I've got a 25K7000 with a dim picture. I thought it had a bad tube, but then I measured the heater voltage and it was ~1VAC. Isn't it supposed to be around six volts?
I'm 99% certain it is (without looking at it). This is the same monitor we discussed @ BYOAC. So a rejuvenator is out until I can confirm mine is working, or I can use someone elses near me.