CTC-5 video video bandpass, chroma ref osc. not running

[CJVx]

Hello again. After successfully completing the SIF, VIF and trap alignments, next on the list would be the video band pass alignment. According to the Sam’s, after setting up all the bias voltages etc. the first step is to make sure the chroma reference oscillator is actually running. It states to measure a cathode of the demodulator tubes with a detector probe, and you should get up to 20 volts. If no voltage is detected, adjust coil A18 until it awakens the oscillator circuit.

Unfortunately, this is not working for me. With a chassis out and everything connected as per requirements, the oscillator does not seem to be running and I’m not able to get it to. Odd thing is, before any of the adjustments the TV did produce stable color so I don’t believe the there are any particular issues with the oscillator, but during the alignment process, it simply is not running for whatever reason.

Any suggestions on this? I am at a roadblock since all the proceedings count on the oscillator operating. I might put the chassis back in and see if I’m getting a color picture, but I would like to figure something out at the moment. Thanks!

[old_tv_nut]

It's hard to imagine what you could have done to stop the oscillator from working if it was OK before.

Have you already played with A18 and accidentally killed the oscillator? If you haven't touched it, I wouldn't disturb it until looking for other problems.

Thoughts:
1) probe is bad somehow?
2) do you have a scope that could be used to see if the oscillator is running instead of the probe?
3) possibility that the crystal has failed?

[CJVx]

Wow thanks, you nailed it with question number one. Something must be wrong with the detector probe I was using, I borrowed the Leader’s detector probe I have been doing my alignments with and sure enough, on my uncalibrated scope I counted just under 1.5 divisions per period at 0.2 µs, the fastest my scope will go. That calculates to roughly 3.57 MHz, all bets are my old uncalibrated scope with minimal resolution at that speed is coming from a bit shy, but this is good news. Going to carry on now with the band pass alignmen.