Trying to wrap my head around why a particular CVBS/SVideo to VGA converter I have accepts every composite signal I feed into it, but refuses a C64C CVBS signal (which my 55" Samsung TV doesn't seem to have a problem with). Here's a capture that works (from a Timex Computer):

And here's the one from the C64:

One thing that seems evident is that the voltage amplitude of the Spectrum clone is about half of that of the C64. I've tried a series resistor to no avail. Any ideas?

Some more info here, as I have the C64C, it outputs Luma and Chroma in separate channels. I tried to make an adapter for SVideo, but I'm still out of luck. Here's a sample of the chroma channel:

And the Luma channel:

Could it be that the upscaler doesn't receive enough current from these? I'm thinking in trying to boost the signal with something like this:

Meanwhile, I ordered a different upscaler. I still wanted to see if I could solve this somehow, as an academic exercise :)

Here are a couple more of waveforms, with the CVBS of the TC2048 (blue) and the C64C (yellow) side-by-side. First, the Horizontal Blank:

And the Vertical Blank:

A couple more detailed waveform on each Vertical Blank: