VGA to NTSC conversion?

[N2IXK]

Does anyone have a recommendation for converting VGA signals from a PC into NTSC composite video? I am looking to incorporate a laptop into my shop AV system, and purchased one of these guys from eBay:

http://www.ebay.com/itm/400858906982

It basically works, playing back .avi, .mp4 and other formats through VLC media player. But the output signal is NOT really NTSC compatible, with the negative going sync pulses being far too large, and the luma/chroma content compressed into a much smaller portion of the overall signal. As would be expected, contrast is poor and colors are washed out. I have attached 3 shots taken from my waveform monitor showing what is going on. First shot is the output from my bar generator, showing that the WFM itself is properly calibrated. Video signal looks great, covering the range from -40 IRE (sync tips) to +100 IRE (peak white), with pedestal at 7.5 IRE.

The second shot shows the output from the VGA converter. Pedestal level is OK, but the sync tips are WAY offscale, with maximum positive signal level at around 30 IRE. Third shot shows the complete signal onscreen, shifted upward with the vertical position control.

I opened the unit up to see if there were internal adjustments to tweak, but nothing found besides the NTSC/PAL selection DIP switches. The heart of the thing is a big chip labeled "XY1945" (No manufacturer logo), with some flash memory and a serial EEPROM and not much else inside. A Google search for the chip datasheet turns up nothing. I was hoping to get some basic application data to see if this thing is just poorly designed, or this is an inherent flaw in the chip itself.

Has anyone out there found a VGA to NTSC converter that actually puts out a standards compliant composite signal?