I have a Line 6 Spider Valve HD100 with similar problem after 15-20 minutes will shut down
The processor board on this is facing down after the chassis was removed from the cabinet, making it a little more difficult getting at the DSP and CODEC chips
In addition to the heat sinks, I understand maybe using a fan in this area is also helpful.
Again, if all else fails, can the tube amp section still be used? Can an output from another amp be used in the amp input to carry the signal and still use the Volume at least?
Thanks in advance for any suggestions.