Question about RGB modding an Amiga CD32 console

[bacteria]

If you do searches on the internet for RGB modding an Amiga CD32, it refers to tapping off TP9 pins, and of the 10 pins there, if we take pin 1 as the one closest to the center of the board and pin 10 as the closest to the edge, then pin 6 is Rgb, pin 7 is rGb, pin 8 is rgB, pin 9 is C-Sync. Ok, that's fine, but it also states the RGB lines are not amplified, and weakened by the S-video connection; so a good idea to use a 47 ohm resistor on each of the RGB lines, and ground pin 174 on the expansion pack traces.

Ok, however, there is a Sony CTA1145M chip on the CD32 board, which is designed to input RGB and output composite and S-video. I know from the Sega SMS and the NEC Turbografx that you can tap RGB straight off this chip.



Surely, tapping off pins 11, 21, 22, 23 is the better option here?

Comments?

[bacteria]

So, tried RGB from the Amiga CD32, tapping off the Sony CXA1145M chip. It is designed normally to take in RGB and covert the output into S-video and also composite. This chip is a lovely chip if you have it on a board, as it means you can output RGB easily, irrespective of if the console only claims normally to do RF. It was therefore very easy to RGB on the Sega SMS, was really handy on the UK version of the TurboGrafx for the same reason (the PC-Engine needs the RGB lines amplified normally), and on the Amiga CD32 too. If you tap off the TP9 lines, as seems the usual method, then the results are supposed to be poorer as the S-video conflicts, tapping off the CXA1145M chip makes this issue redundant.



Here is the output on a PSone screen, RGB mode. Using one of these screens for testing purposes, so I know RGB works before later in the project I wire all video modes to a Scart socket. The pictures came out fine; the image on the screen certainly looks crisp and nice. Camera pics are slightly out of focus!





Audio can be tapped as usual from the left and right audio plug contacts on the Amiga board.

[TmEE]

The problem with RGB off CD32 is that the black level is all wrong. But it can be fixed with 3x 100Kohm and 100ohm resistors ^^

My CD32 went shot though when I was doing a dual kick mod, so I'd not have to juggle with different chips if I wanted KisckStart 1.3, 3.1 or the original CD32 ROM... but now things don't work, makes me think that I have fried an address line of some chip D:

EDIT: a pic of the fix :
http://www.fileden.com/files/2008/4/...oardBottom.jpg

when I get home i'll see what exactly did I do

[bacteria]

Did you take RGB off the chip or from the TR9 pins? Off the TR9 pins gives the issues.

What's the "dual kick mod"?

Won't your resistors make the screen look dark?

[retro]

It was therefore very easy to RGB on the Sega SMS

Yeah... plug an RGB cable into the socket on the back! ;-)

The Master System II, however... ugh, why bother? It can't play all the games. plus you lose RGB and the reset button! Oh, and the expansion slot... if you have a use for it!!

[TmEE]

Did you take RGB off the chip or from the TR9 pins? Off the TR9 pins gives the issues.

What's the "dual kick mod"?

Won't your resistors make the screen look dark?

I took RGB off the same spot as you did, from the CXA.

And the resistors won't make the image darker, except for dark tones which are otherwise grey or too bright. White stays white, black turns from grey to black ^^

And dualkick as in I installed another socket next to the existing Kickstart ROM and made it so I can launch other Kickastarts from it. MY idea was to have KS 1.3 and 3.1 in the 2nd socket, and CD32 KS in its original place, and 2 jumpers to select between the 2. I was turning my CD32 into a A1200...

[code]original :
DAC RGB out o------||-------o CXA RGB in

modified :

DAC RGB out o---[ 100ohm ]---||----+--o CXA RGB in
|
GND o---[ 100Kohm ]---+[/code]

EDIT: crap, ASCII drawings won't work... anyway, the 100Kohm resistor goes to GND after the cap before CXA RGB inputs.

[bacteria]

So, what resistors did you attach to the R, G, B and C-Sync; and is the resistor between the wire from the pins to the screen board, or do the resistors connect to ground instead? More info please!

Normally, when you add a resistor, it makes the image darker, eg used a 36ohm resistor on composite to ground on the GameCube as that makes the image to the right level (it is too dark otherwise), that is what was in the original Nintendo A/V jack when I opened it up.

[TmEE]

These resistors are on the RGB lines going to the CXA not coming out, you can have a 1K resistor there and not have any remarkable change in brightness. The resistors are only on RGB lines, sync is completely untouched.
100 ohm resistor is in series with the line, but before capacitor, 100Kohm resistor is after cap, and going to GND... I cannot explain it in any more simpler way.

[bart_simpson]

C sync wheres it on a scart for a tv please help thanks.??

[Lum]

Yeah... plug an RGB cable into the socket on the back! ;-)

The Master System II, however... ugh, why bother? It can't play all the games. plus you lose RGB and the reset button! Oh, and the expansion slot... if you have a use for it!!

It turned out having anyone else add RGB to Master System II isn't worth the expense for me. After labor and post both ways, it'd cost more than an SMS.

[retro]

bart_simpson - composite sync is carried on the composite line.

Lum - modification costs money. Therefore, you would expect a modified console to cost more than a stock console. Likewise, if you want the improvement, you pay for it. You can't really compare the cost of an unmodified console to having the modification done. My friend had some kind of Dolby upgrade done to his Denon amplifier years ago. It cost £650. The amp was probably worth about £1,200 at the time. Nowadays, it's worth a couple of hundred, maybe... but the mod (if Denon still do it) would still be a lot more.

However, I would agree in this case that if you could pick up an original Master System for less, it'll play card games AND have RGB out ;) I've never liked the MS2 anyway.

[Lum]

Right. My comment excluded the console's price. But that doesn't change anything. When it saves money to buy another whole console than upgrading one I already own... The choice becomes rather obvious.