50/60 Hz mod on a Model 1 U.S. Genesis - ?'s On The Clock

[Lastcallhall]

I'm working with another forum member on modding a model 1 for 50/60 Hz, and I had a question asked of me that I'm not entirely sure of the answer. After I wire up JP3 and JP4 to a switch, I know I'll need to build a circuit for s-video and composite out to get a proper picture. I'm using the mod shown here: http://zipplet.co.uk/index.php/conte...ronics_mdpal60

And it says to use a PAL clock (4.433619MHz) to generate the proper signal. My prospective buyer asked me:

I've read the link you gave me regarding this PAL mod for S-Video and Composite. One thing concerns me though. Does that mean when the mod is fulfilled that RGB out has also PAL output with a slightly lower master clock? If this is the case i'll abstain because the slower master clock means lower pitched sound like on a PAL Megadrive. I want to avoid this at all costs, the higher pitched sound was the reason to buy a Genesis for me. Enlight me please.

I don't have the answer to this, and I was hoping someone might help, as he plans to use the machine for mostly RGB out, with the occasional s-video/composite session. Thanks!

[Robivy64]

You should be OK. If you were replacing the master clock (53.693xxMHz) for NTSC consoles with one of a lower value, then you would have the lower-pitched sound, etc.

This is just a modification to the color burst frequency (3.57MHz for NTSC IIRC).

[Lastcallhall]

Thanks for the help!

[cheaterdragon1]

I have a question regarding the 50/60 hz mod. If your console is a 60 hz console and your modding for 50 hz, you want the 3.579545MHZ crystal. And if it's the other way around than you want the 4.433619MHz crystal. Is this correct? Also besides the crystal differences, is the mod is the exact same for people who originally had 60 hz, and people who originally had 50 hz?

[omp]

I have modified both Mega Drive and Genesis (model 1) and I used the 4.43(etc)Mhz crystal, it worked for both. As long as you lock the video frequency to the video encoder (which the mod effectively does by separating it from the console), you should be fine. Though I am in Australia (PAL land) so that is why I used 4.43...Mhz.

I recently modified a nomad with 50/60 + region switch (combined single switch mod) and I used a 4.43....Mhz oscillator to lock the frequency, it was really quite easy (dare I say easier than doing it to a model 1 as there is no circuit to make).

*edit* The mod is effectively the same but you need to pay attention to the spec sheet, for example when I did the nomad, pin 6 (on the video encoder) is the clock/frequency signal, pin 7 is either sent to ground (PAL) OR has +5v (NTSC). It is important you match the frequency to the state of the chip (PAL/NTSC).

[Lastcallhall]

So, I'm finally getting around to this, and I have a couple of concerns.

First, I've already cut the trace on JP4 and soldered wires to both sides of the trace, and one onto the far side of JP3 to a SPDT switch. I haven't tested it yet, but that part is so easy, I'm sure it'll work.

Now, after reading through the link above, what I'm getting from the tutorial is that by doing this mod, you effectively kill any NTSC signal due to permanently grounding pin 7. This is not acceptable for what I wish to accomplish, which is a unit that will toggle between US and JP regions, as well as 50 Hz and 60 Hz modes, as well. since I already have the 50/60 Hz mod wired to a SPDT switch, would it be possible to add yet another switch, probably a DPDT, to swap between crystal frequencies and voltage/ground to be used in conjunction with the 50/60 switch? That would mean cutting pins 5 and 6, wiring the PAL circuit and ground to one side of the switch, and using the solder pads on pins 5 and 6, along with a 5v source for NTSC on the other, with pin 7 as the common point...

Right?

[omp]

You could yes, that is how it is done (on a model 2) here http://www.damomonster.com/Mod_Pages...gaDriveM2.html.

But you would need the circuit as shown for a model 1. The downside is you *could* introduce video noise as you would need to make the wires to long.

There is nought wrong with "locking" the frequency, I have done it more than a dozen times with absolutely no issue. If you want to lock it into NTSC I believe (and maybe wrong) you would the 3.57(something something)Mhz crystal and instead of grounding pin 7 you put +5v on it. BUT I have never done it this way so I amnot 100% sure.

*edit also use a smaller trimming capacitor than the one shown, that circuit is bigger than it needs to be. You can make it much narrower and then the circuit will sit right beside the video encoder for shorter wires.

[Lastcallhall]

You could yes, that is how it is done (on a model 2) here http://www.damomonster.com/Mod_Pages...gaDriveM2.html.

But you would need the circuit as shown for a model 1. The downside is you *could* introduce video noise as you would need to make the wires to long.

There is nought wrong with "locking" the frequency, I have done it more than a dozen times with absolutely no issue. If you want to lock it into NTSC I believe (and maybe wrong) you would the 3.57(something something)Mhz crystal and instead of grounding pin 7 you put +5v on it. BUT I have never done it this way so I amnot 100% sure.

*edit also use a smaller trimming capacitor than the one shown, that circuit is bigger than it needs to be. You can make it much narrower and then the circuit will sit right beside the video encoder for shorter wires.

Yeah, I definitely got a smaller trimming cap -the foot print is a few cm wide/long. So you're telling me if I lock the frequency, I could still use it to play US/JP games? Also, I did have a question on the crystal - I've never worked with a two pronged crystal before - how do you tell which one is in/out?

Thanks!

[Mamejay]

Have a look at this link
http://www.retro-otaku.com/category/...ations/page/2/
He does a colour correction for 60Hz using the 4.33 crystal.
Just replace this for a NTSC crystal if you are in the US etc and it will display correctly all the time.
The lower pitch sound is determined by the 50/60Hz switch and not the crystal. This just feeds the correct colour frequency into the console permanently in any mode. S-video, composite.
RGB does not rely on this so you should be fine.

[omp]

Also, I did have a question on the crystal - I've never worked with a two pronged crystal before - how do you tell which one is in/out?

Thanks!

Either way mate, there is no in/out. Just chuck it in there and off you go!

And yes you can play any game in colour with this fix. US and Japanese games are the same frequency (different language) Pal is the different frequency one.

JPN F=60Hz/L=JPN
USA F=60Hz/L=ENG
EUR F=50Hz/L=ENG

[Lastcallhall]

Awesome! Funny enough, I had a class tonight that covered this very topic. Thanks, everyone!