Just to clarify:
The DT50 fuse rating for the power fuse is 10A. SLO-blow type
Secondly, I did have it repaired at a Line6 authorized service dealer and they mentioned nothing about the cause of the transformer failure, which I believe they should've checked for before just installing a $180 part and giving it back to the customer. That led me to believe it was just a case of a transformer dying out, which I see at my job all the time with 5KV airfield lighting. From what I have read on this forum in several threads, was that this was a common failure that had a service bulletin written up on it, and had several defective transformers replaced under it. That may not be the case, but I just posted what I have read on the subject
As I said, it's fixed, and I didn't expect Line 6 to cover the expense either way. The very least they could've done was give me an explanation of the bulletin I questioned, and given me specific reasons why mine did not fall under it (btw they never mentioned the bulletin to be about the fuse only). A possible reason of failure, as was given above, would also have satisfied my inquiry about what may have caused this problem so I could do some preventive checks and maintenance to ensure I don't have the same problem in the future. Had they told me a bad tube could cause this (which I asked about when I dropped it off) they would've gotten the extra money for replacing all of them for me while they had it in their shop being these tubes are hard to get if you're not a service dealer...