That's great, hope it keeps running good . You're very welcome, happy to help.
In a case like that, that is why I asked for wiring diagram.
Get you an inline ATC Automotive fuse holder and a lot of 3 amp fuses.
When this happens, splice it in at transformer power wire on 24vac side.
Then, looking at wiring diagram, reconnect one section of circuit at a time.
Keep following the diagram and adding a section at a time until fuse blows.
Then, if that wire is ok, the component it connected to is bad.
Take care and best wishes,
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?