transformer on 10k unit blows fuse on hp call

Hi everybody!
had a customer that keeps blowing xfmr fuse, I am new too hvac side(refrigeration tech commmercial) its gotta be outside at the hp but not sure how to test the defrost board, it was dark and a long day, emergency heat works fine, and I dont get any voltage off the compressor wire(removed themostat) postive or red wire is 28v .
I do not remember specs of hp but not important, tested yellow or compressor wire and no voltage so I know it either the defrost control board or the contact.
this is a new system I did not install but it only maybe 6 months old
ANY IDEAS???

i tried to jumper fuse to get a amp draw and it torched the xfmr in seconds

Follow the short.