Big problem with RGB bypass mod

H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
Hi everybody!

I recently bought a NeoGeo AES system (the third:) , N°151XXX). But the picture quality was very very bad. So i did the RGB bypass. The problem is that the colors are very strange!:conf: I got a sort of greenish screen with every game. So i soldered 82 ohms resistors, then 120 ohms in vain. I always got this greenish picture. Another strange thing is that when i plug out the scart cable, and then plug it in, i got a very very good picture (really sharp with true colors) but only for an half-second. The same thing happens when the 330 Mega max screen starts to disappear...(when this screen is on, the colors are really bad, but when it starts to dissapear they are really good:conf: )

I've tried everything, could someone please help me?

Thanx a lot.
 
norton9478

norton9478

So Many Posts
No Time
For Games.
20 Year Member
Joined
Oct 30, 2003
Posts
34,075
Arcade screen or TV?

Is your connector set up to Make the TV use RGB and not Composite? You have to throw 3-5 volts on some pin to make the TV use the RGB signal....

It could also be an amplifiacation/capacitance issue...
 
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
My TV accepts RGB signal without any problem. I've never had problem with the slot MV1FZ+supergun that i sold 6 month ago.

For the capacitors and resistors, i've just desoldered those indicated: the three 6.8k resistors, for the four capacitors, contrary of what was shown on the picture(the 2nd) http://www.neo-geo.com/forums/showthread.php?t=92840&highlight=rgb+mod+picture , mine were groupped like that:

Please help!!

Another info: My rgb cable is a NeoGeo CDZ one.

Please please please help.:(
 
Last edited:
MKL

MKL

Basara's Blade Keeper
20 Year Member
Joined
Mar 8, 2002
Posts
3,686
I would need to see a picture of the other side of the board.
 
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
Please dont look at the resistors i've just soldered, i know they are wrong. I'm just trying everything i can.:) That's why i haven't cut the resistors in this test.
So i've tried with 82 ohms, 120 ohms, and on this picture with 8200ohms:loco:

With those one i just have sound, no picture.(i think it's normal)

 
Last edited:
MKL

MKL

Basara's Blade Keeper
20 Year Member
Joined
Mar 8, 2002
Posts
3,686
The picture is unclear. Please remove those wires and resistors and make a closeup picture of just that area (like the first one you posted but solder side), not the whole board.
 
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
I've desoldered it quickly. I go to work( i come back in five hours but i got internet at my job). I assure you that no solder points are touching them. (it seems in this angle, but they're not)



Is this picture okay?
 
Last edited:
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
I've already tried to solder this way with and without resistors, for exactly the same result. I'm waiting for my girlfriend to bring me the cable to my shop to try on a neogeo cdz. I'll tell you as soon as i tried.

Thanx a lot for your help!:)
 
MKL

MKL

Basara's Blade Keeper
20 Year Member
Joined
Mar 8, 2002
Posts
3,686
Once you've rewired as I told you, to see if the cable is also wired correctly, plug it into the board (with solder side facing up) and with a multimeter check continuity across the points of the same colour. One of the blacks on the scart is enough. And across the pinks you should read 100ohm or so.

http://img522.imageshack.us/img522/2640/immagine3bg4.jpg
 
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
The problem is that i don't have a multimeter. Would you do it for me or look if you could do something if i send you my NeoGeo? If you can, tell me please how much would it cost me? If you can't, i'll look for a multimeter.

Thanx
 
norton9478

norton9478

So Many Posts
No Time
For Games.
20 Year Member
Joined
Oct 30, 2003
Posts
34,075
Solder a Scart cable directly to the Resistors/CXA chip....

See what happens.

Also, Clean that solder work up....

I see many potential shorts...
 
Xian Xi

Xian Xi

JammaNationX,
15 Year Member
Joined
Dec 1, 2005
Posts
27,762
hxcseb said:
I've already tried to solder this way with and without resistors, for exactly the same result. I'm waiting for my girlfriend to bring me the cable to my shop to try on a neogeo cdz. I'll tell you as soon as i tried.

Thanx a lot for your help!:)
Click to expand...

