RCA roundie CTC-16 Horiz lock problem

[ws407c]

This one has me stumped. My daily watcher has been running flawlessly for the past year and a half and now the horizontal will not lock in. I noticed just before this happened , the horizontal lock point drifted slowly over the course of a week until the control is out of range to maintain lock. I did slightly tweak the sinewave slug but did not last. I checked the components in the horiz circuit but cannot seem to find anything out of tolerance including the control. Just curious as to see if someone else has had this problem .

[DaveWM]

phase detection diodes ok?

vertical solid lock?

[DaveWM]

if the vert is ok then that clears the sync sep circuit. If both the vert and horz are out, then I would look at the sync sep, and the AGC.

the best way to tell is to scope the output from the sync sep plate, should be a nice clean sync pulse with little video info riding on the top.

[ctc17]

Change the phase detector diodes, they are really hard to test and cause this.
I use high speed Schottky Diodes out of switching power supplies. They will last forever unlike those selenium factory ones.

[ws407c]

Thank you for the fast replies !! I changed the diodes but no change. I figure if I reduce the resistance of R528/544 this will allow me to center the adjustment window. But I would rather try to find out what has changed to produce my problem. I guess I will have to go over it again and pay closer attention. Vertical has solid lock. Again thank you for your quick responses , greatly appreciated !

[ctc17]

Don't start changing values. There is a procedure for setting the coil to center the control. I can send you that if you need it. Sounds like a cap is drifting if the diodes didn't. Solve it.

[ws407c]

Got it! I must be slipping as the problem was a cold solder joint . I am usually very good at finding problems like that but this one was indeed strange. My Daily watcher is now back up and running . I would like the adjustment procedure you mentioned . Thank you for your help !

[DaveWM]

for the record where was the cold solder joint?