There are a few essential tools that are worth mentioning as a part of this series.
Here's the first one:
Modular Circuit Technology Mod-HIC IC Tester
Tests many of the chips used in synths--CMOS, TTL, and some memory chips.
An indespensible tool that can even identify certain chips if the writing's been removed.
These are no longer made and occasionally pop up on eBay.
You know, I honestly thought every tech had one of these until it was pointed out to me that they're rare!