Improved Video Board for Yamaha MSXs version 1.1 Copyright (c) 2016 RBSC WARNING! -------- The pinout of the RGB connector on the new video board differs from the original pinout! On the new board pin 3 is connected to +12v supply. When making RGB to SCART cables or when using such cables designed for the Japanese MSX mashines, please make sure that you connect the +12v to the correct SCART pin - pin 8. Connecting +12v to this pin will switch the TV/monitor to 4:3 mode. DO NOT connect the cable from Yamaha YIS805 to this video board! The pin order is different on the YIS805 and you will damage the board if you connect it to YIS805! It is advised to power down the computer before switching between PAL and NTSC in order to avoid damage to the encoder chip. Settings -------- There are three 3-pin jumpers on the video board. These jumpers are used to set the color encoding for the S-Video and composite video outputs. All jumpers must be set identically. When the pins 1-2 of the jumpers are shorted, the NTSC encoding is enabled. Otherwise, when pins 2-3 of the jumpers are shorted, the PAL encoding is enabled. Please note that the jumper settings do not affect the RGB output. When setting up the board, it's recommended to measure the voltages on the outputs of 4 potentiometers (variable resistors). The correct voltage setting is required to form the picture on the composite video and S-Video outputs. The recommended voltage for the CSYNC variable resistor is 1.3v, the recommended voltages for Red, Green and Blue variable resistors is from 1.5v to 2.0v depending on the desired saturation. The voltages on R, G and B must be the same to avoid color distortion. Each color should be tuned after setting it as background - for example when setting the blue color's voltage, use the "color15,4,4" command in Basic to set blue as background color. Notes ----- Please use the following oscillators: 3.579 MHz for NTSC and 4.433 MHz for PAL. Using other oscillators may cause undesired side effects. It is recommended to use the 74HCT04 chip for the frequency generator circuit. The HC series chips may also work, but the HCT series is highly recommended. There may be artefacts on the color transitions in the composite video's output. These artefacts can be removed by carefully adjusting the corresponding trim capacitors (C14 or C20). The sharpness of the composite video output can be adjusted by the C23 trim capacitor that is marked as "YTRAP". If you are using a jumper pin row instead of the original cable connector, be careful to connect the cable from the MSX's main board correctly. Incorrect cable connection can damage the video board and MSX! IMPORTANT! ---------- The RBSC provides all the files and information for free, without any liability (see the disclaimer.txt file). The provided information, software or hardware must not be used for commercial purposes unless permitted by the RBSC. Producing a small amount of bare boards for personal projects and selling the rest of the batch is allowed without the permission of RBSC. When the sources of the tools are used to create alternative projects, please always mention the original source and the copyright! Contact information ------------------- The members of RBSC group Wierzbowsky, Ptero and DJS3000 can be contacted via the MSX.ORG or ZX-PK.RU forums. Just send a personal message and state your business. The RBSC repository can be found here: https://github.com/rbsc -= ! MSX FOREVER ! =-