View Full Version : Vertical Centering


VA561
03-02-2017, 09:32 PM
My recent acquisition is a '64 Zenith console, model 7500-4. I don't have the sams yet but I had a question. I was trying to make a few minor picture adjustments and found what I believe is the height control just above the brightness and peak pix knobs behind a door on the front of the set. I went to adjust the vertical centering and on the back of the chassis where it is stamped vertical centering there is just a hole. Nothing else. Where is the vertical centering adjustment? Chassis # 25LC20QS

zenithfan1
03-02-2017, 10:34 PM
Vertical centering is adjusted by pulling those "fishing lines" coming out of the deflection yoke up or down.

Electronic M
03-02-2017, 10:55 PM
Are there two piece of fishing line exiting the yoke? If so those are your centering magnets each line goes to a separate magnet.

zenithfan1
03-03-2017, 12:11 AM
Fishing lines.

VA561
03-03-2017, 07:12 AM
What is the story behind the fishing line setup? Yes there are two "fishing" lines coming from the yoke.

old_tv_nut
03-03-2017, 03:13 PM
Those Zenith models used permanent magnets for centering instead of DC current in the yoke. The fishing lines move the magnets.

VA561
03-03-2017, 08:36 PM
I can move the fishing line on one side. It's like a loop and I can pull one side or the other to adjust the picture. But the other side appears to be broken. Its just one piece of line sticking out. Is there any way to repair the broken side so that I can center the picture? Any help is greatly appreciated. This is a beautiful set with a good picture. I just need to get the vertical centering correct.

consoleguy67
03-04-2017, 08:24 AM
You're right; it is a beautiful set. Once you get the picture centered, please post some screen shots.

Electronic M
03-04-2017, 10:55 AM
You are right about the fishing line having a loose end being an issue. Wish I could help you one that but I've never had to take that mech apart enough to see how it works....IIRC I did have one of those yokes off to de-cat a CRT, but I can't remember looking at the centering mech.

Good luck on it! If that set has a tube amp chassis, and was in a more modern cabinet it would be my ideal combo.:thmbsp:

bluenorm
03-04-2017, 11:22 AM
very nice set :thmbsp:

Penthode
03-10-2017, 07:28 PM
If you remove the yoke and remove the cover, you will find two concentric rings for centering. The fishing line simply is threaded through the ring.

With patience and care, you can easily disassemble and replace the line. I bought my replacement from the sports section of Walmart.

Tubejunke
03-13-2017, 03:17 AM
If you remove the yoke and remove the cover, you will find two concentric rings for centering. The fishing line simply is threaded through the ring.

With patience and care, you can easily disassemble and replace the line. I bought my replacement from the sports section of Walmart.

Well said & good explanation. :thmbsp: