AV to VGA adapter..

desiv · Posted: Mon Nov 02, 2009 5:18 pm Post subject: AV to VGA adapter..

Just a quick heads up. I just bought this little adapter for converting AV to VGA so I can display on my computer monitor.
Now, this is NOT a flicker fixer per se. It does not take an RGB connection from the Amiga and convert it bit for bit to the VGA monitor.

It has 3 inputs, a VGA (for passthru I believe), a composite and an s-video.

I don't yet have s-video on my Amiga, so I am using my A520 to output composite. And so far, I'm impressed. It's not bad.

I'll be interested to try it if I can manage to tweak my A520 for s-video.

Here's a link:
http://i1014.photobucket.com/albums/af261/villaesc/Amiga/av-vga_1.jpg

So, why would you want to do this over a vastly superior flicker fixer?

It was $40 shipped. Smile

I did have to rip apart the power adapter, since it came 220. The adapter supports 100-240, so I ripped out the weird plug and added a regular plug and it worked great. I didn't have a 5V correct amperage and plug adapter handy.

It says it support PAL and NTSC.
I can do PAL from my NTSC Amiga, but it's monochrome. I think that's the A520 tho. At least I can. When I tried it before on my LCD TV, I just got "not supported frequency".

The big question I think will be, how will it last? Can I leave it on for hours and hours? Will it survive more than a few weeks/months? Who knows...

I'll probably try pumping the Amiga RGB into the VGA port on it, just to see what it does, but I'd be shocked if it took 15khz RGB on that port.

desiv

marquisor · Posted: Wed Nov 04, 2009 5:30 pm Post subject:

hi! as from chitchat:

SVHS pins are http://en.wikipedia.org/wiki/S-Video

Pin 1 GND Ground (Y)
Pin 2 GND Ground (C)
Pin 3 Y Intensity (Luminance)
Pin 4 C Color (Chrominance)

Amiga monochrome on A500 should be Luminance only, so connect that to Pin 1/3. Pay attention on what is GND and what is Y-Signal Smile

As for Chrominance i guess you could get the color information out of the Amiga RGB Output. Here's a picture: http://666kb.com/i/bdtrlcobbfjqkke5w.jpg
It's german, but for this purpose you recognize what is what Smile

So for Chrominance i would twirl the analog RGB signal (RGB output 3,4,5) to ONE cable and connect it to Pin 4 of SVHS. Get some ground (maybe 2 or 3) from RGB out 16-20.

You might get Luminance out of Pin 10 from RGB out, too, but i'm not sure.

Maybe this works, dunno!

Regards

EDIT: i read something about you could get the signals directly out of the chipset, no complex A520 mod is required. some guy (he's television technician) did this once with a CD32 as written in a german forum. he's a member of http://www.cbm-museum-wuppertal.com/

another hint:
maybe wiring RGB together could produce a shortage!! so first i would try only with ONE signal red, green or blue together with the Pin 10 from RGB or the monochrome from the RCA/cinch.
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A4000D A3640 22MB/10GB/DVDRAM Connexion (A2065) LAN Ext. FliFi/SD
A1200D Apollo 1230 68030@25 10MB/4GB PCMCIA (CNet) LAN

marquisor · Posted: Wed Nov 04, 2009 8:08 pm Post subject:

i've found another thing:

http://www.amigamaniac.com/RGB_to_PAL_NTSC_adapter.html

but that guy sits in australia Wink

it seems he used only pins 3,4,5 (RGB analog, as i suggested) and 11,12 (HSYNC/VSYNC, dunno why yet)

EDIT:

AND ANOTHER THING:

http://www.analog.com/static/imported-files/data_sheets/AD724.pdf
with these schematics it should be easy to build one adapter from scratch for an electronics geek ;D
_________________
A4000D A3640 22MB/10GB/DVDRAM Connexion (A2065) LAN Ext. FliFi/SD
A1200D Apollo 1230 68030@25 10MB/4GB PCMCIA (CNet) LAN

desiv · Posted: Wed Nov 11, 2009 3:45 am Post subject:

Well, I got some diodes and a resistor and cap and SVideo plug and I think I'm going to try the s-video mod on my A520.

