On Bob Roberts site, there is (or was, if the link is broken by the time you read this) a scan of a page that details how to add the missing parts to the Sanyo 20-EZ monitor chassis to allow it to perform video inversion. Since the page was scanned and not run through an OCR process, the text is not searchable. As a service to the arcade collecting/repair community, I provide this HTML based, searchable version of the document.
(Note that I am not responsible for the use or misuse of this information, and I might have copied something incorrectly! No warranties expressed or implied, and the risk of use lies with YOU! YMMV.)
20EZ Nintendo Video Inversion
|100K ohm 1/4W
|100K ohm 1/4W
|820 ohm 1/4W
|560 ohm 1/4W
The Sanyo 20EZ chassis left out components in the video circuits of Nintendo monitors for inverting the negative video to positive video, used by most game manufacturers. The early Nintendo game boards outputted this negative video, so the circuits were not needed. In later games they mounted a separate inversion board on the flyback cage to invert this negative video to a positive video for their newer games, but left a non-inverted output header for use with the older game boards. If you have the inversion board on your Sanyo monitor it can be used with the majority of the other game boards out there that have positive video. If your monitor does not have the inversion board… or it has been pilfered… you can add the missing components right on the chassis as silked. Doing this will make the single video output positive, disabling it’s use with early negative video Nintendo boards unless you add the separate inversion board, but making it compatible with the majority of game boards available today.
There have been many values assigned for the components since the early 80s, but this kit contains the part values most often referred to in industry magazines, tech mags, and in Internet articles. Even though this is a “parts” kit only, I will put the basic instructions, suich as they are, below. Although this is not a compilation of mine, I can say that I converted hundreds of the monitors over throughout the 80s for use with new game boards & found that most ops were overjoyed with the results.
Remove the wire jumpers that take the place of TR201, TR202 & TR203. Remove R12, R214 & R215. Install kit components in positions as outlined as the top of this page.