Quoted from Grizlyrig:Maybe the capacitors are dried up and not keeping up...
Would love to see a video of this happening and let others more experienced see it to give a better diagnosis.
-Mike
I agree it's something with the capacitors - or heat related to connectors. Try reseating all the connectors and seeing if it the behavior changes (that way you know it's time to replace them, as well.... start with any that go directly to the transformer.)