Aesthetix Io strange behaviour

I am no engineer, but I guess the possibilities are: 1 the new regulator was not quite the same, not correct, and broke down, 2 the tube went bad (seems unlikely), 3 something else / upstream. I wonder if this kind of failure should have made one of the fuses go, instead of components. My Io has four fuses, two inside the power supply box, 2 at the back of the box (none in the Io itself). After getting it back from repair, I changed the fuses to weaker amperage, thinking that it is better that a fuse blows. I tried changing the two at the back to 1 amp fuses, but the "B+" blew and I had to go back to 5 amp. The "Heater" fuse worked ok. I then changed the two internal fuses F1 and F2 to 1 amp (I had 5 amp in one channel - too much). It may be that this is still too much (could be 0.5A or 0.25A since we have 240 volts here in Norway). Both lights turn on, at the front, so I assume none of the fuses are gone. And it seems very unlikely that a fuse, by itself, is cause of the failure. I have also read (at this site) that Aesthetix later dropped the two internal fuses since they often blew and did not protect the components anyway.

Another remote possibility may be that the active shield power cable (Synergistic Research A/C Master Coupler X2) that I bought recently is not good for the Io, it gives some static effect, or whatever (even if it is plugged into the same course as the preamp). I know that the Io is very sensitive to the mains, and the problems have come after I changed from a Kimber power cable (standard type, no active shielding). Yet I have not seen users reporting problems with active shielding, so I consider this quite unlikely.

The mystery deepens. I brought it back to the repair shop some days ago, and got an email from the professional involved, today. He writes that they have the Io up and running once more, but he wants to keep it for further testing. He writes (my translation from Norwegian);
"I changed the fuses that had gone from 'fast' to 'slow' 0.5A. Did not find the BUSS [US] fuses that I thought I had, but found the documentation for those fuses and as far as I can see now it should be 'slow' 0.375A. For now, everything looks fine. Has been left on, for testing, yesterday and so far today. Want to test some more for checking power voltages esp around the regulator."

It could be as simple as two bad tubes in a row. Not so often, but it happens. Since this thread may be informative for other Io owners, I will keep you updated.

I got it back today, working fine. Morten said he could find no other fault, except for blown internal fuses. The were "fast", and he said, even if the amperage is larger, such fuses often blow before "slow" fuses. As far as can be seen, the new regulator and the EL34 tube work fine, and there is no problem with the Synergistic active shielding cable.
So, the mystery has been cleared up, it was one bad tube (only), the second time it was wrong fuses (my fault).