Weston Analyzer Model 980


I'm working on this old Weston Analyzer Model 980 VOM.


I haven't found a manual for the plain Model 980, but I did find a manual for the Model 980 Mark II. Anyone know of a source for a manual for the original 980?


The range and function switch uses tracks on the PC board. When I received it, the ball-bearing for the click-stops was rattling around inside the case. It's supposed to sit in the little hole in the brass leaf-spring to the right of the switch shaft.


Unlike the Model 980 Mark II, the plain 980 doesn't appear to have any meter protection diodes.


The 980 Mark II schematic says the meter should be 50 µA and 1125 Ω.


Mine measures 98 Ω, and I put up to 3 mA through it without budging the needle. The movement works freely for the most part. It does stick a little at about 3/4 scale. This must be from corrosion on the bearings, as there isn't any crud in the gap.


I pulled the meter movement out of the case to inspect it.


The rear pivot looks OK. I can see the connection to the winding on the bobbin. I can't see any damage to the winding. The insulation on the pivot looks good, too.


The front pivot also looks good.


As on the rear pivot, I can see the connection between the front pivot and the winding, and the winding looks fine.

Any ideas on the source of the partial short circuit? I can't spot anything, so I'm left supposing that someone overloaded the meter and cooked the insulation on the winding somewhere where I can't see the damage.

I suppose I could take the movement apart and try to rewind it, but that seems like a bear of a job.

© Steve Byan 2011-2019