Re: 475 With a bowed display. . . .Ideas?


 

On Mon, Aug 10, 2020 at 08:28 PM, Michael W. Lynch wrote:


Raymond,

Unfortunately, the 475 CRT has an extra set of pins on the side of the CRT,
which the 465 CRT lacks. The extra pins are adjacent to and aligned with the
Vertical Deflection plate pins. There is about 1 1/2 - 2 inches between the
two sets of pins (I did not measure, just from memory). So there are a total
of 4 pins on the side of the CRT, where the 465 only has 2 pins. The
Horizontal pins come in from the bottom exactly like the 465. Even though the
465 and 475 are similar, I am much more familiar with the 465 and it is not at
all clear in the schematic or the service manual what these pins do. I am
certainly not experienced enough to say what these are for. These two extra
pins do not show in the schematic, at least not that I can find. I don't want
to risk trying without those extra pins connected. This might damage the
scope, the CRT or worst of all both of them. Clearly different from the
465/465B CRT. Do you have any idea what these extra 2 pins might be for?
I'm not familiar with the CRT of the 475, I have to admit. The extra pins almost certainly are distributed plate connections. In general, there's just a terminator connected between both "ends". I didn't know the 475 had distributed vertical plates. The main idea of distributed plates is to make sure that those electrons that make up the beam at any moment, traveling from cathode to screen at a certain (limited) speed, aren't deflected first to one side then to the other by the same vertical plate('s charge) because they take time to pass the plate which sits along the beam's path for a "significant time". The distributed plate artificially lengthens the signal path and causes the applied signal to travel in parallel with the beam at the beam's speed toward the screen. Using very "short" vertical plates instead isn't an option because deflection sensitivity depends (a.o.) on the time that the charge of a plate works on the beam. You should be able to measure a DC connection between both ends of each distributed plate.

Raymond

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