Both of mine were non working, too. This one just needed batteries. The other was sold as working, but wasn't, and after complaining, I got a full refund, and fixed the U32. Its display is dying, but I've got LEDs to repair it (I've read your post on that repair).
As to what lead me there, I figured if it's not capacitors, it's usually an active component. I marked all the semiconductor components driven by +6 and figured it would be getting hot. I felt them all. None were warm, then I remembered that the components on hybrid U32 are not shown on the schematic, and checked them. As usual, in hindsight, I should have been smarter earlier.
Now to put it back together, replace the LM358 and regulator and do some calibration.
Thanks for the help. It's easier when you can bounce ideas off someone else.