$3000 swtiches it back off.
The Lambda display file is fixed, starting at position $407D (the first byte is a NEWLINE as on the zx81, thus $76).
The attributes file is accessed writing at position $207D, and obviously it can't be read because it overlaps the ROM locations. Characters corresponding to the NEWLINE positions alter the border color.. so probably it is easy to generate striped borders !
First of all it appears the interface does work in general when used with a 16K RAM expansion (DIY, SRAM based, WRX enabled) in that I can initialize the color mode (random attributes shown), overwrite them all as recommended in the example program and set individual attributes to my liking. On my ZX81 (Rev. 3, simple transistor based composite mod [not the 'complex' 555 based one which adds a backporch] - probably not required due to a 2C210E ULA, no inverse video - quality on my Sony PVM 9044QM is great) the output quality of the color addon is extremely bad, some lines are distorted, the colors don't exactly match up. Any ideas what could be done to improve the picture or is this something I have to live with?
Picture here: http://i.imgur.com/R4GTBwp.jpg
Back to the ZX81 it is for me it seems ... while the picture is fine on the Sony PVM it gives me a solid white screen on the Bravia LCD.
Building the back porch/level addon (once again) by zxzigg as of now.
EDIT: Backporch generator enables the bravia to display a proper picture but otherwise makes things only worse.
No idea what exactly fixed it ... I added a 1K variable resistor in the footprint set for one (previously hardwired with a fixed resistor) and replaced the orange trimable capacitor (which broke) with a yellow one (too lazy to look up the values right now), also added decoupling caps for every IC.
Color levels still seem to be a little off (have to tune the brightness up to 3/4 instead of the default 1/2) but that's ok for now - I'll stick with tuning the video monitor for now.
I try to understand the schematic of the Lambda Color Module.
I've tried to match ICs on the picture and the schematic.
There is one IC and drawings on the schematic I don't understand. Can anyone enlighten me?
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube