Hi,
i've just got an issue today using my JTM45/100 with a Marshall SE100.
This is not the first time i use it with a Marshall SE100 and i've never got an issue for the moment.
I am using the SE100 in the same configuration with my plexi with no issue for a long time.
So i was just playing the JTM with the Marshall SE100 connected with a Vovox speaker cable and plugged then into an old celestion G12T100 8 ohms.
The attenuation was at -18db.
I was playing using just one OT (the other tubes were removed) on the normal channel at max volume when i have lost suddenly the sound then i've heard a little scratch and one tube was burned.
I've decided to set back the second pair on the second OT and after 15min...same issue, another tube burned.

Any idea?

Play with all 4 tubes???

You just had one output tube in?

Or did you pull the two outer tubes?

Play only with 2 tubes. Marshall says that you can play with only one output connected, i prefer so to remove the 2 tubes for the output not used.
I have found the issue, or i think so, it comes apparently from a loosy connection on the speaker.(it's not the JTM45 cab)
I'm a dummy boy, i have lost 2 KT66.

Now i use a mixed of the 2 last KT66, they are not perfectly matched (about 4,5 ma) so i've got a more crunchy tone.