Moderators: Dave Moll, Steve Anderson
Andrew Davie wrote:No need for animated GIFs! Video files should work. No file size limits!
Klaas Robers wrote:Harry, it is oscillating ! This is what you see when it is oscillating !
Now increase the value of the capacitor first in steps of 10 x. So make it 10 nF, then 100 nF and you will see that the oscillation stops, far before you reach 470 uF.
Then when this is at say 100 nF, go back in steps of 2, so 47n, 22n. As soon as you see the oscillation starting again, go one step of 2 x forward again. That is the optimal value, then you have the fastest non oscillating amplifier. And you will see that the cross-over distortion also disappeared.
To do this with the horizontal amplifier you need to have video on the screen. Then you run vertical white lines and you see the same effect that you see now, thick lines. And again do the trick with steps of 10 and then back with steps of 2. It is so nice that three steps of 2x equals to one step of 10 x. This is because 2^3 equals to 10..... almost.
Andrew Davie wrote:No need for animated GIFs! Video files should work. No file size limits!
Klaas Robers wrote:Harry, it is oscillating ! This is what you see when it is oscillating !
Now increase the value of the capacitor first in steps of 10 x. So make it 10 nF, then 100 nF and you will see that the oscillation stops, far before you reach 470 uF.
Then when this is at say 100 nF, go back in steps of 2, so 47n, 22n. As soon as you see the oscillation starting again, go one step of 2 x forward again. That is the optimal value, then you have the fastest non oscillating amplifier. And you will see that the cross-over distortion also disappeared.
To do this with the horizontal amplifier you need to have video on the screen. Then you run vertical white lines and you see the same effect that you see now, thick lines. And again do the trick with steps of 10 and then back with steps of 2. It is so nice that three steps of 2x equals to one step of 10 x. This is because 2^3 equals to 10..... almost.
Klaas Robers wrote:I don't know where the spikes are from.
It must be something of 100 Hz hum in the power supply. Am i wrong that I see the spikes to be larger when the vertical scanning is at its beginning / end of the scan? That is when the current through the deflection coils are the largests. That is also when the power supply has to deliver the largest currents.
Harry, you have an oscilloscope. I guess that you see the "spikes" too in the slow sawtooth going to the vertical output amplifier. And then look on the +12 and -12 volt "rail".
But I also see that the "gap" in the vertical scanning is gone with the smaller capacitors.
To start with it is sensible that you make the scannings, horizontal and vertical smaller. There is no need to scanover the size of the screen. So make the scans smaller and place the scans in the centre. I have seen potentiometers in your circuit diagrams to do that.
Klaas Robers wrote:No Harry, it is the other way around. The deflection amplifiers try to make the voltage over the 5 ohm or 2 ohm resistors equal to the input voltage (the sawtooth). If you make the value larger, there is less current in the coil, so the scan is made less wide.
So if you can't make the line short enough, increase the "bottom resistor".
Klaas Robers wrote:Well done Harry, this is something that I recognize as an SSTV-screen. I don't know if the scan speeds are correct, but that can only be seen with modulation of the beam. Then you also have to tackle the synchronisation problem.
Return to Harry Dalek's 5AHP7A Vintage SSTV The Deep image
Users browsing this forum: No registered users and 1 guest