From bf10dd16fac7bf04aafca75661d92abfc1702d1f Mon Sep 17 00:00:00 2001 From: Scott Stone Date: Thu, 20 Feb 2014 20:15:26 +0000 Subject: [PATCH] (MESS) a7800.c - Added more details and clarification regarding the potentiometer. [Robert Tuccitto] --- src/mess/drivers/a7800.c | 52 ++++++++++++++++++++++++++++++++++------ 1 file changed, 45 insertions(+), 7 deletions(-) diff --git a/src/mess/drivers/a7800.c b/src/mess/drivers/a7800.c index 466f1acefe4..fb0e10244d4 100644 --- a/src/mess/drivers/a7800.c +++ b/src/mess/drivers/a7800.c @@ -74,8 +74,12 @@ 2014/01/02 Robert Tuccitto Corrected joystick buttons assignment & minor palette notes cleanup. - 2014/01/09 Robert Tuccitto Positional description for difficulty - switches added. + + 2014/01/09 Robert Tuccitto Positional description for difficulty + switches added. + + 2014/02/15 Robert Tuccitto Added more details and clarification + regarding the potentiometer. ***************************************************************************/ #include "emu.h" @@ -171,12 +175,46 @@ depending on how poor or well it handles the signal conversion and its calibration) on a modern flat panel display, as opposed to 'gold' (~-33 degrees) on a CRT. -The system's pot adjustment manually manipulates the ratio of blue to -green/blue to red, while the system 'warming-up' causes the palette phase -shift to go higher in degrees. +The potentiometer (pot adjustment) for the 7800 modifies the delay line +regarding colors it will exhibit and is extremely sensitive. The slightest +turn can have a significant impact. -At power on, the system's phase shift appears as low as ~23 degrees and -after a considerable consistent runtime, can be as high as ~28 degrees. +A system whose potentiometer is not properly calibrated via +'CPS 7800 Diagnostic Test Cartridge' or/and just slightly off from the +desired factory settings may exhibit consequences such as too much blue in +place of green (Pot adjusted slightly too far left) or washed out reddish +tones in place of where most other systems display a darker reddish tones +(Pot adjusted slightly too far right). + +This is a result of the phase shifting of lesser degrees (Pot adjusted more +to the left) or phase shifting of greater degrees (Pot adjusted more to the +right). + +Turning the pot adjustment to the right, it can be observed that the values +of the higher end of the scale will match the lower end of the scale. +For example, after some turning to the right, the values of Dx, Ex, Fx, +can be set to match 1x, 2x, 3x. + +After further turning to the right, now the palette can be brought to make +Ax, Bx, Cx, Dx, Ex, Fx will match 1x, 2x, 3x, 4x, 5x, 6x. + +Ultimately though, too much turning to the right results in all colors being +wiped from the scale, excluding the hue begin point 1x (Which remains +unchanged while tweaking the potentiometer either left or right). + +Continuously turning the pot adjustment to the left, red and blue become the +most dominant two colors encompassing the palette with only a slight +influence of green at the highest end of the palette (Fx), once turned all +the way leftward. + +The degree range for adjustment of the phase shifting on the 7800 appears +to be as low as approximately 15 degrees when tuned all the way left, and +seems to be able to achieve as high as approximately 45 degrees when turned +right before losing all color (Excluding 1x) from the palette scale. + +For even a properly calibrated system at power on, the system's phase +shift appears as low as ~23 degrees and after a considerable consistent +runtime ('warm-up'), can be as high as ~28 degrees. In general, the low end of ~23 degrees lasts for maybe several seconds, whereas higher values such as ~25-27 degrees is the most dominant during