Just swapped out the 6x5 rectifiers in the M3 and it switched on but after about a minute the power went off. One of the mains fuses in the back of the pre had blown so chucked the old 6x5s in with a new fuse and it powers on but I’ve got no heater on the left hand 6x5 and a constant buzz out of the left channel. Swapped the 6x5s over and the left one still has no heater but the right does so they are ok. Both the 5687s have got the heaters on ok.
Any ideas? praying the output transformer hasn’t gone