View Full Version : Now that I've got my Zenith 17D20 set working, help with some minor issues?


jmetal88
02-10-2016, 09:18 PM
So, my Zenith 17D20 set, that I've posted about before, is now working and perfectly watchable, but it has a couple of minor issues that bug me a little bit, and I'm not sure if they're just normal for these sets, or if they're issues that would be worth looking into fixing.

The first thing is that there seems to be a bit of a horizontal linearity problem. It's not much, but I can tell things are slightly more stretched out horizontally on the left side of the screen than they are on the right side of the screen. The upper left corner is particularly bad -- I tried adjusting the pincushion correction magnets to see if they could be used to help correct the issue, but I didn't see much improvement. I suspect even if there is a way to sort out the overall linearity issue that that corner will still be distorted.

Second, I've got a couple of audio things going on. One is a buzz during high-contrast images. From what I've read so far, it seems like this is normal for sets using the type of audio detect circuitry that mine has, and since it's honestly not audible most of the time (unless there's text on screen or something) it might be best to just leave that alone. But at the same time, I'm open to suggestions. I've set the buzz control potentiometer and the AGC for the least amount of buzz I can get for the moment, but it's still there on some scenes. The other issue is an intermittent 'crackle' that seems happens at random. This sounds *exactly* like what happens when you turn a dirty volume control up and down, except I'm not touching any of the audio controls when it happens.

Anyway, since this is only the second set I've worked on and I ended up just bypassing the tuner completely on the first one, I'd appreciate anything you more experienced folks could teach me about this.

zeno
02-11-2016, 01:16 PM
Buzz on these Zeniths was common & hard to eliminate.
You can also tweak the quad or detector coil but not much.
The hoz lin problem may be a missing lin sleeve that
is between the yoke & CRT neck. Some techs would pull
it off to get a tad more width.

73 Zeno:smoke:

jmetal88
02-11-2016, 01:30 PM
Buzz on these Zeniths was common & hard to eliminate.
You can also tweak the quad or detector coil but not much.
The hoz lin problem may be a missing lin sleeve that
is between the yoke & CRT neck. Some techs would pull
it off to get a tad more width.

73 Zeno:smoke:

Sleeve is there, but it does have a small tear in it. Could that cause the issue?

old_coot88
02-11-2016, 03:44 PM
Regarding the buzz, have you tried reducing the signal strength?

jmetal88
02-11-2016, 03:48 PM
Regarding the buzz, have you tried reducing the signal strength?

I am not sure how to go about that.

old_coot88
02-11-2016, 04:37 PM
Is the signal going in via a coax and a matching xfmr to the two antenna screws? Or via twin lead to the two antenna screws? If so, try disconnecting from one screw.

jmetal88
02-11-2016, 05:43 PM
Is the signal going in via a coax and a matching xfmr to the two antenna screws? Or via twin lead to the two antenna screws? If so, try disconnecting from one screw.

Yeah, it's coax and a matching transformer. Will give it a shot later tonight and see what happens.

jmetal88
02-11-2016, 06:06 PM
Nah, that didn't really affect the buzz much, other than moving the 'sweet spot' on the buzz control a little bit. Did make the picture nice and snowy, though.

EDIT: Actually that might be a better 'sweet spot' than the one I found originally... Seems to be buzzing on fewer scenes now, even if the amount it buzzes when it does buzz is about the same.

jmetal88
02-14-2016, 04:48 PM
Okay, I took the back off the set and messed with the width sleeve a little more. Pushing it in farther did help the linearity issue, although there is still some of that stretching in the upper left corner. I burned a test pattern DVD to check it out, though, and found the same kind of distortion that exists in the upper left corner of the screen also exists in the lower right corner of the screen. I'm wondering if maybe my deflection yoke is just slightly deformed or something.