Predicta
 

Well I am unable to fill the bottom. Next?http://tapatalk.imageshack.com/v2/14...4fca8f6b82.jpghttp://tapatalk.imageshack.com/v2/14...6316029c6b.jpg


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Have you replaced the paper and electrolytic capacitors yet in this set? If not, that is the next step. Bad capacitors in the vertical deflection circuitry can cause this.

Other things that could cause this would be a weak vertical output tube, a bad resistor in the vertical circuitry, or a bad potentiometer in the vertical circuitry.

And of course I should check to make sure you know where to find the vertical height and linearity controls on a Predicta -- they are inside the shafts of the vertical hold and brightness controls. Pull the knobs and insert a narrow screwdriver down the hollow shafts of these controls to make adjustments.

Yup. Forgot to mention that it is all recapped. And I have adjusted the side controls with flat blade screwdriver. That is as good as it gets. I have not checked any tubes. I had full screen prior to replacing CRT. I will take back off and check vertical output tube and socket.

Have you rebuilt the couplates? There's two of them that are involved in the vertical: K3 and K4, going by SAMs guide. Otherwise, how does the yoke look? Windings ok?

Good luck with this, your Holiday is better than mine at the moment!

I did a recap a couple years ago. Misplaced my SAMs now I feel somewhat lost. Yoke and windings look great. I am getting closer with a usable set. Thanks for the tips!!

You can download the Sams for free at the ETF: http://www.earlytelevision.org/tv_sc...ms_pw_n-z.html

based on that schamatic 1st thing I would do is check the boost voltage at C3 the check resistance from there to the vert osc.

Have you checked the centering yet?
The two round adjusting screws are on the back of the yoke. If it's too far off center you won't be able to adjust the height and linearity properly.

wow good idea Eric, had not thought of that, esp since he said it happened after changing the CRT.

Old thread here, got delayed by life, will work on tips stated above, thank you all so much!!

My finger pointing to one of back of yoke adjusters you mentioned Eric?

Yes.

No luck with those adjustments. I am going to pull the chassis.

Aha!! Old CRT 2.3 volt. New one is 6 volt. So what do I need to do now?

Probably nothing. It's a series strung filament designed around 117 volts and you likely have 120+ at your outlets.

Back in the day they would short out a section of the big filament dropping resistor. If you have a shorted section, I'd remove the short if possible.

Regardless, the CRT filament isn;t going to cause the problem you have.

Looks to me like the yoke isn't pushed up tight against the CRT or there's an issue with the vertical output circuit.

Makes sense. I am going to try an NOS tube in the vertical output. I am skeptical about the one in it. And I will look at the yoke. See if it will move in further.

The yoke did move in a bit. Good eye!!!! I pulled the chassis and am going to replace the one tube once it arrives. After that I will take prior advice and start measuring voltage.

And redo the couplates as suggested.

Replaced the tested weak vertical output tube with an NOS. Have owned this set for 8 or 9 years and it is performing better than ever. Cell phone pic does not do justice as to how well it is working. Still some more to do to get it where I want, but feeling lucky on the improvement on just replacing a weak tube. I feel comfortable in watching it for a half hour or so now. Next is to replace couplates.

Excellent! I'm glad you got the vertical working properly :thmbsp: