Yet another Genesis/Megadrive mod - Video Selection board and Switchless Mod

Quick update:



I've nearly finished to solder all the components.
I've some minors things screwed up (the button is a bit too big, some drill's holes are to small, etc.) but it seems everything is quite ok. The switchless board is also working.

I've also finally tested my Aoyue 474A++ Desoldering Station. After testing a bit and felt disapointed, I turn it up to 400° and... wow. I don't think I could go back to desolder wick anymore.

I'll be busy until saturday, I'll update the thread when I'll add the boards in the console.

 

It seems this thread doesn't generate much reaction, but hey, quick update anyway.

So I've prepared some wires.


Also I've quickly tested the swithless board in the console and it works! Yay!
No pics yet, more to come this week-end.

 

I enjoy the updates and pictures of the progress so don't let no replies keep you from posting.

 

^

 

Thanks guys.
Here's the daily update.
I've modify my MD for accepting 5mm LED.


Yay! Set in Japanese :


Here's the board installed in the console:


Unfortunately, the headpins on the motherboard for the board plus the headpins for LED/MegaCD/32X/Reset Switch make the whole thing a bit to high. I'm considering using 90° headpins for LED/32X/etc. and definitely solder the board with shorter headpins.
Tomorrow I'll take a look on the reset switch and maybe make some preparations the videoboard.

 

This awesome build log should get more participation.
I really enjoy your ambitious modding and neat work.

Btw:

I also got an Aoyue desoldering station recently, mine is the all in one 2703a+ but the desoldering gun is the same I think. Very nice upgrade isn`t it?

In my personal experience 350C is enough heat though. Try it and see if it works for you. Less heat = stress on sensitive components.

 

Thanks Max.

Yes is a really nice upgrade. I've test and 380° seems fine.

So.

I've screwed up the reset board: the original switch is smaller than the new one, so I had to create an adapter.



As I thought, I had to cut a corner to fit with the frontjack board AND I had do move a bit the capacitors next to the reset switch.
It fits tight but It won't move though.




As I also expected, the new reset switch is too high, so I have to chop-off a bit the reset from the shell. In order to make it reversible, I add a screw: like that, I've just have to adjust the position of the screw to make it longer.

(sorry for the over-exposed picture)

And...

Voilà!!



RED: US
BLEU: JAP
GREEN: EU

First step is working.

Next I have to test the video board.
After thant I'll order the components for the switchless multibios MegaCD. I'm still think how to connect the 32X to my board in a different maner than using a trace from the din-9 like mmmonkey.

 

Annnnd I've just broke my last tip for my soldering iron.
Also, I'm still fighting to remove the cxa1145p even with the desoldering gun: it seems soldered from both sides and it's hard de remove everything. The chip is still firmly in place despite all my efforts.

 

Probably the legs going through the ground plane.

Awesome project - a first revision MD would really get your setup looking fancy though. Pedantry!

 

Thanks Segata!

Finally! I didn't wanted to stay on this state. I found an old tip for my solder. A HUGE one. After using some desolder wick, I decided to use a needle and "break" the solder left around each pins of the CXA.

Ta-da!

CXA on socket! Everything is working.

It's 2:00am I'm gonna sleep. ^^



EDIT: HO GOD!

The CXA is inverted upside-down between the VA3 and the VA5... my board doesn't fit in my VA3.
That's it I'm gonna sleep...

 

Revision'd!

 

Ok I'm totally lost.
I've tried (by stacking multiple sockets to be higher enough and be above the capacitor and the RF box) to plug the video board and it doesn't work at all.

I mean, I tested the board toroughtly: the 74HC4052 logic, the continuity and the voltage and everything is working as it should:
When "off" the circuit let the original signal from the motherboard to the CXA,
When "patch" S0 and S1 allow the original signal if identical, if not, use the Crystal circuit entry selected by the NTSC/pal switch.
When "overide" S0 and S1 are always different and use the selected Crystal circuit.

I've tested multiple times, and yes, the 74HC4052 is doing exactly that.

But I've always black & white screen. I've started to doubt about I swapped the NTSC and the PAL Crystal, so I've changed the PAL in order to have both NTSC just for testing, but no.
After that I've thought it was maybe the zener diode, but since I'm using only ground I don't think it would have an impact.

Something wrong in my desing but I don't see what. I'm now thinking that:
a) both Crystal circuit are interfering each other like make a one strange signal, but I carefully made 2 separated circuits.
or
b) something's wrong with the variable capacitors. I can't mesure them if I don't remove the diodes (more precisely, if I don't remove the link to the ground from the circuit). My capacitor meter tries to calculate but can't managed to. If I remove the link to the ground (removing a bridge or the zener diode) that works.

I'm stuck. If someone could help me or have an idea it would be great.

I've already made a version of my video board for VA3/VA4, but I won't order them before being sure that my current design is working.

For now I'll order the Eeprom for the MegaCD and move to the next step of the swichless mod.

 

Ok, so I made a LOT of tests. Like a BAZILLON of tests.


The tower of the death.

So first, diode is a bad idea. It seems the crystal circuit needs a ground in both ways.

and two, YES, my board IS working. BUT not when the system boots up on PAL.
I remove the PAL circuit and use only the NTSC one for testing.

