A demolition chassis of the German K7N could play this chassis?
The answer is simple no. But we're going to remodel it and start with the power supply and line oscillator. again from the scrap.
This print has someone tried their best to fix it. It was clearly visible that there was a problem with the line oscillator.
In this photo you can clearly see what caused the misery. Nicotine, in the 1970s, people smoked heavily and the layer on it was insane.
So all components off. And mop.
Also, many ceramic capacitors were affected by nicotine and simply not usable.
After this mess we will rebuild.
And then such a print is ready again. Time to test.
Old print out, other old print in.
And look who we have there. That looks like a working line oscillator.
Next print because we are building the second generation K7N, the signal board must also be replaced.
Mounted another print and now see what kind of image comes out...
The 25 volt power supply has a separate transformer. And this transformer has had a collision.
So we send it to a body shop.
And back from the body shop looks neat again.
On the chassis and go.
Time for the wiring.
And of course the low voltage power supply.
Ready time to test see if an image comes out.
A loose selector and see the scoop.
The receiver works but there is something strange. Something 6Mhz comes out of the mf while 5Mhz would be max. But we will come back to this later.
Here's another clear picture.
Of course the test image.
And the channel selector which was used in the German K7N.
No raster print available from a K7N. But the K7 would also work. we just don't use the 25 volt power supply part.
The tubes burn the first sign of life.
And as always you need a line transformer. And those things are always broken.
So just some copper wire.
And winding again.
And then comes the fire test.
The pulses are beautiful.
The booster voltage 500 volts is going in the right direction.
Stepping up the booster.
Voltage looks good.
Test of the line transformer.
Pulses are not quite right.
Under the top coil was another coil that had fallen apart.
Supply voltage from the line output stage works fine.
Replace coil pulses OK.
Booster OK.
Next, test the GY501 filament fire without it plugged in.
Now a full test the high voltage is working. And anything that glows blue is fire. Without smoothing, the high voltage doesn't like it.
A high-voltage cable is sufficient for smoothing. 23 Kilo volts is good for now.
Booster voltage OK.
Just beautiful pulses.
And watch the high voltage work the PD510 Glows beautifully.
Time for a picture tube.
In this case with cabinet.
The first image looks great what a picture.
Color everything just works. Who would have thought that.
Fixed the brightness control. The grid collapsed. PL508 gets boiling hot.
Replacing the coupling capacitor of the PL508. The operating point setting of the PL508 is somewhat vague. Now set with the scope so that the raster saw falls in the middle of the complete supply voltage.
Loose earth strip soldered on signal board. Hum disappeared from picture.
Contrast control does not work.
Replace both BC transistors.
And now it looks like something.
The next problem is the color phase. At the bottom right you see a pink and a beige area in the test image. This should not be colored. this has to do with the invented 6Mhz that we saw at the beginning of this project.
It is not visible on an average color bar. Except for connoisseurs of course.
If you consider that it goes wrong around 4.43Mhz. Does this coil in the mf qualify for it.
The image. After we insert a screwdriver into the core.
And take a look. What happens when you move a screwdriver back and forth in this core.
And this is what happens to the definition of the video.
And here you can see how a miscreant twisted the core out.
After adjustment, this is in the black / white position.
And this in the color mode. The 5 Mhz is muted a bit to reduce interference.
After adjustment, it is noticeable that the pink box is now suddenly no longer colored.
Adjusted the color oscillator a bit. And don't do anything anymore.
