thorlabs thermoelectric controller

[Corryl]

I’ve got a Thor labs thermoelectric controller that I took a risk on hoping it was just a fuse…but of course it wasn’t.  I made an offer and it was accepted so I got it fairly cheap so if it’s totally fried, it’s not the end of the world and I bought a lot of expensive analog parts to use in other projects.  But, if I can make it work and use it for some “cool laser stuff” all the better!  So, I figured I’d dig in regardless! 

The only obvious damage is a charred resistor that’s either 10 ohms or charred beyond legibility.  It measures 40 ohms currently.  It was a limiting resistor to a zener marked zpd 3 with its breakdown voltage measuring  2.3V currently.  Is it safe to assume this was a 3V zener, or is there something kooky like the marking only gives part of the voltage and you should just know what the part after the decimal is or measure with a multimeter!  (Hopefully not but I’ve seen crazy stuff before.

The only reason I question the zener voltage is it is connected across a pnp bjt and may be the “regulator” for the digital components.  (Which would explain the lack of powering on).  It just seems like an odd voltage to use…2.3V after the bjt drop.  I’d have to reverse engineer some more to really know, which I’ll do, but it would be a nice story to say someone plugged it into 240, and the most expensive component in the system didn’t act as a fuse, instead a resistor and zener did!  Yeah, that’s probably far too optimistic…