Author Topic: S-Video (y/c) to RGB converter circuit  (Read 3605 times)

Offline Hojo_Norem

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S-Video (y/c) to RGB converter circuit
« on: July 13, 2005, 07:37:46 am »
My PSone LCD arrived not to long ago.  The composite picture from my c64 isn't to bad, however I realy would like to be able to use the 64's Y/C output, however the PSone lcd dosen't do S-video so obviously I need a s-video to rgb converter circuit.

However google has pratically failed me on this one, the closest I can get after waiding thurgh all thew rgb to s-video links is a single site showing a NTSC to VGA converter.

However I have found a chip that might do the job, the tda3565 pdf datasheet, but looking at that just shows up my lack of electronic smarts.

Can anybody with more smarts help me out here, or shall I just bite the bullet and stick with composite?

 
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Offline Adeptus

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S-Video (y/c) to RGB converter circuit
« Reply #1 on: July 13, 2005, 11:07:30 am »
Are you using a real C64 or one of the new C64DTV's?

Offline Hojo_Norem

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S-Video (y/c) to RGB converter circuit
« Reply #2 on: July 14, 2005, 01:09:40 am »
Im testing with a real C64 for now (one that has both composite and Y/C output) but I will be using the new C64 DTV when its released.  It can be hacked to output Y/C.
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Offline emuman100

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S-Video (y/c) to RGB converter circuit
« Reply #3 on: July 14, 2005, 03:31:16 pm »
That IC will work, but you'll need lots of supporting circuitry as listed in the application schematic. It won't be as simple as an LM1881. Plus, that'll only accept a PAL signal, not NTSC.

Offline Hojo_Norem

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S-Video (y/c) to RGB converter circuit
« Reply #4 on: July 15, 2005, 02:59:02 am »
I understand that it isn't a easy solution but so far its the only viable one that I have found.

About it being PAL only, no probs, I live in PAL land anyway (and the PAL PSone LCD don't do NTSC or 60Hz either).

Anyway, It seem sthat the only real problem with the chip is the need for a "sandcastle" pulse.
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viletim!

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S-Video (y/c) to RGB converter circuit
« Reply #5 on: July 15, 2005, 05:27:35 pm »
butter_pat_head,

The IC you mention is a TV chip. It takes Y, C and sandcastle and spits out RGB which goes to the three cathode drive transistors. This RGB signal isn't going to come out ready to feed a monitor, it'll need attenuating + buffering first.

The sandcastle pulse is a 3 level pulse that contains back level and colour burst timing information. You can get those timing signals with a LM1881 and combine them with some transistors or cmos gates to make the sandcastle.

You'll need access to an oscilloscope to tweak the circuit and get it working properly. It'll be very difficult without one.

Honestly, I think you're better off with a more modern IC. The TDA3565 is 20 years old and there are much better devices on the market now. Have a look at the latest offerings from Philips or perhaps Sony. The CXA1585Q seems to be just what you're after - Y/C in (can strip sync off Y or external), RGB (75ohm 0.7Vpp) out, low power consumption.

Offline Hojo_Norem

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S-Video (y/c) to RGB converter circuit
« Reply #6 on: July 16, 2005, 07:41:27 am »
Thanks for that.  Anyway I struck upon another idea.  I started googling info for every one of the bigger ICs and I discovered that the heart of the LCD is the AN2526NFH which has the job of converting the RGB from the PSX connector and the composite from the AV jack into something that the pannel understands.

Just my luck that this chip will accept Y/C aswell!  I have done a peliminary hack to get s-video on the screen and it seems to work but thene now seems to be a slight amount flicker but I think that because I replaced a surface mount capacitor with a disc type from my bits box.

If I get satisfactory results from this then Il try to write some kind of guide, but I can't see myself at being any good at it! ^_^
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viletim!

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S-Video (y/c) to RGB converter circuit
« Reply #7 on: July 16, 2005, 04:55:30 pm »
butter_pat_head,
Good idea. From the app notes it looks to be fairly straight forward. Don't forget to terminate both Y and C with a 75 ohm resistor...