1A/250, output fuse I think. But, it appeared in tact and I believe it may still be good. I replaced the fuse (finally arrived) and it would not power up. I'm quite sure now the transformer is the culprit. For me taking it to a service center isn't feasible. My nearest one was in Lynn Haven, outside of Panama city. I'm pretty sure they aren't there but will be rebuilding courtesy of Hurricane Michael. A bud has family there and they are rebuilding, he says not much was standing afterwards. My second service center is in ATL and a 4 - 5 hour drive. I haven't opened it up as of yet to check the other fuse because I'm willing to bet I'll have to order it as well. The down side of living peacefully in a rural area! Its really a shame, I bought this amp the later of 2016. I bought a house and spent the next 18 months getting it like I want it before I took time the time to play any at all with the exception of an hour or 2 here and there. I bet this head doesn't have 50 hrs max on it. I may end up going this route ( https://mytubeaudio.com/tag/new-transformer-line-6/ ) because all the research I have done has led me to believe that the OEM is a faulty design with low quality control. Biasing with dual probes will be out of the question and I will have to find someone with an oscilloscope after replacement. Its a great head, a true tone monster! Its me second one as I was forced to sale off all my gear several years back. I can't justify OEM after reading all the other horror stories!