Thanks to the source code for the MAME DTC01 DECtalk driver, which is apparently the only place there is any information on the self-test error LED codes, I determined that there was a failed HM6264LP-12 static RAM chip. The error code narrows it down to a pair, and swapping narrowed it down to a single chip. After replacement with an HM6264ALP-12, and powering up, I was delighted to hear "DECtalk version one point eight is running." At some point if I get sixteen 27128 or 27C128 EPROMs, or maybe eight 27256 or 27C256 with four jumper changes on the board, and two 82S191 or equivalent PROMs, I might upgrade it to 2.0. I've only ever seen firmware versions 1.8 and 2.0, but there are rumors of an intermediate version and a version 2.1. Does anyone have these?