Hi, Thought I had a good result with getting a new U1281A off eBay (Singapore) for a little over $400AUD, and when it arrived all brand new in the box all seemed well.
Reading the manual like all good boys do, and playing around with the setup, I noticed every now and then it would show OL on the DC range, even with no leads connected.
I had a play and it seemed to be normal most of the time, then I was trying out the resistance range and it started showing random resistance figures in the KiloOhm range for a known good lead across the inputs. I opened it up and had a look under the microscope and here's what I found..
A probe with my trusty old Fluke 85 shows this is open circuit between the pin and the via next to it, and the data sheet says this is the inhibit pin of the 4053 multiplexer.
As I don't have a circuit diagram, I can't be certain if this is the fault I am seeing so I dont want to void my warranty (if I haven't already) by "fixing" this joint. It is very tempting though.....