Motorola roundie

[Yamamaya42]

Once again, you will be likely finding yourself up the creek without a paddle here (an oscilloscope), with very little to guide you in the right direction, for all you know, the IF could be acting up again, and annihilating the color sync information before it can be processed.

A good start that is IF you had a scope, would be to check the beat pattern going into V22, chroma phase detector, fed from the burst amp, this is what locks in the ref osc.

[timmy]

Originally Posted by Yamamaya42

Once again, you will be likely finding yourself up the creek without a paddle here (an oscilloscope), with very little to guide you in the right direction, for all you know, the IF could be acting up again, and annihilating the color sync information before it can be processed.

A good start that is IF you had a scope, would be to check the beat pattern going into V22, chroma phase detector, fed from the burst amp, this is what locks in the ref osc.

I can’t see how the IF could be the culprit it’s been fine I still have a good b&w picture still it gradually got harder for the color to sync up now it’s gone

[Yamamaya42]

Originally Posted by timmy

I can’t see how the IF could be the culprit it’s been fine I still have a good b&w picture still it gradually got harder for the color to sync up now it’s gone

https://hackaday.com/2018/01/18/know...ideo-waveform/



It's exactly what happened with with my CTC-16XL, I had color with direct input video, but not from tuner, a messed up IF WILL BLOCK color, cause the timings getting to the color circuit will be distorted, in my case, the 4.5 mhz trap was WAY out of tune, blocking all color, leaving a perfect BW screen, the IF on mine is still not fully right, but works well enough.

But yes, a borked IF can distort the colorburst signal timing, leaving just a BW screen, this can be tested by once again removing the 3rd If, and putting in direct video at test point B , as you have done in the past, if you see no color, then it's the color circuits, if you do, then is a problem before the color circuits.

[timmy]

Originally Posted by Yamamaya42

https://hackaday.com/2018/01/18/know...ideo-waveform/



It's exactly what happened with with my CTC-16XL, I had color with direct input video, but not from tuner, a messed up IF WILL BLOCK color, cause the timings getting to the color circuit will be distorted, in my case, the 4.5 mhz trap was WAY out of tune, blocking all color, leaving a perfect BW screen, the IF on mine is still not fully right, but works well enough.

But yes, a borked IF can distort the colorburst signal timing, leaving just a BW screen, this can be tested by once again removing the 3rd If, and putting in direct video at test point B , as you have done in the past, if you see no color, then it's the color circuits, if you do, then is a problem before the color circuits.

The 41.25 trap was the big problem I had originally and never had to mess with the IF in the first place so I can try to tweak the trap and see.