VGA box question (with rewarding picture)

[ILAMtitan]

I finnished up my snes mods a few months ago, and i recently found the VGA box for the dreamcast through hack a day. I knew they existed but never realy looked into em. Since i started looking for more information i stumbled accros many projects and mods, most of wich will probably be made into my dreamcast. I just have to steal it back from my brother now.

I just had a question for those of you who made the vga box, what ratings did you use for the signal and ground isolation caps (volatage), and what diodes where used for the horzontal and vertical ground refrence points? I was just going to use 1/4W resistors, if thats a problem (which i dont think it is) please tell me.

And for your time, my snes.
more of my recent projects here: http://flickr.com/photos/bbasile/sets/1085901/

[ptr.exe]

I used 220uF 10V for the RGB caps, but ive used 16V in others that worked okay. I wrote a tutorial in the dcemu.co.uk forums that may be useful to you.

[Cyphix]

Very nice SNES. The black and white fit it well.

[Nemesis]

I <3 your clock, is there a tutorial on how to make one anywhere?

[ILAMtitan]

sorry it took so long to reply, best buy has my computer right now. Thanks for the info about the VGA box. As for the clock, start here: http://www.electricstuff.co.uk/nixclock.html. He has all the info you realy need.

[Nemesis]

thanks a bunch!

[ILAMtitan]

I had another question for those who have made the VGA boxes. THe schematic on devcast has a 74HCT244; and as far as i can tell it just processes the horzontal and vertical synchronization signals. I saw another that forwent the IC entirely. Is the IC needed, and is there any benifit/loss from its usage?

[Nemesis]

the thing is u don't really need the ic chip here ptr.exe made a more simple circuit/guide, this is the one i'm going to do, mostly because it's smaller...

[ILAMtitan]

This is probably another stupid question (especialy coming from someone who is studying to be an electrical engineer) but all the caps i canabalized are electrolytic and the schematics dont mention polarity; does it matter? Ive noticed in pictures of other vga boxes that they use the same kind of caps, but they never mrntion the orientation.

[semicolo]

since the monitor is a receiver and the dreamcast the emitter, you'd better tie the + to the dreamcasts side.

[ILAMtitan]

I finaly got all my parts in for my VGA box, got it built, but when i connect it to my monitor andpower up, all i get its a black screen. I had the caps like semicolo said and it just flashed the noinput sign,and then switched the polarity and then it was jsut blank. ANyone encounter a simminarl problem in the past that can help?

[semicolo]

Did you use a chip for the synchronisation lines ? If no, maybe it'd be needed, ptr.exe could answer that, I did a vga box with the chip and it worked, never tried without it.

[ILAMtitan]

I used ptr.exe's schematic, since im kinda on a budget here.

[ILAMtitan]

OK, i think i may have royaly screwed my DC. I tried to use it on my buddys TV (since i dont have one) and it would stop putting out video after the swirrly logo at the begining. Seamed to work and put sound, then it just quits. ANy ideas whats wrong, or do i need a new dreamcast.

[Matt]

If it outputs the swirly thing the chip can't be crushed. Odd. Most probably a disk error, try it with different games

[ILAMtitan]

When i boot with a game it just displays the logo like normal, goes to the set time page, and then goes black. SO i dont think its the disk. I might of not put the shield back in right and its over heating, but i havent take much of a better look at it yet.

[ILAMtitan]

Sorry to keep posting, but it works again. I just took out my VGA box and the video worked once again. I have no idea what was wrong, but i assume that i had put the thing togther wrong or something wasnt fitting right due to the added ribbon cable.

[Lexus_the_Great]

Just for the record, I just finished my Internal VGA Mod using the diagram by ptr.exe (without the IC) and it works just fine. If anybody else wants to make it here are the things I used:

For the caps I used 16V 220uF caps, 4.7K and 150 Ohm resistors. I just used 2 normal diodes.

Some pointers (and DOH's from me ^^):

If u use a VGA conector wich is fitted through the top half of the dc, make sure it is in place before you solder it to your circuit ( ). (same with the switch)

For the switch, ptr.exe's diagram does not show that the 2 "VGA selects" should NOT be solder together (as in the diagram), if they connect VGA mode is engaged, so if you solder them together your normal AV out will not work, even if you flip the swith.

Make sure u solder the wires to the right points on the mainboard! Just as prt.exe I soldered it on the back but I ( again) misplaced two wires because I counted wrong! Check Check and Check again!