This is not a DIY post! But I may not be able to get an answer here anyway.
I work for a company that does electronic repair work. We fix computers, GPS, cellphones and so on, to the component level. I spend much of my workday soldering under a microscope. My boss has gotten access to a large quantity of Alerton HVAC modules which have been taken out of service for various reasons. I've been given the job of sorting through them and fixing them as necessary so that they can be put back on the market for sale to contractors (like you guys!).
For example, one of the modules was a TX-653P. There was a tag on this module that said "analog?". I googled up a program called "TDS" that allowed me to talk to this module over a PC serial port. I hooked up a 24vac transformer and a PC, and was able to exercise all the inputs and outputs of the module. The analog outputs did not work. I isolated the problem to an opamp, changed the opamp, and now the analog outputs work. The module went back to the people we got it from, and they tested it in a real system and verified that it works correctly.
I have other modules here; dozens of different kinds. I'm not an HVAC guy, I'm an electronics guy. I can dummy up any kind of input signal these things might want, and I can test the outputs. But I need to know how to talk to them, what inputs they expect, and what outputs they produce.
If I can get this info, I can start repairing modules and my boss will love me. But (no surprise) this information is not easy to get ahold of...
I have no interest in building my own HVAC setup, or fixing somebody else's. Neither does my company. But I realize that the kinds of questions I have might fall pretty squarely in the "DIY" category. My first question is, can anyone here help me find the low-level info I need to test and repair this hardware? If not, can you bend the rules enough to point me to a place where I _can_ get those questions answered?