CTC-15 line pairing

[DaveWM]

replacing that resistor brought the resistance check amount right in line with sams. Guess now is a good time to go thru the rest.

[DaveWM]

well not sure if there was any improvement, I still seem to get an excess amount of pairing but it does seem like I can dial in and out a little bit with the vert hold.

dont think I will be able to do much more till I get my scope leads fixed. I want to poke around some and look at the vert sync pulse and the b+ for any errant horz hash.

[DaveWM]

more pics

1st is the closeup of the vert sync pulse off the plate of the sync sep tube, this is using a composite video from the converter box injected at the grid of the video amp. this produces a very nice pic, no line pairing or as I have recently read "scan lines".

2nd is using the tuner and a RF signal from the same converter box, this results in "scan lines" that can not be dialed out with the vert hold.

3rd is the grid of the 1st video amp, I prob should have looked at the plate from that to see if the video amp acting up as well, that is the bottom trace, the top is the composite video from the converter box.

[Penthode]

Picture 2 and 3 appear to show differentiated pulses. This would imply poor low frequency response. Vertical sync needs the lower frequency response to work properly.

Perhaps poor low frequency response in the video amplifier is the culprit. It could be due to bad (low capacity) coupling capacitors or open screen decoupling or cathode bypass capacitors.

The RF/IF response could also be the cause: if the video carrier is too low on the nyquist slope of the IF response or if the IF or RF response is not correct, the low frequencies would be attenuated. To check this out, simply adjust the fine tuning control where the color disappears and when the video begins to get a bit smeary. If the interlace improves, that may be it.

[DaveWM]

thx P, I will check it out later. I had to button it up and move it aside for a while.

I have to admit I was tempted to just work in a switch that would allow a direct feed of video and audio, but I prefer to keep it working as orig.