Hi all,
First post here, so I'll try to keep it short. Thanks so much for this incredible resource! Will preface the below by saying I'm relatively handy and repaired mobile electronics professionally for a couple of years, but am very new to high-voltage / mains current stuff, so very cautious approaching this project.
I recently curb-shopped a bootleg Puck-Man (that's what it says on the PCB) cocktail cabinet. Many of the components, including the WG K4713 monitor, appear to be from a Defender machine. The game board has some bad RAM (I think), so I've set it aside and decided to do a Raspberry Pi MAME setup for now. If at all possible, I want to keep using the monitor.
I've done a load of reading on this forum and others, and managed to do some preliminary use-case tests. I recreated the wiring that was in the cabinet on my work table, built a GERT VGA 666 adapter kit for the the Rpi (it's a model 3 B+), spent hours messing with the hdmi_timings, and got a picture that more or less fills the screen. Whites are nice and bright, the picture seems fairly stable, etc. I had to flip the image in software because the monitor's yoke cables are inverted (possibly because it was vertically oriented in the cabinet?) and I don't want to go prodding the internals just yet.
The biggest problem so far is, from what I can tell, I'm getting red, green, and blue in the 64-odd gradations the GERT 666 offers, but anywhere there should be grey or brown some other dark/neutral tone, I only see black. For instance, here's my Gauntlet II title screen:
And here's how it SHOULD look:
The high score screen also suggests I'm getting at least some amount of each primary color.
I tried the obvious fixes: hooking up my adapter to VGA LCD monitor to ensure I didn't do a bad job building the kit. I even bought another pre-built GERT board just to be sure. Both give the same result (normal color spectrum on the LCD, no greys on the WG). Today I breadboarded a VGA signal amplifier per these instructions:
http://members.optusnet.com.au/eviltim/vga2arc/vga2arc.htm. It helped stabilize the image a bit, but had no effect on the color issue.
My completely unprofessional sense from reading the FAQ is that a cap kit may be my next recourse, but I haven't been able to find any threads addressing my specific issue (no greys vs. missing R, G, or B), so I thought I'd post here before tackling the whole CRT discharge/disassembly bit. Other things I haven't tried are adjusting the black pot -- the manual for my model says it's "factory pre-adjusted" and shouldn't need tweaking, and all the warnings around here about ruining convergence by tweaking pots on the board have stayed my grubby little fingers.
Anyhow, deeply grateful for any advice/redirection/cautionary critique y'all can offer.
Thanks much,
bryan