Verticle lines in screen - Videokarma.org TV - Video

Charlie · #1 01-10-2006, 02:11 PM

Hey guys...

Doin some work on my Curtis Mathes roundie. I seem to have things working okay now... still have a few minor adjustments to make. I've noticed some verticle lines on the left side of the screen. They're about an inch from the mask, run from the top to the bottom, and the row of lines is about 1 1/2 inches wide. They're not visible anywhere else in the picture.

Check out the shots below. They're kinda faint in the photos, but still obvious enough that I can see them from sitting across the room.

Has anyone ever seen this or know what causes it?

Charlie · #2 01-10-2006, 02:23 PM

It seems those didn't upload very well. Can barely see what I'm speaking of... tryin again...

jpdylon · #3 01-10-2006, 02:32 PM

looks like a slight wrinkle in the pic. My chromacolor has the same prob. Herringborne pattern perhaps? my CC is solid state, so I don't know how to rid myself of the problem.

Charlie · #4 01-10-2006, 02:36 PM

Wrinkle... that's a good way to describe it!

It's hard to see in those photos. Before I upload them, they look good and you can see the detail. When I look at them after uploading them to AK, it's as if they lost a lot of detail. Maybe it's only on my end... I hope you can see what I'm speaking of.

jpdylon · #5 01-10-2006, 03:28 PM

I have some old troubleshooting guides from around when that curtis was made. i remember reading about wrinkles being the fault of a weakening damper tube. You could try a substitution as well as checking caps in the damper and HO circuits.

I'll look over my manuals again and let you know what I find.

andy · #6 01-10-2006, 06:56 PM

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jpdylon · #7 01-10-2006, 08:46 PM

it does appear to be a slight ringing problem. From what I've read, there are a few things to look for that can be repaired fairly easily:

1. choke(s) in series with the damper are shorted or open (for extreme cases)
2. Damper plate bypass cap is open, or the value has decreased.
3. linearity control (inductor coil) may be mis-adjusted or has drifted off value.
4. Sawtooth peaking resistor has increased in value or bypass cap associated with it has shorted/open.

Other than that, i can't find any othher specific solutions that are relatively simple to fix.

Adam · #8 01-10-2006, 09:08 PM

Do the lines move when the fine tuning is adjusted. I can't really tell from the pictures, but I think those look similar to lines I keep getting on left side of the screen on my Philco b/w. They move when I adjust the fine tuning, I've completely recapped that set, checked all the resistances, and know all the tubes to be good, so it has me stumped. I'm not entirely sure it is a horizontal problem. The only issues I have had with vertical lines caused by horizontal problems was a bright vert. line, as if the picture was compressed, or rather it was scanning too quickly at regular intervals, turned out to be a bad cap.

jpdylon · #9 01-10-2006, 09:23 PM

If the lines are moving when you adjust the fine tuning, one of the IF stage(s) is out of alignment. If they are stable all the time, the problem is most likely in the damper or HO circuitry. I would double check your IF alignment to be sure...

RetroHacker · #10 01-10-2006, 10:38 PM

Seems like I remember reading something about a similar problem in a black and white set - a vertical line running down the left part of the screen. Apparently, it was caused by unwanted oscillation from the horizontal output tube, and that the easy cure for it is to simply swap tubes until you find one that doesn't oscillate in that circuit. I don't know if this interference is the same as the one described in the thing I read, but I do know that the symptom in this case was a vertical line in the left side of the picture. If you have another set with the same HOT, or some spare tubes, try swapping them in and see what happens. Couldn't hurt.

-Ian

Charlie · #11 01-11-2006, 12:43 AM

Guys,

Thanks for the pointers and tips. I'll see what I can find. So far, it seems the lines are stable and don't move with any normal adjustments.

I had changed the flyback over the weekend. Several months ago, something in the cage started doing some serious frying pretty loudly and causing major picture distortion. I assumed it was the flyback and changed it. In fact, I've changed the entire cage and all components... tube sockets, HV leads, caps and resistors... they came from a CM chassis I had that was reworked by CM in 1974. Since then, the frying has stopped... for the most part. Since replacing everything, the same frying sound from the cage has occurred 3 or 4 times in the past two days... but only for an instant... then everything is fine. So, this makes me wonder if the original flyback was actually the problem or not.

I've been watching the set for several hours for the past two days. I've been keeping a constant watch on the HO tube current... cruising fine at 208 ma and the replacement flyback is running pretty cool. The only constant problem right now is the verticle lines at the left. They're not exactly annoying or anything... it's just that they weren't there before.

I had tried a few different tubes in the beginning. At one point, I installed a new damper tube and the plates got really hot really fast... so I put the old tube back in. I'll see if I have some more and swap around to see if the lines go away.

Been watching it tonight for several hours... lines are still there. Everything else in the picture seems good. The convergence could use a slight touch up... but I'll do that once the back is ready to go back on.

Here's a shot from watching my favorite '69 Charger in their recent movie.

bgadow · #12 01-11-2006, 02:12 PM

I had this on a bw Zenith porthole; the area with the lines was compressed, maybe 1/2" or less wide. On that set (much different than this) there was an adjustment (horiz. drive?) that cured it. The typical problem, caused by HO tubes, is Barkhausen (SP?) interference & I've seen this cured by a new tube or I've heard holding a magnet near the tube will work but my luck there has been poor.

Charlie · #13 01-11-2006, 02:21 PM

I've also read about that magnet trick near the tube. Hell... seems like changing the tube would be easier. Later this evening, I'm going to gather a handful of HO tubes and see if I can make a difference with it. I plugged another HO tube yesterday, but it seemed a bit weak as the picture was crunched in fairly well from the sides.

Charlie · #14 01-11-2006, 09:48 PM

Was wondering bout this... Before disconnecting the second anode lead from the CRT, it must be discharged first to avoid doing so with your body (which, by the way, really hurts like hell). Normally there is a healthy arc while discharging it... especially if you do this right after turning off the set.

I'm noticing that there is no arc... no discharge... no nothing when I try discharging the tube... even just seconds after turning the set off. Is this an indicator of something wrong? How else would the charge in the CRT get out?

old_tv_nut · #15 01-11-2006, 11:22 PM

for an example of Barkhausen, see

http://antiqueradio.org/art/hallit-6708.jpg

This comes in through the antenna, and looks ragged. It doesn't seem to be what you have. Have you tried moving some of the wires around - may have something from the horizontal section laying near the video?