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

[![enter image description here][1]][1]

And here's the one from the C64:

[![enter image description here][2]][2]

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?

  [1]: https://i.sstatic.net/vax0E.png
  [2]: https://i.sstatic.net/rndVD.png