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Author Topic: Making a RGB scart cable for a JPAC  (Read 317 times)

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bimm25e

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Making a RGB scart cable for a JPAC
« on: September 02, 2017, 02:18:16 pm »
Hey gang, I am trying to make a female scart to male vga cable to let me hookup rgb modded consoles through scart cables to the jpac hooked up to my cabinets Jamma harness.

I have a female scart port, and the vga port, but I'm not sure what pins to connect where, particularly the h and v sync.

Any advice is appreciated!

bimm25e

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Re: Making a RGB scart cable for a JPAC
« Reply #1 on: September 02, 2017, 04:05:23 pm »
First thing I'll be hooking up is a US ps3 via SCART

buttersoft

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Re: Making a RGB scart cable for a JPAC
« Reply #2 on: September 03, 2017, 10:38:02 pm »
SCART is RGBS+ground. Red, Green, Blue, Composite-Sync, and a ground connection. Composite video or Luma will often do for sync as they each contain video information over composite-sync. VGA is RGBHV+ground. Red, Green, Blue, H-sync, V-sync, and a ground connection.

I can't tell if the JPac will take an RGBS signal, there's nothing saying it will. Which means it needs RGBHV, which is what a PC outputs for analogue video. You can use an LM1881 chip to split sync from a console, just feed composite sync or luma in, if that's all you have, instead of composite video. You get out vertical sync and composite sync, and you use the latter where you need horizontal sync on VGA. This is assuming the JPac will like it. Most things do, but without confirming you're taking the risk it won't work right. You can ask Andy from Ultimarc, he as a rep for being really helpful.

Google the pinouts for VGA and SCART. Then google more, and compare. Don't mistake JP21 for SCART, and make sure you have an up to date version of VGA. Wikipedia is ok for this stuff, but tends not to have great pictures.

Then you look at those pinouts and work out what goes to what, red to red, blue to blue, etc. Use 75ohm coax where possible, and connect the screening to ground. Most often the ground lines are all connected together at each end inside the PC or monitor, but test this with your multimeter to confirm.

This excludes audio, which you will have to break out separately, as the J-PAC won't take it via the VGA D-SUB plug.

« Last Edit: September 03, 2017, 10:41:26 pm by buttersoft »

bimm25e

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Re: Making a RGB scart cable for a JPAC
« Reply #3 on: September 04, 2017, 01:12:09 pm »
Great info thank you, I stumbled across the lm1881m chip yesterday and as starting to read up on it, but does that chip produce an h and v sync?


I have a second option, I have a Jamma to scart pcb thingy that will put the ps3 image on the screen but doesn't sync, I am thinking if I can add the lm1881m to this board I could skip the jpac and go direct Janna to scart

bimm25e

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Re: Making a RGB scart cable for a JPAC
« Reply #4 on: September 04, 2017, 10:35:42 pm »
https://68kmla.org/forums/index.php?/topic/21168-from-composite-sync-to-h-and-v-sync-for-vga/

Good info here regarding splitting h and v sync after the lm1881m circuit.

The writer goes on to say how the lm1881 isn't a 'true' hsync signal though and that's no good for me.

He recommends building a circuit out of an EL4583 to get true sync signals, I'm looking at ordering the chip, but I have no clue what to do with it.  Time for some circuit homework


https://www.intersil.com/content/dam/Intersil/documents/el45/el4583.pdf
« Last Edit: September 04, 2017, 10:50:59 pm by bimm25e »

mourix

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Re: Making a RGB scart cable for a JPAC
« Reply #5 on: September 05, 2017, 08:03:45 am »
This says it will pass through the sync. No information on which pin, though.

Quote
If all jumpers are removed, the J-PAC will pass through composite sync. This mode is used with our console adaptors.

bimm25e

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Re: Making a RGB scart cable for a JPAC
« Reply #6 on: September 05, 2017, 01:08:03 pm »
Thanks!  that led me to this: "If all jumpers are removed, the J-PAC will pass through composite sync. This mode is used with our console adaptors."

which led me to looking at console adapters AND THEN finding they make a universal input cable (which looks perfect for my SCART application...maybe)





So Ultimarc has a product listed, but its out of stock and the info link doesn't seem to point to any specifics.


anyone know anything about ultimarc's: Universal AV to J-PAC/Speaker Adaptor PCB


Cause that thing looks like its close to what I need, but Im concerned about it not separating the c-sync from the c-video and the jpac not liking it




just found this:"OK I have just heard back from Ultimarc. The circuit on the board does separate the component sync from the component video, and the JPAC does the same for the PC output"
here: http://www.aussiearcade.com/archive/index.php/t-11311.html
« Last Edit: September 05, 2017, 01:18:31 pm by bimm25e »

bimm25e

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Re: Making a RGB scart cable for a JPAC
« Reply #7 on: September 05, 2017, 05:20:52 pm »
yeah i am trying to send c-vid from the SCART down the h-sync line on the VGA port on the jpac and its just not syncing -

 oddly enough, im using a ps3, and when im  on the menu, if i select the photos menu, the background turns blue and the screen actually syncs, but then when I move the menu or open a game, the sync is unobtainable.

Its too bad that one site looks like it suggests the jpac can separate c-sync from c-video if you remove all the jumpers (15, 15, 31 khz) but its certainly not working for me

buttersoft

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Re: Making a RGB scart cable for a JPAC
« Reply #8 on: September 05, 2017, 09:54:55 pm »
How do you know using c-sync instead of h-sync won't work?

Either way, my recommendation is still that you talk to Andy from Ultimarc. He has a great rep for supporting the stuff he makes.

bimm25e

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Re: Making a RGB scart cable for a JPAC
« Reply #9 on: September 06, 2017, 01:19:19 am »
So, some news. Connecting the scart from the ps3 to this thing:
http://m.ebay.com/itm/PCB-Advance-JAMMA-To-Scart-RGB-adapter-Retroelectronik-/152243258281

Gives me un synced video on the screen. Attaching a lead from the comp vid scart pin to the jamma video sync pin gives me synched video!!!!  But the sync isn't great, you can tell the monitor is getting jittery as a result of the video not being separated from the sync. It works really well but I'm still going to look into a sync separating circuit to get a perfect picture :D
« Last Edit: September 06, 2017, 11:54:20 am by bimm25e »

bimm25e

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Re: Making a RGB scart cable for a JPAC
« Reply #10 on: September 06, 2017, 11:07:20 am »
found this site, sells premade sync se4parators:

http://www.jamma-nation-x.com/jammax/store.html


unfortunately, they are sold out of the JNX EL4583 Sync Separator (the one I wanted!!!!) anyone have schematics to make one?

bimm25e

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Re: Making a RGB scart cable for a JPAC
« Reply #11 on: September 06, 2017, 02:36:24 pm »
More info here:


http://remy.baligant.net/extracteur.htm


I am ordering the parts from his parts list, and plan on buliding the circuit, not sure what to do for the project board though, I'd need one that can fit a vga and scart port

  
 

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