Megadrive (japanese) ->XRGB-3, cable configuration

[kamillebidan]

Dear all,
thank you for your great forum.
I have a japanese megadrive, and I bought an xrgb-3.
I connected them with a cable. Following the ping numbers of http://www.gamesx.com/avpinouts/genesisav.htm and http://junkerhq.net/xrgb/index.php/RGB21 the cable is as follows (MD=mega drive, X= XRGB-3)

M7-> 75ohm -> 100uF -> X15 (red)
M3-> 75ohm -> 100uF -> X19 (green)
M8-> 75ohm -> 100uF -> X20 (green)
M5-> 180ohm-> X16(+5v)
M4-> X21(ground)
M2-> X9 (sync)

The cable works,but I have the problem that XRGB looses the sync (it jumps from 15Khz to 31 etc) with white flashes.
I then replaced the connection M2-> X9 (sync)
with the connection M1->X9

But when I do this, I get that XRGB finds the console (it does not say no input,as when I disconnect) but the screen is totally black. If I revert to M2-> X9 I still see the image.

Do I need to change something in the RGB21 as well?
Do I need to set something in the XRGB-3?

Thank in advance

[Fudoh]

On the XRGB you don't need a +5V line.

For raw sync to work from a MD/GEN1 model you need a 220uF capacitor in line with the sync signal (+ to MD, - to XRGB).

Also you don't need the capacitors on the RGB lines, instead you might want to raise the resistors in the RGB lines to 180 or even 220 ohms per line.


That's the way I connected my MD to the XRGB-3 for years and now the XRGB-Mini.

[kamillebidan]

thank you for the prompt reply!
I will try and let you know as soon as possible. How many volts should the capacitor be? 6.3 ?

[Fudoh]

doesn't really matter. I think 10V ones are pretty common....

[RGB32E]

Your thread title is a contradiction. The term "raw" is a misnomer used to describe CSync.

[kamillebidan]

Sorry,I thought pure=raw, as in
http://www.videogameperfection.com/2011 ... s-at-last/
I now changed

[BuckoA51]

It does. Thread title should be "cvideo for sync works"..perhaps... all very confusing.

[kamillebidan]

Thank you Fudoh, putting the capacitor the cable woked.
For the R G and B lines, I tried two versions, 1) 75ohm resistor+capacitor and 2) 220ohm resistor.

WIth the settings suggested here ,
http://junkerhq.net/xrgb/index.php/XRGB ... d_settings
for the Megadrive, the 75ohm version looks better,because the image is pretty dark with the 220 ohm version.
Did you use any particular setting on the XRGB-3?

[Fudoh]

I can't remember, sorry. In the end I only used the RGB input on the back. For the front input you have a terminations witch (75/220) in the menu.

[kamillebidan]

I summarize some of the results I got

Configuration
Japanese Mega drive model 1 - XRGB-3

Config 1: composite as sync
using games with flashes (ex. Micromachines military) cause problems to the XRGB (it switches to inputs other than 15KHz)

Config 2:csync (hsync+vsync) through a 220uF capacitor
Depending on the XRGB-3 AFC level:
AFC 0 to 2: some games (expecially sms ones) show a deformed image .The top raws shift toward the right, forming a black ")" on the left edge and a ")" bump on the right edge
the image is perfectly still
AFC=3: the games get perfectly aligned, Howver with static images, you can notice a "trembling" of the images, right to left and viceversa

is this a known problem?

[RGB32E]

I recall this being discussed in the XRGB-3 thread. With a MD1 my cable was configured with a 100uF cap on the CSYNC line and connected to the RGB21/Game input. However, I was using B0 mode and not B1.

[kamillebidan]

Thanks, I will try and let you know.
Did you play SMS games as well ? It seems me the problem is stronger with SMS games than MD games

[BuckoA51]

it's a known problem, http://junkerhq.net/xrgb/index.php/Master_System. SMS is especially problematic on the XRGB3. Megadrive/Genesis games should be perfect when using pure csync though.

[kamillebidan]

Thank you Bucko, this is exactly my problem.
I wonder what the real reason is, and if it can be solved with any circuit (e.g. lm 1881, particular resistors / capacitors on the cable, etc).
Furthermore, this reports my same case, Sega Megadrive (NTSC/Japan) + Everdrive

I wonder if the real SMS has the same problem

[BuckoA51]

I tried all kinds of things from sync strippers/splitters like the sync strike to Extron RGB interfaces. The Extron helped a little bit but nothing was completely effective.

[kamillebidan]

Thank you, I just found your post on the xrgb-mini thread

Oh okay thanks, my Everdrive performs exactly like the real SMS converter with Master System games, i.e sync dropouts or warped screen top, though the Extron helps.

Did you buy try the mini as well? Do you know if it solves the problem?

In the xrgb-mini thread, I found

Oh, wow. 240p processing looks fantastic. Have you tested the Master System?

I don't have one, nor do I have a MS converter for the MD. I tested MS games on a Everdrive before (on a XRGB-3) and they worked fine, so this version should work on the Mini as well....

I wonder what the difference is...

[Fudoh]

Oh okay thanks, my Everdrive performs exactly like the real SMS converter with Master System games

I remember having dropouts on the MD/Everdrive combo as well. Can't really remember what I changed after that - possibly a LM1881 into the RGB cable ? Anyway, after that the sync problems were gone - for both MD and SMS games. It's possible that SMS required a higher AFC level, but not to a degree where it gets extremely shaky. I've always had an Extron interface between the XRGB and the TV Set though.

[kamillebidan]

Oh okay thanks, my Everdrive performs exactly like the real SMS converter with Master System games

I remember having dropouts on the MD/Everdrive combo as well. Can't really remember what I changed after that - possibly a LM1881 into the RGB cable ? Anyway, after that the sync problems were gone - for both MD and SMS games. It's possible that SMS required a higher AFC level, but not to a degree where it gets extremely shaky. I've always had an Extron interface between the XRGB and the TV Set though.

Thank you fudoh, yes, in the xrgb-mini thread you mention having an LM1881 indeed.
On the contrary, I have no dropouts (=the XRGB changes the expected input frequency, isn't it?) even without sync strippers. I had dropouts using the composite as sync signal, but since I switched to csync It works nicely (thank you again for teaching me of the capacitor!)