CPD1604S Vertical Collapse

[vol.2]

Originally Posted by Alex KL-1

The IC 604, it follow the truth table in the datasheet? Too busy at moment to analyze it but, a question: perhaps 0V in the pin 1 causes 0V in the outputs?

Yes, IC304 definitely follows the truth table of its datasheet. The incorrect voltage on Pin 1 causes 0V on Pin 5 output.



Pin 1 should be HIGH, and the 4 outputs it controls should all be HIGH, instead it becomes HLHH

So the 2.7V on base of Q613 maybe is the problem. Or possibly the lack of 6.5V on the collector of Q613 causes the 2.7V to appear on the base.

I don't know the chicken or the egg unfortunately


Edit: I'd like to add that I isolated IC250, Pin 10 to try and see where the 23V is coming from that shouldn't be there, and without Pin 10 connected to the rest of the circuit, it no longer has the 23V on it, but I still see 23V all over Q254 and the Vertical Position potentiometer. Not sure why it's wrong, but I also can't see how it's connected to the issue with IC604.