Getting split horizontal screens in Forced VGA mode

Starwindz

New member
Greetings,
I'm currently getting split horizontal screens when in Forced VGA mode at 1080P.
All my solder joints look correct and I've checked continuity for any bridges.
I've read a few forum posts you've replied to that mentioned to check pins 6/7 to make sure they have continuity to the pads where the resisters that were removed are. Pins 6/7 are making good contact but I can't seem to get continuity where the open hole pads are, I even removed the solder and resoldered that area a couple times to make sure the joints were making contact.
I do notice my flex cable is different than the ones in your instructional (JP 1 step is not needed?).
I've ordered another flex cable just to be safe but can you recommend anything else I can try in the meantime?
Thanks!

DCHMDI Loading Screen.png
DCHDMI Test Screen.png
 

citrus3000psi

Administrator
Staff member
What do you mean you don't get continuity? You need to make sure you have continuity between pins 6/7 on the analog output to the flex cable.

If you have a VGA box, plugging it in will likely solve the problem temporarily.
 

Starwindz

New member
Thanks for the reply back.

I believe it was mentioned here that you need continuity between pins 6/7 to the open hole pads: https://www.reddit.com/r/dreamcast/comments/c7ipj1
Plugging in a VA box does temporarily fix the issue, but does this mean I'm getting a lower resolution signal on my HDMI port?

Where can I find the analog output on the flex cable?

Thanks for the assistance.
 

citrus3000psi

Administrator
Staff member
No, plugging in the VGA box, forces the internal GPU to send out a 480p pixel bus. When you do ForceVGA in the DCDigital it simulates plugging a vga box in and expects the 480p signal. This is why you are seeing a split screen, because the console is not outputting 480p internally.

You removed two resistors on the DC board and then soldered two holes over those resistor pads. Those holes are the connection to PINS 6/7 on the analog port.
 

valterb

New member
I'm having the same problem. I've reflowed those two points multiple times, checked continuity to the AV port, and cleaned and reseated the connector end of the ribbon cable. I don't have a VGA box to test with, but all the other connections look good according to the test screen. Is there anything else I can do to troubleshoot?

EDIT: I forgot to mention that composite no longer works with "Force VGA" enabled. That means at least one of the two pins (6 or 7) is being grounded, right?

EDIT2: I noticed that there's only one conductor going from R1 and R2 back to the DCDigital board. Since there's continuity to the AV connector, and since I checked continuity from R1 and R2 on the ribbon cable to the vias near the CPU, the only explanation I can think of is a bad D1 on the ribbon cable?

EDIT3: Aha! D1 was the problem after all. It wasn't making a good connection on the C1 side. Reflowing the solder there fixed the problem entirely. Thanks for letting me use your forums as a rubber duck ;)
 
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