I've been in the process of troubleshooting my Holiday set for the past few days and I'm starting to run out of ideas. I have replaced all capacitors on the main board as well as underneath and also replaced many resistors that I found were out of tolerance. I've checked my work several times now hoping to find a mistake, but my replacememts all look good. My issue with the set is that I cannot get good vertical lock. I've replaced the K4 network and the others with those made by Crist. And the .0015 1000v cap in that area of the board. The set will lock for 10 to 20 seconds then roll for a bit then re lock. I suspected it might have been a weak signal from my blonder tongue, but with a direct hook up it was no better. When I turn the height and vertical lin controls to their minimums I can get hold for about a minute at a time, but it still drifts. I've subbed the 10DE7 and others but no improvements. I haven't touched the 390pf mica cap on the board, and remember bandersontv said that those were sometimes flakey in one of his vids. Shango66 also had poor vertical lock on that barber pole he resurrected, but his fix for it didn't work for mine. This is my first Predicta restore, im stumped, anyone have any ideas?

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Have you checked the tube sockets? Predictas are prone to having internal breaks in the metal parts of the socket. If sync is fed to the vertical grid but the socket grid is open then you'll have no sync to the tube.
Another thing that's worth while is to check the sync waveforms with an oscilloscope....If the sync separator is not opperating properly then there may not be valid signal for the Osc to lock to.

The set will lock for 10 to 20 seconds then roll for a bit then re lock.

If it's doing this on a regular cycle over and over, there's 60Hz hum getting into the vert osc/sweep area, probably ripple on a B+ line. The repeat-rate is the difference beween the mains frequency and vert sweep rate.

Hmm, okey, so maybe I need to go and take a closer look at my Filter Caps and make sure they're correct. I can definitely watch it lock, then slowly retrace lines appear and then it rolls a few times, then usually locks back in. When it's has good lock the retrace lines aren't visible so I assume that means it has good sync when it's there.

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The retrace lines probably appear because it's acting like you are rotating the control , when you rotate the vert holdmonma working set you can get retrace before you hit the point of roll.
Thr control is good ?
I would check the traces and solder joints on the tube socket.