GT:
"looks OK" is not an indication that all is working properly..... a lot of
faulty components look OK with no signs of over heating or other obvious
defects. These things need to be tested with test equipment, a working
DMM or VOM test meter is required if you are going to effectively
troubleshoot this problem. First priority would be to repair your test
meter, borrow one, or purchase a new one.
Now I am thinking that if you are in need of this kind of advice that you
probably won't be able to fix your Weller w100 no matter how many working
meters you have. I could be wrong, please forgive me if I am.... and good
luck getting your soldering iron working.