9VT1 and ballast

[jeyurkon]

Originally Posted by compucat

I would agree with that, they are durable sets. I have a Motorola 9VT1 8" electrostatic set from 1949. It is my back and white roundie and it is well made and not difficult to work on. I need to make a ballast tube replacement for it as I was watching it and it just turned off. I knew right away what was wrong. I need to get it out of the attic and repair it. I used to have it set up and in regular use when it was working. Although Motorola sets are designed to be relatively inexpensive, they are well made and perform nicely. I would not hesitate to work on another one. Even though it was considered a "cheap" TV, many are still around and serviceable 60 years later. You cant say that about today's cheap Walmart sets.

I have a 9T1 that I recently purchased to restore. I've glad to hear that they perform well. One section of the ballast is burned out so I decided to rebuild it the hard way.

After a bit of research I'm guessing the alloy of the wire is 70% Ni and 30% Fe. It has the right temperature coefficient and seems to match the resistance of the wire in the ballast. So, I ordered some 37 qauge MWS-120. Buying it from MWS was a mistake in terms of cost. The Next time I will order it from resistancewire.com

I don't think it'll be too difficult. From reading past posts I noticed that your ballast burned out in 2007 or earlier. If my rebuilding is successful, and you're not in a hurry, I'd be happy to try to rebuild yours. If it's not a JFD brand ballast I might need to know more about it before agreeing to try it.

Why rebuild a ballast this way? Probably for the same reason I want to restore a set. That I can't explain either.

I'll be awhile before I can get the set running as you can see from the attached photo. It didn't exactly arrive in good condition.

I tried to test the 8BP4 using my B&K 465. I made an adapter for it. The tube doesn't show any shorts, but the emission is near zero. I'm not sure whether to believe the reading or not. It might need much higher bias than the 465 can supply. I realize that the tester won't find other problems like bent deflection plates. Has anyone had sucess trying to measure the emission of this CRT?

John Y.