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?