Arcade Monitor Keep Alive

Arcade Monitor Keep Alive Project

Rayslogic Home Propeller II DonkeyKong 2 Mame P2 To Arcade Monitor Project

The purpose of this page is to preserve info on how to keep 80's original arcade monitors alive.
Had an awakening when my Sanyo 20EZ monitor picture quality became very poor
I've learned some things while getting it fixed:
- The electrolytic caps all go bad after ~20 years. So, you need to replace them all with a "Cap Kit"
- Luckily, there's someone in my area who does this: TheArcadeBuffett.com - Repair and service for arcade game monitors.
  - He also found that the sync pulse generating IC chip was bad on my board
  - He also did service on the electron guns to bring them back like new
  - He also adjusted the pots on the yoke
  - Because I was in the area, could bring the whole monitor assembly and didn't have to remove the circuit board
- DO NOT PLUG MONITOR INTO WALL OUTLET - It's designed for 100 VAC, not 120 VAC, hence the power transformer inside the chassis
- The main IC chip on the circuit board (LA1464, see below) is very rare and can only be gotten from old boards. Current cost is ~$40 for replacement, could go up in future.
- To adjust screen, adjust right pot on flyback transformer (adjust High Voltage and therefore screen brightness) as well as the display pots on bottom left side of monitor. Buffett has youtube videos on how to do this.
- My chasis was retrofit with a JAMMA interface and so has an extra video inverter board. The original Nintendo boards had inverse video (black was white) signals, but the new stuff had non-inverted video, hense the inverter board.
- The video signals connect to the bottom-front-right side of the monitor's circuit board.
- Buffett recognized the slight, faint, burn in on my monitor and it was a pool game. This isn't so bad really because it's really only at the edges of the screen.
Here are some docs on the Sanyo 20EZ from the web:
The LA1464 chip, sync seperator, is the brains of the monitor and mine was bad.
- For my monitor, that meant the horizontal retrace lines were visible when they shouldn't be
- Horizontal retrace lines are white horizontal lines (vertical in my rotated monitor cabinet) about 1" apart
- The retrace lines can sometimes be fixed by simply turning down the screen voltage with the flyback, but that wasn't enough in my case
- The ArcadeBuffett tried changing a few transistors, but that didn't help. Then, he replaced the LA1464 chip and it was all better.
- The LA1464 chip seems to be in short supply. Seems they are all used and cost $30 to $40 each. There are no substitutes it seems, so may be an issue when these are all gone...
- Found a japanese datasheet for the LA1464
Here are some scope traces of the combined sync signal when using my computer and Mame (forgot which game, maybe galaga or frogger):
Here are scope traces of the combined sync (and one of a color) when using the Twin Cobra PCB that came with the cabinet:
There is one minor issue with my monitor to sort out still... There is something strange going on with horizontal lines of video where the left side of anything is highlighted and the right side shadowed. Think it might be the video inverter board as display looked perfect when Buffett was done with it.
- Going to try generating test video display using a P2 microcontroller and connect before and then after inverter to see what's going on.