>>> Dave, thanks for your help troubleshooting this issue.
No problem. I just had to keep your nose to the grindstone
!
A bad connection should appear as a resistance. So checking the resistance from one point to another should give you a clue. However, once a current is drawn, there should be a voltage that builds up across the bad connection. You then use a differential voltage measurement technique to find where the fault is. Not only are PCB solder connections a problem - but also cables. Most of my simple 'fixes' are bad connections - either in the solder joints of the power connectors or in interconnecting cables.
Get a few repairs under your belt and you will start to build up some useful experience. However (a word of warning) once you have repaired a few machines, you may start to get complacent and concentrate on things that you now know fail. This can lead you astray. You really should be like a detective and follow the clues based upon a test methodology.
Also, document each step in a notebook. You will need this later when you get lost and need to backtrack. Also, once you have found the fault(s) you can re-read your notebook to see how you got there - or more likely, where you got distracted in your testing.
On a small number of occasions I have found in my notebook something that couldn't be accounted for by the fault I had found. Unknown to me, the first fault I was chasing when I started out mysteriously fixed itself and was replaced by another fault! I had found (and fixed) the second one... I hunted a bit more and was happy to find (and fix) the original fault in the end. It would have only come back to haunt me in the long run!
Dave