Help needed with first Televisor
Posted: Mon Jan 28, 2019 6:45 am
Hello everybody,
as this is my first post in this forum, let me introduce myself briefly.
My name is Sebastian and I live in southwestern Germany. At work I am an IT administrator, but in the hobby shack I spend my time with audio, video and telecommunications, preferably with technology from yesterday
I am currently building my first mechanical NBTV Televisior and have made good progress so far (I will create a seperate post with the building process, including some pictures, as soon as the device is finished).
I am just left with the following two problems:
1.) It is very hard to get a stable frame sync. The PLL tries its best to get the image stable. The motor accelerates, but then overshoots (the image as it should be is visible for a brief moment). Then the PLL tries to lower the speed, but overshoots again and the speed gets too low. Then it will accelerate again, and overshoot again. With very subtle adjustments of the potentiometer that goes to the motor control PCB and with breaking the motor a bit with the hand, it is possible to get a stable image. But...
2.) there seems to be a problem with line sync as well. The last 4 to 5 (aproximately) lines that should be on the left hand side of the image appear on the right side! This means that the first line that should be on the very right is somewhere in the middle of the image, where the 5th line should be. The whole image is shifted to the left, one could also say.
Now I don't really know what could be the cause of that strange behaviour. Maybe I should mention that I am building a Televisior that's a bit larger than the one described in the handbook, using the club's 15 inch stainless steel disc. My motor is an industrial grade pancake (also called disc rotor) DC motor. I figured it should be a perfect match for a Televisor as it has a very wide voltage range (starts turning already at 3 Volts) and has no cogging like other DC motors do. When the motor has the right speed (means image is in sync), it draws around 300 mA.
I have built the motor control circuit with the values given in the handbook. The only thing I've changed is I omited the 10 Ohm resistor in the positive lead to the motor. With the resistor, the motor didn't get up to the speed required and the resistor got quite hot, despite it being one with 12 Watts of dissipation.
So, if anybody could give me a hint on where to start looking for the cause of my two problems, that'd be great!
as this is my first post in this forum, let me introduce myself briefly.
My name is Sebastian and I live in southwestern Germany. At work I am an IT administrator, but in the hobby shack I spend my time with audio, video and telecommunications, preferably with technology from yesterday
I am currently building my first mechanical NBTV Televisior and have made good progress so far (I will create a seperate post with the building process, including some pictures, as soon as the device is finished).
I am just left with the following two problems:
1.) It is very hard to get a stable frame sync. The PLL tries its best to get the image stable. The motor accelerates, but then overshoots (the image as it should be is visible for a brief moment). Then the PLL tries to lower the speed, but overshoots again and the speed gets too low. Then it will accelerate again, and overshoot again. With very subtle adjustments of the potentiometer that goes to the motor control PCB and with breaking the motor a bit with the hand, it is possible to get a stable image. But...
2.) there seems to be a problem with line sync as well. The last 4 to 5 (aproximately) lines that should be on the left hand side of the image appear on the right side! This means that the first line that should be on the very right is somewhere in the middle of the image, where the 5th line should be. The whole image is shifted to the left, one could also say.
Now I don't really know what could be the cause of that strange behaviour. Maybe I should mention that I am building a Televisior that's a bit larger than the one described in the handbook, using the club's 15 inch stainless steel disc. My motor is an industrial grade pancake (also called disc rotor) DC motor. I figured it should be a perfect match for a Televisor as it has a very wide voltage range (starts turning already at 3 Volts) and has no cogging like other DC motors do. When the motor has the right speed (means image is in sync), it draws around 300 mA.
I have built the motor control circuit with the values given in the handbook. The only thing I've changed is I omited the 10 Ohm resistor in the positive lead to the motor. With the resistor, the motor didn't get up to the speed required and the resistor got quite hot, despite it being one with 12 Watts of dissipation.
So, if anybody could give me a hint on where to start looking for the cause of my two problems, that'd be great!