"I believe any electrician who can read electrical schematics should be able to read and understand straight forward ladder logic. After all, what is the difference between the two?"
I think it has something to do with all the flashing lights on the plc, it mesmerizes electricians and maintenance men.
In all honesty a large majority of electricians have no need to read ladder/machine schematics because they never deal with control work of any kind. Their primary duties are to run conduit, wires ...ie distribution. I would state that an industrial maintenance electrician
"should" be familiar with ladder/machine schematics and learn (and/or trained) how plc's interact even if not how to actually use the program to troubleshoot. In all reality though this is not always the case, employers want people to know these things when they hire them and training seems to be (in many cases) not something companies deem necessary. The employee is expected to know/learn on their own.
As for troubleshooting I agree with PLucas on the use of the schematic if available. With a schematic a knowledgeable/trained person may be able to determine the problem without the need to look at the program. I also believe a documented copy of the program/code can make it easier to troubleshoot. I always make copies of programs and reverse engineer/document them when I dont have or cant get the code from the manufacturer etc.
I am going to tell a story now, I took a temp position at a Dairy processing plant that was looking for plc/control techs, I was placed at top level (F1) for their maintenance people but I had to work nights. The night shift supervisor was a retired Marine that took a 2 year tech school course while working as a PM mechanic (F3), after passing the maintenance course he was made F2, two weeks later he was the supervisor. NO prior experience in this field at all. NOW comes the machine troubleshooting story. The dairy had a line that brought milk cases thru a washer and then fed them to be loaded with product..ie milk. This particular line was running half gallon containers, the containers would be positioned then dropped into the case then sent to freezer/cooler. 3 shifts worked on this case packer, changed every pneumatic valve etc on it. I was new but the night tech called me over and I checked the inputs/outputs and determined one output led was coming on BUT there was no power coming from the output. I dont remember the specific model (it was an AB) but it was one you could exchange the EEPROM in and retain the program. They had a spare. The supervisor decided I was wrong and AGAIN changed every part on the machine, they worked on it till 5 AM changing parts. Then they asked me "Can you exchange the plc?" I said yes and pulled the old out, moved the prom over and installed the new. It was up and running in less than 30 minutes from the time they said ok you can do it.
My reason for telling this story? People do not always possess the knowledge you think they should have. Companies dont always hire or train people properly for the positions they fill.
I refuse to work under anyone dumber than I so I didnt work under that supervisor another night.
As for helping a company troubleshoot it takes a few key factors:
1. People or at least one person willing to learn. On his/her own if necessary.
2. Companies willing to provide some form of training.
3. Management/Supervision that is knowledgeable.
Its rare to find one of the above let alone all 3.
As an after thought, many maintenance/electricians etc spend years being good at what they do, then are expected to KNOW anything NEW that comes along and how to deal with it. I know many people and I will say especially engineers do not understand WHY a maintenance man doesnt understand something or learn about it. You took your route to learn what you did because of desire and intelligence, not all people have the desire or the intelligence of others. People are different, that said that maintenance mechanic, electrician etc may be GOOD at his/her job but just doesnt have the knowledge YOU think they should have.