Moderators: Dave Moll, Andrew Davie, Steve Anderson
Klaas Robers wrote:try to insert a square wave of say 10 kHz, 1 volt through a 1M resistor to the input of the preamp. That should become visible at the output of the amp. Any way there should be some output of the preamp, noise, picked up signals, but the square wave is a suitable test signal.
No output: preamp not working,
Yes output, something else not working.
Insert the signal at the target contact, without the vidicon in the deflection yoke.
Andrew Davie wrote:I just watch in the background, in complete awe of your skills. Keep up the good work.
Klaas Robers wrote:Harry, you should realize yourself that if you decrease the deflection current, that you shrink the scanned area of the target, so your picture is made larger..... This is somewhat contra intuitive, but if you realize what you are doing, it is also logically.
This is contrary to a picture tube, where the picure gets smaller if you decrease the deflection currents.
Klaas Robers wrote:When a vidicon is looking at a fixed picture for a long time (days, weeks, months) the picture may be "burned" in the target.
Klaas Robers wrote:Vidicons have no grain, the layer is continuous. But they may have blemishes, spickels and/or unequal dark current (that is wat you see in total darkness, with the hood on the lens) on the target. The sharpness, definition, is almost always good enough for 625 lines.
When a vidicon is looking at a fixed picture for a long time (days, weeks, months) the picture may be "burned" in the target. That is thee dark current in which you still see the previous picture. This is when a vidicon camera is used in a fixed position for surveyance. This disappears slowly (days, weeks, months) when the vidicon is used under changing conditions, or aimed fixed at a white area. So old, used vidicons can have quite some imperfections.
And don't forget, you have TWO focus controls,
- one is the optical focus of the lens onto the target,
- two is the electron beam sharpness adjusted by the current in the focus coil.
Both should be well adjusted.... for 625 lines.
[/quote]Vidicons are not linear, they have a kind of automatic gamma correction. Thsi is contrary to the plumbicons, which are linear. For a plumbicon camera you need a gamma correction circuit, for a vidicon used in the same camera you can switch off the gamma correction.
Good luck!
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