I would first fix that crap soldering job just incase. I see 2 blobs that look like they're tuouching the pin next to them which might be causing a problem.
 
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
Looooooooooooool! I know i'm a dick in soldering, don't refer to what you see, that was the 20th time that i resoldered. Loosing my nerves, i didn't took the time, that's all. Now soldering points are nice.
So i looked in the scart cable, and two wires were inverted, the pink and the yellow. So i changed them, and now i got no more parasites in my home cinema (sound), but the picture appears really good for one second, then roll over the screen, and then dissappears.

Any idea?

Thanx to you all!
 
norton9478

norton9478

So Many Posts
No Time
For Games.
20 Year Member
Joined
Oct 30, 2003
Posts
34,075
I'm guessing it's an issue with the Neo-s crap sync.......
 
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
Another question: Could it be the fact of the AC adaptator i use? I use a GameGear one, output DC10v 850mA instead of the SNK one, output DC10V 1000mA. I've never had problem with it (GameGear one) before the mod.

Thanx
 
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
I resoldered everything for the XXX time...



and always got this greenish screen...



As you can see NeoGeo 330... appears pale green instead of white. The blue of the SNK logo is very pale too.

I don't understand, everything seems to be ok:very_ang:
 
MKL

MKL

Basara's Blade Keeper
20 Year Member
Joined
Mar 8, 2002
Posts
3,686
It's possible that the resistors where you tapped the RGB signals from got damaged and their values altered so that you get more of one colour than the others. You should measure each of the 21 RGB resistors and see if their values are correct and in case replace those that are not. So the problem seems to be more serious than I had previously thought.

This reminds me of this thread:

http://www.neo-geo.com/forums/showthread.php?t=78595
(the problem here was at an earlier stage though)
 
Last edited:
B

bamarquez226

Crossed Swords Squire
Joined
Mar 2, 2007
Posts
183
MKL said:
It's possible that the resistors where you tapped the RGB signals from got damaged and their values altered so that you get more of one colour than the others. You should measure each of the 21 RGB resistors and see if their values are correct and in case replace those that are not. So the problem seems to be more serious than I had previously thought.

This reminds me of this thread:

http://www.neo-geo.com/forums/showthread.php?t=78595
(the problem here was at an earlier stage though)
Click to expand...

The unfortunate thing is he mentioned that he has no access to a multimeter earlier :oh_no:
 
Xian Xi

Xian Xi

JammaNationX,
15 Year Member
Joined
Dec 1, 2005
Posts
27,762
hxcseb said:
Another question: Could it be the fact of the AC adaptator i use? I use a GameGear one, output DC10v 850mA instead of the SNK one, output DC10V 1000mA. I've never had problem with it (GameGear one) before the mod.

Thanx
Click to expand...

I thought the official SNK PSUs put out 3A max not 1A. :conf:
 
H

hxcseb

n00b
Joined
May 4, 2007
Posts
14
I'm gonna buy one tomorrow morning. I hope the problem is one of the RGB resistors as MKL said, and not a deeper problem. Before the mod, everything was working fine (composite or RGB, but with a bad quality of course).

 
Last edited:
Xian Xi

Xian Xi

JammaNationX,
15 Year Member
Joined
Dec 1, 2005
Posts
27,762
Interesting, thanks guys. Something new everyday.
 
segasonicfan

segasonicfan

Camel Slug
Joined
Feb 3, 2006
Posts
524
12v is only 1 amp if the audio is on full blast ;)

I don't know much about this mod but it seems to me that this is overly complicating things. Doesn't the AES RGB pass through the CXA1145 for clamping before sending to the output jack? Maybe drawing the RGB before this circuit would fix things? I also find replacing the RGB caps before the CXA chip to be very useful for increasing video quality. If all else fails I would suggest using opamps for the RGB lines. this can fix a lot of problems as well (I find the EL5410 to be a great circuit for this). Check my CDX modding info on my webpage for info. The CDX and AES do pretty much the same thing for video (MB3514=CXA1145).

-Segasonicfan
 
You must log in or register to reply here.
Top