RGB to VGA Converter Issue Please Help

[BootyHarvest]

I've successfully modified a NTSC "Nintendo 64" video game console to output 15KHz RGB video.
The console doesn't output a sync signal itself, but a SCART to 4 RCA (RGBS) adaptor that I'm using does.
My 15KHz RGBS source displays on studio broadcast monitors (15KHz YUV/RGB) with RGBS inputs.
But with a Ambery AV-1 EE0240 "Component/CGA to WXGA Converter" (RGB/YPbPr to VGA scaler), I don't get a picture on VGA-compatible monitors.

The scaler works fine with analog YUV component sources like Betacam (Y, R-Y, B-Y) and DVD (YPbPr).
Why won't it work with my 15KHz RGB source that works fine without the converter?

Note: The VGA-compatible monitors I've used support the resolution and scan frequencies.
And I think I've been using the right cables:
* 5 RCA to HD15 (RGBHV [using the "H" for the composite sync line] to VGA)
and as a backup
* SCART to HD15 (RGB to VGA)

To add to the confusion, either the description and manual are incorrect or the converter doesn't scan double common 15Khz RGB sources.
Explanation:
1. Fact: CGA is digital RGB. And I think it's interlaced.
The manual calls CGA "non-interlace" and "analog" (PDF doc). Either the manual means analog RGB and is using the term CGA loosely or the converter upscales RGB only in digital form (CGA).
2. Fact: YCbCr is digital YUV component (the digital equivalent of YPbPr).
The converter does upscale analog YUV component sources. The manual either means this or the converter can upscale digital YUV component sources too.

[cgm]

I've successfully modified a NTSC "Nintendo 64" video game console to output 15KHz RGB video.
The console doesn't output a sync signal itself, but a SCART to 4 RCA (RGBS) adaptor that I'm using does.
My 15KHz RGBS source displays on studio broadcast monitors (15KHz YUV/RGB) with RGBS inputs.
But with a Ambery AV-1 EE0240 "Component/CGA to WXGA Converter" (RGB/YPbPr to VGA scaler), I don't get a picture on VGA-compatible monitors.

Are you using composite video for your sync source or are you using a LM1881 to create a "clean" composite sync signal? A lot of the studio monitors will take composite video as a sync source no problem, it may not be the case with the Ambery adapter. Information on the LM1881 can be found here: http://www.gamesx.com/misctech/lm1881.htm

[BootyHarvest]

To cgm,
First off, thanks for responding.
I don't use composite video for sync because (if I remember right), it didn't work when I tried it. I do own a LM1881N chip (composite video in, composite sync out) but it didn't work when I used it (but then again, I could've wired it wrong).
For these reasons, I bought a SCART to 4 RCA adaptor that generates composite sync. As I stated before, using this, I get a stable picture. But when I sent it to the Ambery converter (which accepts RGB with all forms of sync), it was all garbled.

I've been told 2 helpful things though that may explain why I'm not getting a picture:
1. The device accepts CGA RGB, and consoles (even RGB mod'ed ones) can't output CGA RGB.
Note: I just assumed Ambery was mistaken when referring to CGA. And I thought that as long a RGB signal was 15KHz and analog, the device would accept it.
2. The RGB on the N64 is probably weak. So an amplifier to boost the signal, thus the sync, might be a fix.