I've got this at the best:



If I got trought the switchless mode PAL --> US --> JAP --> PAL, then I got the colors, and yes it comes from my circuit: my Crystal cuircuit seems to output a better signal than the original one.
Also when in pal at this moment, the image is bit too low and the bottom of screen is cropped (you can't see the number of lives in Sonic for exemple).


So now it seems the system doesn't use the properly the circuit when it boots up.


Now I need to test with adding again the pal circuit and see if 1) the diode is really a bad idea and 2) having both cuircuit without the diode will make noise between then. If it the case, I'll have to redesign a board and use the switch or something to totally isolate both cuircuit when they are not used.

 

So, I think I'm touching the problem.

I've linked the genesis to a SCART --> HDMI adapter, which is auto-detecting the signal.

When the console is running in NTSC, there's no problems, with the original circuit or mine (one again, mine's offering a better quality, since I guess I'm closer to a true NTSC signal)

But when I'm changing into PAL, even if the pin 7 of the CXA is linked to +5v, the signal sent is PAL.

So it's like the CXA continue to work as usual, wherever it's receiving +5V or GND.

This will explain why I'm not having anything, since the CXA is working on PAL and receving a NTSC Crystal.

Did anyone have an idea?

 

I'm out of ideas for the CXA1145P.

It seems the signal sent is PAL even with the +5V on pin7 and the 3.57MHz Crystal, but I'm not progressing a bit on that.
The only states I have are still:
* colorbars on cool boot.
* full and nice colors but with screen moved down when go throught the cycle JAP --> PAL.


I've started to think that maybe there's a link to ground or capacitor (or a missing capacitor) somehow linked to the behaviour of the pin7 and the CXA. I'll test every traces around the CXA on the motherboard this week-end.

Can't find anything on the subject cause the pal 60hz mod in a US Genesis (in the contrary of a LOT on PAL Megadrive) doesn't seem to be popular.
I'll take a look on NeoGeo, MasterSystem or Playstation which are using the same video chip, maybe I'll find some inspiration.
I also remember seen Demomaster restoring a PAL asia on youtube, I'll have to check his videos.

In a last option I'll buy a CXA1145P and make some Frankenstein experiments. You know, for SCIENCE! ****Mad Scientist laugh****

----------

On an other subject, I've received a small order from Digikey (which I'm starting to love more and more)
And with the tips for my iron solder (and some regulator for SNES cart mod incoming) I've bought those little cute things:



I'll use those for internal connexion of the 32X with something like this:



This is just a photo with the right angle to what I'll do. Cut of a bit of the shell of the 32X for the flat part, and the thick part will be in the genesis next to the cartridge slot (just a slight cut to do in the plastic which is holding the dust cover).
Now I have to find a way to fix the thick part on 90° from the motherboard.

Also, EEPROM and some stuff are coming from BuyICnow for the MegaCD mod.

 

I'm continuing my monologue.

I've resoldered the PAL circuit and... it works perfectly and the diodes are doing their jobs.
More than that, it IS working on override mod, which means I can make the console wokring in PAL/NTSC 4.43MHz.
So:
- PAL 4.43Mhz is working even on my NTSC console.
- Something interesting, when turning the console in US/JAP, my SCART --> HDMI adapter tell me that I'm in.. NTSC 443... which is PAL60Hz. And I'm having perfect colours.

So my board is working BUT there's an other video information since I'm still getting PAL60Hz and NTSC50Hz which are something I wanted to erase. I'm missing something.

EDIT: I think I got it: Could this be due to the C-Sync? (which is coming from the VDP YM-7101)? The C-Sync will set the NTSC/PAL thing, and the crystals only the colours. That will be explain why even with a patch and the CXA-1145P set to NTSC, the video out still sending the signal PAL as a sync and NTSC as colours. Is this possible or am I telling nonsense?

EDIT2: Funny thing, the Genesis in PAL60Hz is working flawlessly on my LCD TV.

 

Let's continue the mod willya?

After tearing down the 32X, let's see if the connector will fit in that

Not bad. Some cut and kynar cable should be thin enought to be under the ground shield.

So let's prepare some marks for cuting the 32X:


And on the dust-cover of the Megadrive:

 

Wayt to go keep it up! Hope you do a youtube Demo of the thing and all functionalities once you are finished.

 

Thanks. There's nothing complicated here. Mmmonkey did the same thing for the switchless mod. I'm just doing it in my way.

The video board mod is kinda compromised since it doesn't override PAL to a full NTSC/60Hz as I wanted to.
I'm just putting on hold for now. I've already removed it from my MegaDrive.

But since my LCD TV seems to accept PAL 60Hz (Sony Bravia KDL-46EX500), I may come later with a new similar board with a slightly different behaviour, because the colours were WAY better (also make disappear rainbows and colours bleeding).
But I'm not used to NTSC stuff (I'm from France, so I'm more used to multi-standard PAL/SECAM) so I just need to test on others NTSC TVs if possible.
And a different layout for Va3/Va4 and Va5/Va6.

A video, sure why not. Like that everybody will hear my prepubescent voice and my horrible french accent!

 

Haha, like this guy?
https://www.youtube.com/watch?v=ao-GVdbLKdQ