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Amiga computer related discussion => Amiga Marketplace => Topic started by: Gulliver on July 31, 2007, 12:54:12 AM

Title: Obtaining SVHS output from an A1200
Post by: Gulliver on July 31, 2007, 12:54:12 AM

i was reading the A1200 schematics and found this

From the Sony video encoder chip(CXA1145), U12:
Pin 15 is chroma out
Pin 16 is luma out

so could it be possible to simply wire the apropiate conector and get SVHS straight away, or do i need to add some circuitry?

Thanks in advance

Title: Re: Obtaining SVHS output from an A1200
Post by: narmi on July 31, 2007, 01:57:51 AM

According to a post by Jope at the EAB (http://eab.abime.net/showthread.php?t=30752&highlight=s-video) (scroll down to post #4), the correct schematic for the s-video output is in the CD32 schematic.  I haven't seen it, but you probably need a capacitor for each signal, and possibly a resistor.  My external adaptor (in the linked thread) uses a 220uF cap and a 75-ohm resistor connected in series.

BTW, it's s-video, not SVHS.  SVHS is something different from, but often confused with s-video.

Title: Re: Obtaining SVHS output from an A1200
Post by: Gulliver on July 31, 2007, 02:22:54 AM

Thanks for your reply. Anyway i have just seen cd32 schematics, and are a little complicated, needing some transistors and diodes. I was hoping there was a simpler design for electronic newbies, with easy to get components. By the way my cd32 schematics suck for reading, they do not have enough detail!
On the other hand your adaptor is way too cool, simple, but then NTSC for my PAL soul.
According to that post you quote it should be easy to do the conversion, the clock part is easy for me, but then when putting STND pin to ground should i cut all other connections coming out from STND? I am sorry i dont get this part!

PS: Sorry you are right it was s-video

Title: Re: Obtaining SVHS output from an A1200
Post by: vic20owner on July 31, 2007, 04:24:36 AM

I installed S-Video into my A1200 using the neobitz s-video board.  Just google it.

Title: Re: Obtaining SVHS output from an A1200
Post by: narmi on July 31, 2007, 04:34:41 AM

I found the CD32 schematic, and the circuit is more complicated than I expected.  The transistors look like they are buffers for the signal, which could mean that the Sony chip cannot source much current.

I would try connecting a 100uF capacitor and 75-ohm resistor in series, along with a 100pF capacitor connected to ground.  This is the part of the circuit to the right of the transistors, from what I can tell (the image is not very clear).  Trying to make the adapter I made for PAL use is much more complicated than this.  I made it for my A500 and A1000 which don't have this type of circuitry.

Has anybody else here made this mod to their A1200?

EDIT: My adaptor is based on the Neobitz adaptor, which is also NTSC only.  However, if you order that kit, it would be easy to modify the board for PAL use.  Just change the crystal to one with the correct PAL frequency, and change the logic level on the STND line.

Title: Re: Obtaining SVHS output from an A1200
Post by: Chain on July 31, 2007, 05:56:22 AM

Svideo form pal A1200 on our site

http://amiga.probers.info/index.php?option=com_content&task=view&id=1370&Itemid=206