A couple of months ago i’ve built an OSSC for a fellow forum member. At first it worked pretty well on his Micomsoft SC-512, while feeding the component output of his PSP or his PS2 into the OSSC. But then some strange behaviour started: the OSSC still worked on his TV, but the SC-512 refused to recognize the HDMI output of the OSSC. Some forum members assumed a faulty SC-512 – but the SC-512 still worked flawlessly with another (borrowed) OSSC.
So he sent me the faulty OSSC and i did some testing on my TV (without the capture card involved). I recognized some crawling pink dots in the black area of the test pattern:
… which were all over the screen in pass-through mode with my PAL SNES (while only occasional visible in 2x and higher output modes) and a flickering output in 4x mode.
So i resoldered all the pins of the FPGA, the IT6613 and the HDMI connector -> without any changes. Then i replaced the IT6613… and that did the trick. The pink dots were gone and the 4x output was stable. The IT6613 was obviously broken.
I sent the OSSC back to him, hoping his capturing issues with the SC-512 are gone too. But sadly they got only stranger. He did some testing and wrote the following about the results:
1. OSSC directly to the monitor -> with the PSP via YPbPr connected, NO PROBLEMS
2. OSSC directly to the monitor -> PS1 games with the PS2 via YPbPr, NO PROBLEMS
3. unplugged everything and inserted capture card into the signal chain
4. OSSC with the PSP connected via YPbPr (test pattern):
5. switched to YPbPr input (to the picture the PSP is outputting):
6. turned everything off and connected the PS2 (instead the PSP) to the component input of the OSSC and turn everything on (test pattern):
7. switched to YPbPr input -> NO PROBLEM
One day later he tried again – now the picture from the PSP seems fine too:
… for now!
So he is confused… and me too. How can any connected analogue video device influence the test pattern? What could be broken too? Is it possible the SC-512 or the component output of the PSP (in some way) have done some harm to the OSSC?