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Old 4th May 2019, 4:33 pm   #16
usradcoll1
Heptode
 
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 823
Default Re: 1940's Motorola VT 71 tv

Quote:
Originally Posted by ct92404 View Post
Dave, the schematics are driving me crazy! My tv has a TS-4H chassis. I found a "Sams Photofact" schematic for my tv, but some of the connections don't match up. On the actual tv, capacitor C1 (140 mfd) is connected to pin 1 of the "ballast tube." But on the Sams diagram, it's shown connected to a resistor. So I looked up another diagram and found a "Riders" diagram which is supposed to be for the TS-4H chassis. It does seem to show the negative side of C1 connected to the ballast. But the way the rest of the diagram is drawn is really confusing! There are like 3 different type of symbols used for ground or common connections.

I think I have the new capacitor for C1 connected now, but I'm completely lost on the others! This is so aggravating. I didn't have nearly this much trouble just trying to replace the filter capacitors on the Olympic tv!
Can you or anyone else here help me figure out where the heck the capacitors are supposed to connect? I've tried tracing the wires from the cans to the components, but with conflicting schematics I can't make sense of it and there are so many wires connected to the capacitors. It's driving me nuts!
That set is a real dandy to follow the schematic regarding where the voltages are sourced from.
The 150v source, called B+ is derived from? I spent an hour looking and comparing schematics from all the different versions and still not sure where it is sourced from. I have three of those gems on the docket for restoration.
I keep on forgetting to order those HV coupling caps.
The C1 cap, 140mfd 150 volt 'lytic is the voltage doubling cap that goes to one section of the ballast as a surge limiter.
I'm only going to replace the 'lytics with outboard sections, as the sets aren't that valuable to replace with expensive custom made cans.
More later! Dave, Midwest USA.
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