Modified CGA to VGA Scaler to accept clean sync RGB SCART

[bencao74]

thanks for the infos! The PSU via scart isn't a power supply the circuit can rely on, sure.

So if I understand you correctly the worst case is that

- RGB Scart pin8 delivers 12V
- Comp Sync and Vsync output is then between 10V-11V (according datasheet, page 2, table electrical characteristics LM1881)

--> some devices can`t handle sync voltages up to 11V

For the scaler GBS-8220 documentation is not helpful here. Doesn't help, have to give a try with 12V here. Hopefully the test will show that the worst case is unlikely.

If there is possibility of a damaging a device with 11V sync amplitude I will sacrifice the scart powering.

For the tests it would be the best to try as many consoles as possible.

In general I recommend using a regulated 5V external PSU. Hence there must be some power supply in the near since this circuit should be used with a scaler. And this scalers needs a external PSU anyway. I`ll make life easy and put a optional external PSU on my page.

[fagin]

My syncblaster cable has the external power option as well as PIN8. I have not had one problem yet by trying the cable on it's own (PIN8 supply), then if no picture, connecting external 12v supply. I have even connected the external PSU even when PIN8 produced the goods.

I have just ripped the lead apart and the PCB is somewhat more than a LM1881!

74HCT
59885ICZ
A shedload of capacitors and resistors

Nothing looks obvious for voltage management.

Should of taken this apart ages ago tbh.

[bencao74]

59885ICZ
http://www.intersil.com/data/fn/fn7442.pdf
another sync stripper

74HCT
is there an suffix after hct?

[dosucol1]

bencao74,

Several game conoles that which had official SCART leads available do apply 12V DC to pin 8 of the SCART lead. Some examples are Super Nintendo (PAL), Sega Master System (French), Sega Saturn (PAL), MS Xbox, and possibly others. The Super Nintendo has current limiting on the line, if more than 2 mA is drawn the voltage will drop significantly. The load on SCART pin 8 is specified >= 10k ohms.

If you draw significant current from this signal line, you should expect regulated 5V, or regulated 12V, or unregulated and current limited 12V (ie. anything between 0 and 12V). What I'm getting at is that anything could be connected to this pin - you can use it as a power source - due care is required. Filtering and regulation are essential. Also note that an LM1881 powered by 12V will deliver sync pulses at a 12V amplitude.

To power something like the EL1883 (whether scart pin 8 is supplying a high +12Vcc or a lower voltage),can a cheap and dirty solution,like a potential divider not be used ?

[viletim]

To power something like the EL1883 (whether scart pin 8 is supplying a high +12Vcc or a lower voltage),can a cheap and dirty solution,like a potential divider not be used ?

Some kind of regulator is required to take an input of 5-12v and ouput something within the voltage range of the EL1883 (3-5v). Also some method of preventing current from an external power source from flowing back through the SCART lead.

Something like this.

Code: Select all

.                       Vcc
.                        +
.                        |
.                   D1   |    D2
. Pin8 ----R1---+--->|---+---|<---- Ext regulated supply
.               |
.               |   D3
.               +---|<---+
.                        |
.                       --- GND

D1/D2 = Schottky diode, D3 = Zener diode

[bencao74]

thanks a lot Viletim

I`ve some spare footprint on my pcb, coz of first version. I try to use them for your schematic. Takes some time ...

[hellbelly]

Just tried out the sync strike today, love it

when I tried my psone on it, it also failed to work with my VGA Scaler, so I removed the power and gnd wires to the modchip, tried again and it worked perfectly. Resoldered the power and gnd wires and it continues to work.

Tried it with my own sync stripper/cleaner and now it works with that. No idea why the modchip was affecting it like that, but there you go!

Thanks to bencao74 for letting me try it, much appreciated!

Pete

[matrigs]

i tried to build this little piece and it works perfectly with a ps2 and a dreamcast, but it shows no picture from a xbox360. of course it has native vga but i'm still curious if someone had similar issues ?

[jaxmazon]

Hi I'm having some issues with building this scaler I have followed the directions and have even followed the advice from previous posts which have all helped however when I plug my megadrive into the scaler I get negative colours and extreme flicker of a faint picture which lasts for around 3 seconds and then no signal . I thought that maybe it was the RGB cable, so I tried using my psone console and rgb cable into the scaler and I get a picture however there is a box at the bottom of the screen and the screen slightly flickers every 5 seconds then after 30 seconds I get a yellow tinge to the screen.

could anyone please guide me in the right direction please?

thanks in advance

[matrigs]

afair in his latest video on youtube about the sync strike fagins mentioned the mega drive to be difficult to sync. i guess that with the 360 it is kind of similar.

[fagin]

Never tried this scaler with a MD, as mine is goosed.

Haven't tried the 360.... Not sure why would want to, to be honest, but I will try shortly.

[fagin]

Just tried the scaler with my 360 and it has no issues.... however this is with the Sync Strike as the sync cleaner. I have now removed my LM circuit from the scaler, so unable to test specifically with that..... but I see no reason why the test result would be anything different with just the simple LM circuit.

[jaxmazon]

Hi I can't seem to get my sync splitter to work with my cga to vga converter so Im thinking of getting a sync striker instead if I do get one will I be able to use my rgb systems with my monitor? and does a normal vga cable from maplins work fine?

thanks for advance

[hellbelly]

Yep, Sync Strike works perfectly with it, and I tried it with a really cheap VGA cable from ebay - bought a couple of 50cm cables so that they weren't too long.

