Quote:
Originally Posted by vts1134
Can I use the signal generator for all of the above steps?
|
Sure, absolutely.
Quote:
|
Starting with G1 of the CRT and working back to the detector diode. I'm guessing that anything after the video amp will not give me anything like a picture, but should give me some change in the raster, and anything before the video amp (assuming the failure is upstream) will give me the full pattern. Am I right?
|
Well, when you hit G1 of the CRT (with the genny's output set high enough to see the signal), you should see whatever pattern the genny is set to. It might be negative though (that is, just like a photonegative). As you work back, you should see gain when you hit the grid of the video output stage (pin 7), and attenuating the genny as as needed, more gain at the grid of the 1st video stage (pin 2). This'll confirm that the video stages are working.
As mentioned before, since the detector diode is so easy to get to, i would leave it disconnected as a precaution against zapping it with the probe.
You'll probably see the pattern phase-invert (ie., shift from negative-to-positive) as you work back. That's because a tube's plate is 180 degrees out of phase from the grid. Grid goes positive, tube conducts more, pulling plate voltage down. Grid goes negative, tube conducts less, allowing plate voltage to rise.
oc