Can anyone ID this A1200 s-video mod?

[AmigaJules]

Hi Folks,

I got this A1200 yesterday. Someone's modded in s-video and a pal/ntsc switch.

Can anyone ID this s-video circuit? The output is pretty wavy on my LCD display.

Wondering if there's a better circuit to use, or if I can make this one better by finding a better ground than the RF shield around the composite connector (it's pretty oxidized and if the lid isn't soldered - it doesn't appear to be - I imagine the connection isn't as good as it could be).

Also, does anyone know what the capacitor on one of the gayle pins is for?

Lastly, can anyone ID the motherboard revision? The motherboard says Rev 1D. The budgie is 391425-01 Rev 0. I can't find E123 or E125 anywhere on the board. R118 is missing (just the solder pads are there).

[alexh]

It looks like it takes the S-Video from the A1200's onboard Video Encoder and then amplifies(?) it.

[rkauer]

Yes, that's securely is a S-VHS (Y-C) mod.

The capacitor is a (badly implemented) CC_Reset fix.

E123 & E125 are in the underside of the board (and I bet it is a 1D1 revision). The mobo have a green wire running vertically in the middle?

[AmigaJules]

Thanks both for your input

Originally Posted by rkauer

The capacitor is a (badly implemented) CC_Reset fix.

E123 & E125 are in the underside of the board (and I bet it is a 1D1 revision). The mobo have a green wire running vertically in the middle?

By "badly implemented" do you mean poor soldering job? Or that there's a better fix for the issue?

It has a yellow wire running from a pin on the budgie chip down to an IC next to the alice chip & a smd resistor. You can see it in the 2nd pic.

Looking at fixes, artwork, schematic & part numbers, I've come to the same conclusion: probably 1D1.

I've also found (I think) the schematic for the svideo mod: http://www.ppa.pl/artykuly/pics/sekc...eo/schemat.png - unfortunately, I don't read polish

The part numbers on the transistors match. Looks like my mod is missing a couple of capacitors (c2 & c4) on the ground lines as well as the ferrite beads.

[a_petri]

Originally Posted by AmigaJules

Thanks both for your input



By "badly implemented" do you mean poor soldering job? Or that there's a better fix for the issue?

Probably both.

A capacitor between CC_RESET and Vcc (as described in http://aminet.net/docs/hard/A1200-ccreset.txt ) is a poor substitute - it only fixes the "PCMCIA network card does not work if plugged in while power on" half of the problem (hopefully), but not the "PCMCIA network card does not work after Ctrl-Amiga-Amiga" half.

A proper CC_RESET hardware fix should place an inverter between /RESET (active-low reset signal for the A1200 motherboard) and CC_RESET (active-high reset signal for the PCMCIA card) signals. This needs a transistor and two resistors (e.g. http://www.faime.demon.co.uk/retro/i...00.schem.1.gif ).

But there is a purely software-based solution to the CC_RESET problem: http://aminet.net/util/boot/CardReset.lha

[Zetr0]

Over all not a bad bit of home made hackery

I love the Svideo Y/C amplifyer mod, personally I would of removed the RF and or the Composhite *ahem, I mean composite out and plumbed for simple SVideo.

The CC reset looks like a quick fix to be honest and for 50% of the job done, arguably its possible that the person whom moded it for the reset may of only known about the primary fix and when the software reset was place into the public domain there was no need to upgrade it.

(personall I love my soldering too much not to do a full fix )

[rkauer]

Originally Posted by AmigaJules

Thanks both for your input

By "badly implemented" do you mean poor soldering job? Or that there's a better fix for the issue?

A way better way to fix the problem is using a transistor and a pair of resistors. IIRC, the proper fix is inside the CNET.device package (as a schematic).