Glad you are making progress with this :-) Yeah I'm not sure about Blank either. Like you said, the timing could be off by using the Back Porch signal. I've noticed that the BT9101 and BT9103 both use Blank signal. I will try and trace my BT903 Blank pin to the CLIO chip. Hopefully the same pin on VA536 motherboards will provide an active Blank signal.
Do you have a picture of the RGB mod chip you found? It sounds like they might have used a BU3616K chip which is about the same size as the ADV1725 but simpler in design and application.
I have a PDF of the pinouts for the VPA536, blanking and sync is mixed internally. The only output being H/V sync. Blanking being applied to Luma and Composite out. That's why I was thinking of stripping blanking from there. But the back porch should suffice.
No I don't have a picture. It had to be something on the lines of 24 bit dac with lm1881 im certain of that.
So reading this: http://www.edaboard....ead139994.html
makes me think this design will work as is.
I'm not even sure blanking is a relevant thing on newer CRTS with sync present and I am almost certain blanking isn't needed for LCD TVs.
I suppose using any 24 bit, 3 channel video DAC with a lm1881 combo is certain to lead to success. The ADV7125 was just more readily available.
Or even using 3x 8 bit video DACs.
I am probably going to do two solder jumpers here. One to lock blank to the lm1881 back porch and one to lock blank high (as in no blanking). I'd think it would be good to do the same on any similar designs you come up with. The lm1881 also puts out Vsync. I think you can use Csync (as Hsync) and Vsync as is to put out to VGA although I am not certain about that.
Let me rebuild this board for hopefully the last time.
Just occurred to me I never had the LQFP-48 package size for the ADV7125 even correctly ported.
Edited by the_crayon_king, Sun Sep 24, 2017 2:20 PM.