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Author Topic: Question about combining H Sync and V Sync  (Read 890 times)

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mrchrister

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Question about combining H Sync and V Sync
« on: November 30, 2019, 04:03:35 pm »
Hey guys,

I'm planning of creating a cable to connect a PVM 2030 to my Radeon card running CRT Emudriver.

I found the pinout map:

Connection HDDB15F DB25F
Red 1 6
Green 2 5
Blue 3 4
H-sync 13 3*
V-sync 14 3*
Ground 15-24 (any) 6, 7, 8, 10


I don't have a lot of experience but own a soldering iron and want to learn something new.

So I want to order:
- Db25 breakout solder terminals
- Vga cable
- Multimeter

My plan of action is cut the vga cable, strip the shielding of the rgb wires, identify the different cables with multimeter, and solder to Db25 terminal.

My question would be what to do for Composite Sync? I'm hoping to just connect H sync to the DB25 connector and use Emudrivers C Sync feature (not using v Sync at all). Would I need any resistors in this case?

Alternative would be to create a circuit like the one attached but I'm not sure if soldering a circuit board is something I feel comfortable of tackling.

Arroyo

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Re: Question about combining H Sync and V Sync
« Reply #1 on: November 30, 2019, 10:55:09 pm »
Keep it simple and order one of these:

https://www.amazon.com/dp/B01FNALYLA/ref=cm_sw_r_sms_c_api_i_6IZ4DbZZ3PYEQ

Just connect it to the horizontal and use C-Sync output.  If you are having trouble you can order one of these:

https://www.amazon.com/dp/B00WFZRNMQ/ref=cm_sw_r_sms_apip_18xGrWQVDmzUi

And use the Horizontal and Vertical combined for Sync to check things out WITHOUT C-Sync enabled.

mrchrister

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Re: Question about combining H Sync and V Sync
« Reply #2 on: December 01, 2019, 09:03:48 am »
Thanks for your help! I wish I could keep it simple but the PVM 2030 uses a DB 25 plug for RGB input instead of standard BNC connectors. I bought all components to create the cable and will work on this today.

Arroyo

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Re: Question about combining H Sync and V Sync
« Reply #3 on: December 01, 2019, 09:10:05 am »
Ah yes, you are right!  I forgot about those models.  Yeah you are on the right path.  No resistors needed for using the H wire, just enable C-Sync. 

buttersoft

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Re: Question about combining H Sync and V Sync
« Reply #4 on: December 01, 2019, 05:48:18 pm »
As Aroyo says, go the C-sync route first. This should work perfectly for 240p content, and might also work perfectly for 480i/576i content.

Sometimes those old Sony's get a bit flickery with interlaced modes depending on how sync is combined, and at what levels. I have a few 2730's, and those are using a resistor in each sync line, them combining, to get the best results. IF you want to try this, start with a 500R resistor and a 1k pot in each sync line, then merge into another 1k pot, then feed into the set's sync pin. Leave the last pot at zero and dial the other two around and watch what happens to the flicker. If this works, add 1k resistors in front of the pots, and go again. I'm suing between 2-3k in each horizontal sync line, and then about 4-6K in each vertical, then about 1K on the combined line.

This makes the image much more stable for me. It's still interlaced, but the flicker is minimised. My PVM-2730's are PAL models, so they will decode NTSC fine, but the circuitry works and looks best at 50Hz. Yours may differ. I can also use the Extron 190F i have and get just as nice a picture, but i only have one of those. Using Viletim's N64RGB mod, however, is instant headache city. The picture jumps around so much it's not watchable. I know Tim is a genius, so the sync must be perfectly within standard, it's just not giving perfect results in this case.

Zebra

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Re: Question about combining H Sync and V Sync
« Reply #5 on: December 05, 2019, 08:37:28 pm »
You can get DB15 breakout boards on ebay with numbered screw terminals. It will save a lot of effort on identifying which line is which. You can also get DB25 breakout boards with screw terminal which will save a lot of very frustrating soldering of tiny close together pins.

If you go with the VGA to BNC cable, you can just snip the BNC connectors off the end and attach to your DB25 breakout board. You will probably get better results this way than a diy job unless you understand how to properly ground an rgb cable.

I recommend picking up an Extron RGB interface of eBay. They're cheap and in addition to solving all sync type issues, they give you an lcd display showing your resolution and refresh so you can double check groovymame is work as it should.

mrchrister

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Re: Question about combining H Sync and V Sync
« Reply #6 on: December 17, 2019, 03:23:37 pm »
Thanks for the recommendations guys. I ended up soldering h sync and not connecting v Sync at all. Activating c sync in CRT Emudriver works perfectly and I'm very happy with the picture I'm getting :)

I also recently got a MISTer which can activate c sync through VGA as well. Results have been awesome. Played some Genesis yesterday and really loving it!

Btw, yes interlaced is flickery but I'm not planning on running much interlaced content on here. I tried Dragon's lair and didn't notice the flicker but yeah, windows looks very flickery on it.
« Last Edit: December 17, 2019, 03:30:20 pm by mrchrister »