Used an oscilloscope to check the R/G/B output from CGA board to the GBS 8200 ... R & B showed expected activity, nothing on the G output.
Then I noticed some haphazardly soldered inductors that appeared to be on the R/G/B signal paths:
L1 - red - C5
L2 - green - C4
L3 - blue - C3
There was activity on L2 but dodgy continuity between L2 and the green wire.
Re-soldered ... with a dab of flux ... and the colours are now perfect! Happy.
Remaining problem is the image is right-shifted.
Strapping either V_SYNC or H_SYNC invert pins moves the image to the left (but not fully), however the image becomes more unstable - even more so when loading software from tape.
So still some troubleshooting to do. I'll also hook up a BBC Model B to compare.
Success!
Ewan suggested pressing the auto-adjust on the GBS 8200 and also tying the unused V_SYNC on the CGA side to ground.
Working perfectly now!
Final configuration:
Amstrad pin 6 (LUMINANCE) was also unconnected.
The H_SYNC invert pins on the CGA adaptor board were strapped and then auto-adjust on the GBS 8200 was executed.
BIG THANKS to Ewan for taking the time over this weekend to help me get it sorted!
Then I noticed some haphazardly soldered inductors that appeared to be on the R/G/B signal paths:
L1 - red - C5
L2 - green - C4
L3 - blue - C3
There was activity on L2 but dodgy continuity between L2 and the green wire.
Re-soldered ... with a dab of flux ... and the colours are now perfect! Happy.
Remaining problem is the image is right-shifted.
Strapping either V_SYNC or H_SYNC invert pins moves the image to the left (but not fully), however the image becomes more unstable - even more so when loading software from tape.
So still some troubleshooting to do. I'll also hook up a BBC Model B to compare.
Success!
Ewan suggested pressing the auto-adjust on the GBS 8200 and also tying the unused V_SYNC on the CGA side to ground.
Working perfectly now!
Final configuration:
Code:
CGA pin 1 (GND) -------> Amstrad pin 5
CGA pin 2 (GND) -------> CGA pin 9 (V_SYNC)
CGA pin 3 (RED) -------> Amstrad pin 1
CGA pin 4 (GREEN) -----> Amstrad pin 2
CGA pin 5 (BLUE) ------> Amstrad pin 3
CGA pin 6 (INTENSITY) -> unconnected
CGA pin 7 -------------> unconnected
CGA pin 8 (H_SYNC) ----> Amstrad pin 4 (SYNC)
CGA pin 9 (V_SYNC) ----> CGA pin 2 (GND)Amstrad pin 6 (LUMINANCE) was also unconnected.
The H_SYNC invert pins on the CGA adaptor board were strapped and then auto-adjust on the GBS 8200 was executed.
BIG THANKS to Ewan for taking the time over this weekend to help me get it sorted!