cut the trace as there's a VIA you can pick up the connection from that you want to leave in tact. Then you solder the center of a SPDT to the VIA or connecting point that runs to pin 107 of the 315-XXXX chip. One of the other pins on the switch gets connected to +5v (I usually get it from any connection found that meets up with A26 / B26 of the expansion port as that's +5v) for US mode, and the other pin goes to GND (again, A12, B12, A30 and B30 of the expansion port are GND but GNDs are easy to find) for JPN mode. 50Hz (PAL) / 60Hz (NTSC) is controlled by the same chip except pin 46 instead - GND for 50Hz and +5v for 60Hz. Procedure is pretty much the same. Sounds more complicated but I like modding Genesis 2 systems more. Remember if you're modding PAL Mega Drive systems you REALLY need to put in a 50Hz / 60Hz switch - world of difference.

Pins A26 and B26 (top and bottom) of the expansion port are +5v. Pins A12, B12, A30, and B30 are GND. There should be some nice big places to connect to them, usually on the leads from a capacitor.

Also make sure you break the original trace between pin 46 of the 315-XXXX chip and GND in your case (+5v in a Genesis).

[BrokenFlight]

I found this site but it's French. I managed to work from the pictures and I've successfully modded it.

The only trouble is my TV won't work with 60Hz unless it's with RGB cables. I don't suppose there's a way to get around that without doing an RGB mod, is there?

Edit:

I believe on a Mega Drive 2 / Genesis 2 that has a JP3 and JP4 you need to connect the leads to the right hand side of each (looking at the front of the system). Not all Genesis 2 / Mega Drive 2 board revisions have the JP3 and JP4 points so I usually tie into points off the expansion port.

I tried it connected to the right hand side of JP3 and JP4 before and it didn't work. It was probably because I didn't isolate pin 46, which I did having looked at the pictures.

[BrokenFlight]

I've got some pictures. I should have taken a picture of where I put the wires before I closed it up but I forgot to and now I can't be bothered opening it up again. Maybe later.

Somehow, I made a mess of the AV socket, so I removed it and soldered the RGB cable I made straight to the circuit board. It's not the best way of doing it but it works.

I put the switch on the left.


Here's what the RGB Ribbon cable looks like.


This is 60Hz.


And this is 50Hz RGB compared to RF. I took the RF picture on my unmodified Megadrive 1 because I obviously couldn't use RF on my newly modified MD2. :/ Comparing them that way, I didn't see much difference, but it's definitely clear when put side by side.



Thanks to www.mmmonkey.co.uk for the pictures and clear walkthrough. I used that site to make the RGB SCART cable.

[chaoticjelly]

If I was American, I'd call that cable "ghetto", but im not, so well done!

I'll laugh when it yanks out in a few weeks though, sorry, but I will

You have to have an RGB cable, because the 60hz is true NTSC picture, not "PAL-60" or anything like that, so the colour messes up on the RF because the RF module in the TV cant interpret the NTSC colour

[BrokenFlight]

I'll laugh when it yanks out in a few weeks though, sorry, but I will

And I'll slap my forehead saying "Durrr!"

The important thing is it works... for now. I'm trying to remove the AV socket from my broken Megadrive 2, but I couldn't do it cleanly with this one, so I'm not sure how I'll do it with the other one.

There's also the problem that I can't find anywhere that sells 9 pin din connectors.

[chaoticjelly]

If I was American, I'd call that cable "ghetto", but im not, so well done!

I'll laugh when it yanks out in a few weeks though, sorry, but I will

You have to have an RGB cable, because the 60hz is true NTSC picture, not "PAL-60" or anything like that, so the colour messes up on the RF because the RF module in the TV cant interpret the NTSC colour

[BrokenFlight]

I'll laugh when it yanks out in a few weeks though, sorry, but I will

And I'll slap my forehead saying "Durrr!"

The important thing is it works... for now. I'm trying to remove the AV socket from my broken Megadrive 2, but I couldn't do it cleanly with this one, so I'm not sure how I'll do it with the other one.

There's also the problem that I can't find anywhere that sells 9 pin din connectors.