What's new
By:
Filters

Fitting VGA and standard-def YPbPr/component - was: 15khz to 30khz sync converter circuit

N

numbski

Student
Joined
Jun 22, 2016
Messages
66
Reaction score
4
I swore I wouldn't mess with this, but the more I thought about it, the more likely it seemed that if I wired a VGA plug onto my CPS2 that I would wind up trying to hook it to a display that couldn't sync down to 15khz.

So I'm bookmarking this for later. I will certainly wind up coming back to it. If I'm going to go to the trouble of wiring the plug, might as well convert the sync while I'm at it.

https://www.maximintegrated.com/en/app-notes/index.mvp/id/3327
 
Might as well do them all. A pair of LM308 op-amps will convert RGBS to YPbPr, so I will try that too.

Also plan to wire a sync separator on the VGA plug, providing composite and vertical sync (apparently you don't have to clean horizontal sync?):

http://www.ti.com/lit/ds/symlink/lm1881.pdf

*sigh*

Always getting in over my head.
 
Last edited:
For splitting vsync from hsync for the VGA mod:

http://www.ti.com/lit/ds/symlink/lm1881.pdf

Went shopping today, and I am still relatively new at electronics. That dual op-amp circuit for converting RGB to YPbPr - it has some awfully specific resistor values!

107ohm
549ohm
2940ohm

Not entirely sure how to provide those without just getting pots and turning them to the right values and then hot glue them to fix it.
 
Right or wrong, I am going to use the pots+hot glue method. If that happens to work, I can run down the "right" way to deal with it.

Just got looking at the Open Source Scan Converter project. If this doesn't work as planned, that might be a route I can go - incorporate pieces of that.
 
numbski said:
it has some awfully specific resistor values!

107ohm
549ohm
2940ohm

Not entirely sure how to provide those without just getting pots and turning them to the right values and then hot glue them to fix it.
Click to expand...
if you place resistors in series you can add the values.
http://physics.bu.edu/py106/notes/Circuits.html

So for 107 ohm you could place a 100ohm and a 6.8ohm in series for 106.8 ohm, if you truly need it to be that precise (ie: a 110 ohm is not exact enough) then pots are likely the way to go since even if you run the right value resistors they're still going to be off by up to 5% (so a 100ohm resistor might actually be as low as 95 or as high as 105), unless you special order high tolerance resistors.
 
You must log in or register to reply here.
Back
Top