Interesting thing. I opened up the 520, and it's... let's say.. it's had work done.

Some obvious soldering spots and missing solder (on the spots where the casing would be soldered to the board in a few spots.)...

Interesting.

It works in composite, so apparently they must have fixed it from whatever, but...

We'll see if I can break it some more... Smile

desiv

The amigamaniac board is supposed to be really nice, but I missed the last run and he doesn't have any plans for any more right now. Oh well.

Shmup Jockey · Posted: Wed Nov 11, 2009 6:44 am Post subject:

This is all way, way over my head, but I thought I'd say: 'Good going, Desiv!' and 'Keep us updated on your results!'

I've stumbled across most of these links in the start of my eternal quest to NTSC/PAL switch my Amiga.

I wish I could offer more than encouragement, but this hardware stuff is far beyond my capabilities...and barely within my realm of understanding.
_________________
Some of the best shmups have been on the Amiga: Apidya, Disposable Hero, Project-X, and so on. Simply amazing...

desiv · Posted: Wed Nov 11, 2009 8:36 am Post subject:

Well, no luck so far.
I think I have my soldering right (looks good), but when I connected it, it was white and green lines only...

Interesting, when I accidentally touched the s-video ground wire to the luma connected wires (so it wasn't grounded to the A520 at all), I got a monochrome screen. Not as sharp as the regular mono connector tho.

When I then grounded the other ground wire, the mono pic got a bit better.

Still no color tho.

The instructions were a bit iffy.

The instructions I found for a PAL s-video fix were very good, but they mentioned NTSC looked different.

The instructions for NTSC are very different.

Hmmm...

I might go with the ad724 option. It's the same basic method Amigamaniac in Aus used, and I seem to remember there were some good schematics on EAB for it...

Good news is, I didn't fry my A520, so I still have composite color. Smile

Oh well... It's late, so I better stop..

desiv

desiv · Posted: Wed Nov 11, 2009 5:47 pm Post subject:

Ok, I had a new theory while sleeping last night.
Confused

Ok, I also thought about my adapter. Smile

I know that someone did some work in there before. Replaced a chip at least, and several grounds looks hmmm.. interestingly soldered.

Since I was kind of getting a monochrome pic if I connected the adapter (not the 520, but the svideo-vga adapter) svideo ground to the luma (which I still think is weird), I think I'll try soldering a wire to pin 20, which is the Amiga video ground, and bring it all the way over to my plug and see what happens then.

Not now tho, but sometime today.. Smile

desiv

marquisor · Posted: Fri Nov 13, 2009 12:37 am Post subject:

what s-video vga adapter do you have there??

did you try my description yet?
_________________
A4000D A3640 22MB/10GB/DVDRAM Connexion (A2065) LAN Ext. FliFi/SD
A1200D Apollo 1230 68030@25 10MB/4GB PCMCIA (CNet) LAN

desiv · Posted: Fri Nov 13, 2009 3:35 am Post subject:

desiv · Posted: Fri Nov 13, 2009 3:46 am Post subject:

Yep, just tested my grounds and pin 20 (along with all the other grounds) are connected to where I was grounding it.

It's not my solders. I checked.

It could be the A520. It works enough for Composite, but maybe not for s-video. I say this because it's had work done, and it looks like my quality work. Wink

At least 1 chip was replaced, and my hack uses 2 pins from that chip. Maybe they replaced it with a similar, but slightly different chip?

Or, it could be that the hack doesn't work. Either it's got a problem, which I doubt, or maybe there are more than 1 release of the NTSC A520.
I do wonder tho, because the PAL hack was MUCH more involved than the NTSC hack...

It's also possible that I have the wrong parts (diodes, resistors, cap).
Well, probably not that cap, as the cap is on the color (chroma) and I couldn't even get luma working properly.

Oh well....

desiv