RCA tube set with no picture and a strained flyback

[irext]

The other thing to watch out for, all though not relevant in this case but worth mentioning, is when attempting to use a CRO on a live chassis set. The set under test must be connected to the mains via an isolating transformer otherwise bright blue flashes occur! ie path to earth via the CRO probe and CRO. Usually results in damage to the probe, the CRO input and the set under test. It's particularly spectacular in Aus as we have 240V mains.