The Viking is a bit different to service.
Instead of removing front covers to reach the main parts of the machine,
you service it from the rear.
Here you can see the rear cover removed.
On the left bottom is the drive motor.
The belt on the left control the rotation of
the upper and lower shafts.
Across the bottom left to right are the shafts
to control the hook and feed assemblies.
At the top center you see the cam stack.
The motor is an electronically modulated AC Motor.
The Drive Belt is an item that required
checking when doing a service.
If it is too tight or loose, the belt will not function properly.
Using the finger flex test, press against the belt.
If it flexes an eight inch or so, it is good.
If it fails to flex or appears to have slop, adjust it.
To adjust the tension on the belt adjust the tensioner
Cam stacks must turn freely and their trackers
must align with their appropriate grooves.
These may require adjustment due to
sticky old lubricants, misalignment, or debris
To learn more about sewing machine repair,
check out http://www.FixSewingMachines.com.