RGB to composite converter - issue

[ultrasyd]

Hello !
  I started a new thread even if I already asked about this in an other topic, but   first i choosed to give a try with Bryce's RGB to composite converter -   so the S-video adaptater was not the good topic. It was easier to get the components   for this one as i could find the MC1377 in a local store, and i thought   the picture posted with the schematics would help (and it did a lot -   but not enough : )
  Still ... I failed !
 
  Well, i had 2 PCB made, got all the components. Started soldering ...   quite easy and even pretty enjoyable after all. I even find it doesn't look too bad and each component seems   to be at the right place, in the right sense (only important for the   ceramic condensators, MC1377 & LED ?)
  For the DIN 6 cable, i was very stupid ! I saw a blue, a red, a green   (even 2 kinds of green !), a yellow and a black wire, so i thought i just had to   solder them where needed. Of course, the colors in my cable have nothing   to do with the actual colors ! I saw pictures of the pin-out on   CPC-wiki and other websites and corrected the wires, but i'm never sure   with this kind of plugs : is the drawing viewed from front or back ? I'm   pretty sure i did it correctly now but there is an issue :

  With the DIN-6 video cable unpluged : The LED of the converter is ON, the CPC is on, the floppy drive works, i can run a program and get sound.
  With the DIN-6video cable pluged : the LED turns OFF, like if the converter doesn't work anymore - and the cpc works.
  When i unsolder the ground wire on the PCB,   the LED stays ON and the keyboard still works. Like if this ground wire causes an issue. But in any case, i've got   nothing outputed through the cinch (i tried with an audio cinch cable,   but that doesn't make a big difference ?), so i don't know for the other wires.
 
  I let you see what i did with the video cable and the wires soldered on the PCB :
  http://ultrasyd.free.fr/demo/conv01.jpg
  http://ultrasyd.free.fr/demo/conv02.jpg
 
  There is two 0-12v places on the PCB - I took the pink one (shown in the 1st picture) to plug   the cable from the keyboard. The other, just upside the wires of the   video cable, goes to my PSU. Is this important or possible to invert ? Should i invert ?

Any idea about what is wrong with this video cable ?

Thank you in advance for the help ; )

[Bryce]

Hi Ultrasyd,
         the PCB looks good and all the parts seem to be soldered in the right place and the right way around, so I assume the PCB actually works, especially as the LED is ON. The only thing that's concerning is the fact that you have a red wire connected to pin 6 (the centre pin) This is the Luminance signal which isn't required for the PCB to work. Where is it connected to??? Connecting this to 12V or Gnd could damage your CPC.

Bryce.

Edit: Are you sure that the 12V output that goes on to your CPC isn't the wrong way around? The positive should be on the outer ring and the GND in the centre. The opposite of the 5V socket. This would cause the problem you describe.