Pete

[ckong]

Yep, Sync Strike works perfectly with it, and I tried it with a really cheap VGA cable from ebay - bought a couple of 50cm cables so that they weren't too long.

Pete

50 cm cabels? Didn't see them yet, but sounds useful. I went another route and ordered some VGA gender changers at Dealextreme, I hope that they give a nice and firm connection between the Sync strike, the scaler and the SLG3000. That way I hope to avoid all the bloody long and rigid VGA cables which give a mess.

[matrigs]

okay it actually works with my 360 - i had to reset the "picture" settings from the ps2 and pressed the "auto" button on the scaler and it works like a charm.

[Kibagami]

Hi everyones,

i faced some issues when i was trying to connect a neogeo to RGBHV connector, i plugged everything as described linked between a rgb scart to a IC with LM1881N but after 2 days working on it the result show a fixed image on screen and this image is clear but not centred, (so i can see three time the same image on screen), do you have any suggestion for this ?

it's looks like to concerne Vertical Sync but i feel a little bit lost.

i am using 640*480 video mode for now.

[fagin]

Rescan the VGA port on your monitor.

I get this problem occasionally with centering and it can be fixed by forcing the monitor to auto adjust again.

[Kibagami]

Hello Fagin,

Thanks for your answer, finally i have tested this card with the SNES it's working properly so i think the matter comes from the neo geo scart where we can find differents resistors who could probably fake the signal, also by working on it i feel totally seduced by this video card and i made a plastic box for it.

but finally i am thinking about how to make a real box, i mean that i am really interested in making a box like an amplifier with
this video card or a better one if i can find one, cumulated with a sound amplifier with gold connectics and also a Led screen on the face of it, i found some good informations about it and will make the box of my dreams ^_^

concerning my problem with neo geo scart i think that i am going to rebuild a wire myself extracting only RGB and Sound, that should rocks this way.

i am also wondering if that's possible to :

- get a better card ? (i have got the version III with only one vga outplug)
- have a better colors render in rgb with SLG3000

Best Regards,

[Kibagami]

also i forgot to answer you concerning your advice but unfortunatly i connected my card to my LCD Tv so i can't force the tv to autoadjust the screen :s

otherwise some mini professional sony monitors could give help, they allow to manage vga parameters and send the signal back to any sources, i am looking to find one as soon as possible if that's possible to find one who isn't too expensive

[fagin]

If it's purely a centering issue, I have been known to have to change the geometry settings on scaler itself, per console. You can adjust screen position on the scaler menu.

[guldberget]

With the risk of asking a "noobish" question...

As far as I understand from other discussions the scaler requires a power source of +5V@approx 2A. So my question is if anyone has tried powering both the scaler and a NeoGeo 1-slot board or a Cave PCB such as Deathsmiles at the same time using a single Ault SC200 psu (output +5V@4A and +12V@1A)? My guts tell me that the psu would be close to its limit with that setup but if anyone has tried it, how did it work ?

[eadmaster]

I still don't get it. Why would you need separate H and V sync when using this scaler. Mine works fine with C-sync and a sync cleaner from Jrok. What's the difference?

This is my dubt also.
Could you explain why such device is required for RGBS component sources?

[fagin]

I still don't get it. Why would you need separate H and V sync when using this scaler. Mine works fine with C-sync and a sync cleaner from Jrok. What's the difference?

This is my dubt also.
Could you explain why such device is required for RGBS component sources?

You obviously didn't read my response directly after your above question was asked!?

[eadmaster]

Sorry, maybe i'm missing something obvious, but i don't get why leaving the "VS" and "HS" pins unconnected won't do "any good".
I supposed that the composite sync coming directly from the SCART pin-20 was sufficient...

[fagin]

Sorry, maybe i'm missing something obvious, but i don't get why leaving the "VS" and "HS" pins unconnected won't do "any good".
I supposed that the composite sync coming directly from the SCART pin-20 was sufficient...

You've lost me......

You can't leave the V and H unconnected.... you won't get any sync signal.

You at least need to have H sync (for composite sync) connected.

If you have composite sync from your source you don't need to clean the signal. If you have composite video from your source, you need to clean the sync.

[eadmaster]

I've found this hires pic of the board for reference.
The 8-pin RGBS connector has the following pins (from left ro right):

Code: Select all

GND
GND
VS = Vertical Sync?
HS = Horizontal Sync?
S = Composite Sync? (compatible with SCART pin-20?)
B
G
R

Btw, why is it called "RGBS" while it also have separate/component sync inputs (RGBHV)?

[hellbelly]

That connector lets you connect up either an RGBS or RGBHV signal, and you select which one you're using by pressing the input select button.

On the underside of the board, you'll see that S and HS are actually linked up.

Pete

[eadmaster]

I'd like to connect some old Nintendo consoles that have SCART output (SNES, N64 and Gamecube).
Can i wire the SCART this way:

Code: Select all

GND <--- SCART ground
GND <--- SCART ground
VS (unconnected)
HS (unconnected)
S  <--- SCART pin-20
B  <--- SCART pin-7
G  <--- SCART pin-11
R  <--- SCART pin-15

?

[fagin]

Yes... as long as your sync is composite sync (and not composite video for sync).