Megadrive Stereo mod?

Well after a lot of trial and error (turns out I hadn't cut the traces deep enough) I eventually completed the region and frequency mods on my MD1.

Even though I've played Sonic 1 in 60HZ mode emulated it's the first time I've played it this way on native hardware. Flicking back to 50hz it's truly shocking to see what the PAL consumer was playing with.

It was an absolute bitch as I have a VA4 motherboard (the early one) which means my solder points were in completely different places and order to the MMMonkey guides, I also had a capacitor on JP1 to deal with. It's the second time I've ever soldered in my life and seeing as I used a cheap £9.99 30W iron I think I did a good job.

I ended up mounting the dip switches to the left of the volume slider and they look awesome, almost as if they were meant to be.

Anyway I was wondering if there was a way to route stereo from the headphone jack to the DIN connector? I've got myself a nice new Scart RGB cable but of course the port only outputs in mono. I really don't want to have a wire coming out of the front of the system.

If there's a way to do this please help. Other wise I think I'll invert the headphone jack and run a phono cable to the back of the case and mount it there.

EDIT: I'm aware you can do a mod where you can run a cable from the headphone jack to a custom scart cable but I'd like to know if it's possible to do it internally, i.e where the DIN C meets the board.

 

you could cut a trace to the DIN connector that you don't need and wire the other audio channel to that pin... but no easy way i can think of

 

Ok next question.

Is there anyway to get RGB quality through a single yellow video cable rather than scart and wire it up to the DIN.

This way I could run male to female red and white cables from the phono jack at the front to the back of the system. Then run the three cables together into a scart block adapter and into the TV.

I'm just looking for the neatest possible way to get Stereo RGB.

 

http://www.gamesx.com/avpinouts/genesisav.htm

8 pins on the first model and 9 on the second with the additional pin used for the sound channel not available on the first model.

http://pinouts.ws/scart-pinout.html

Looking at the SCART pinout I'd check to see if pin 2 (right channel for stereo) is connected to anything on the Megadrive side. If it's connected to one of the grounds you might be in luck though there is a chance they just left the wire out of the cable or have that pin grounded on the connector side or something of the sort.

EDIT: Just saw your new post.

RGB needs at least four wires to actually be RGB otherwise you've got composite to run along one "yellow" cable.

 

It's definitely a stereo cable as I specified this when ordering it and I had a choice, so it's likely to be connected to ground OR whatever the Neo Geo uses as they're cross compatible aren't they?

Even though I knew I'd be getting mono from the MD, the cable might come in handy for something else.

I might just add the female audio sockets on the back of the system and use a separate sound system which I do for most of my games anyway.

If I take it anywhere mono isn't the end of the world.

 

Grab something that can check for continuity and see where the L/R channel pins on the TV end connect to on the MD end. I'd bet you could wire in the extra channel without causing any real problems.

Though I'm not exactly sure if the MD outputs L/R mixed into mono or if it outputs just left or right and calls it mono. If it's the former you'd need to cut the line going to both and wire it up to the headphone jack I suppose. Or tap it directly from the chip that pipes the audio out. Should be easy if everything cooperates and you have a soldering iron handy.

 

It's L/R mixed.

The headphone jack on the board is just two pins left and right. If I solder two cables directly to those points will that mean I'll lose use of the headphone socket as the audio will travel to the phono first or will whatever is plugged in take priority?

I'm guessing the former as I'd probably need to integrate something else to make it a parallel circuit rather than a series.

I'm prepared to try whatever really. This MD is in a bad way and I bought it today for £10 and I have a much better one coming from Grey Fox as soon as the royal mail find it. So I'm prepared to totally fuck the board and case up with experiments.

 

I'd guess that if you just tapped the pins on the headphone connector and didn't cut/short any traces BOTH should work just fine. At the same time even. Total guess but I can't think of any reason off hand that it shouldn't work that way.

Assuming the headphone jack isn't one of those that when nothing is inserted there is a mechanical bit that shorts across the pins and pipes the audio to the back of the MD. I vaguely recall someone mentioning something to that effect before, all it would mean is that if you use the headphone plug that you wouldn't get audio output from the rear connector which I'm sure can easily be bypassed. Likely by tapping the chip's output traces.

 

Well only one way to find out. I'll try it out tomorrow.

 

Might be worth PMing TmEE as he's the resident Megadrive expert. I know he did a "crystal clear audio mod" to his, and he's pretty forthcoming with schematics usually.

 

Was just giving his modded MD2 thread another look.

I'll drop him a PM and see what he says.

 

Good job on the mod by the way! I wasn't aware that different revisions would need different instructions or I would've warned you. Seems like you managed it anyway

 

x

 

It won't take me long to figure it out at all when the case is open, just I've shut down shop for the night and thought someone might Know the answer straight away. I'm just being lazy.

I've chosen the MD1 over the 2 purely down to aesthetics.

I've decided on the phono plug mod. AFAIK it's never been done before, maybe because it's kinda pointless but it will look good if done right and add a little more flexibility.

I'll go parts shopping tomorrow and see what I can do about shielding.

 

uh, i've run the audio from the headphone jack out to rca jacks on the back... it's super easy and fairly common.

 

Uhhh... if you're going to do that but wanted it through the TV, why not make a SCART to Mega Drive + audio cable? You know how the PlayStation etc. RGB leads have a box on the lead with phono sockets? You could do that, only they're wired to the SCART socket, not the DIN socket. Then put phono-phono leads from the console to the box. Or simpler (if you can fit it in, which you should be able to) a second lead with stereo phono connectors.

 

Because if I have a scart going into the TV and phone cables as well. There's no way to tell the TV to take audio from the phone and not the scart.

Anyhoo my second MD arrived today however I wasn't able to get any parts so it'll have to be tomorrow when I decide what to do.

 

Wire the SCART L & R directly to a male 3.5mm TRS for plugging into the headphones jack. It's cheaper than RCA jacks and best of all the MD doesn't go under the knife.

 

Do you need Composite video out? If not, you could cut the trace going to pin 1 of the DIN socket and wire it as an audio left. then you could cut the mono audio (pin 3) and wire it audio right. Then wire up your SCART acordingly.

Hope I helped!

 

what video encoder chip have you got?