[ppppenguin]

old_tv_nut has got this right. A lot of older video generating devices produced a non-standard waveform. For example I have a TV test pattern generator c1970, from a reputable manufacturer, that gives PAL colour bars, crosshatch and a couple of other patterns. The field/vertical sync is non-standard and there is no interlace. The subcarrier to H and V realtionship is wrong too. None of this matters much if you're setting up an older TV set. I've not tried it with any modern sets or other kit with digitally based video decoders. I wouldn't expect it to work very well.

It may be worse than this. The output may not be 625 lines (or 624 if not interlaced) at all. It may be somethng completely non-standard. But this is less likely.

For viewing purposes find an old portable TV with video input. Likely to be colour as few if any B&W sets had AV inputs. An NTSC set should lock to the roughly 625 line signal. The vertical hold and height might need adjusting. Alternatively an old CRT based video monitor. The sort that might have been used in a TV studio or CCTV system.

As others have said, you'll need to look at the video waveform with an oscilloscope to find out much more. Even then, unless you're familiar with TV waveforms, it can be tricky to find all the quirks. As for using a digital capture device, the answer is probably no. You can try different devices and you may strike lucky but more likely you'll get nowhere fast.