[cork]

Hi Andy,

The main problem they seem to have with old , aired-up CRTs is bits of junk in the tube, such as little pieces of glass, and after a while, the dag inside the tube deteriorates in the presence of air, and starts to fall off. Baking them is a standard part of rebuilding. They bake them to try to get the air to come loose from everything while they are pumping. After they do the pump down and blow the getter(s), they activate the cathode in much the same way that we "rejuvinate" them, lots of heater overvoltage, and pulses of high cathode current to remove surface inactive stuff from the cathode. There used to be a place here in town that was pretty good at this rebuilding stuff, including tri-color tubes. But they were done-in by the crush of cheap stuff from Asia. The trouble is the cheap Asian stuff seems to keep on working almost indefinitely, until people just throw away sets with perfectly good bright CRTs.