This repair started as a consequence of another test gear being checked (a Tektronix DC-510 counter, which will be soon on the Workbench pages). I fired up my second 8640B (which had been troublefree since I got it some years ago)... and it was not working fine!. It showed wrong frequency readings at all ranges. Immediately I knew what had happened: the dreaded rotary contacts were falling from their supports!
So I opened the unit and got out the RANGE and FM DEVIATION ASSEMBLY (as I did with my first HP-8640B some years back). Once dismantled, yes, one of the contacts was almost loose:
This is a general view of the switch assembly parts:
And then some close views of the parts:
OK so, what to do now?. In order to get the contacts back to its place and stay there some time, I used a bi-component epoxy glue. Here you have detailed views of the contacts back in place with epoxy:
Next day, I put back the 'kit' in its original assembled form:
And got it back to its place in the HP8640B. Once the unit was checked, I got it back to the shelf:
Success!!!
