I have a beautiful p.s. with the Model 15. The 3/10 amp fusetron is open. It appears to be in the secondary feeding the bridge rectifier. I replaced the selenium stack with a nice solid state bridge...no change in voltage output. What's with the fusetron? Do I have to use one or can I replace it with a standard 3AG 3/10 amp? Larry www.antiquetelephone.com