Mitsubishi VS-60705

[Kevin Mullins]

Been working on a Mitsubishi VS-60705 rear projection screen tv, just about got it rapped up. Had some solder joints and caps on the signal board causing problems.
Already 100 times better. (actually quite nice a picture)

But I'm stuck having some minor black horizontal lines. They run about an 1/8" apart from top to bottom of the screen. They kinda flucuate from a hairline almost gone to about a 1/16" or so wide. They just come and go, but randomly. Almost looking like scanline.
Wasn't sure if I should keep poking on the signal board or maybe power supply section type thing. Most likely a cap if I had to guess.
 
I attached a pic that kinda shows it, hard to capture with a cheap camera.
Ignore the thin white lines, it's the dark ones I'm concerned with.
 
Any pointers or general area to look would be greatly appreciated.

[grantspain]

they look to be almost flyback lines

[Kevin Mullins]

Yeah, I could see the super thin white lines looking like flyback lines......but I don't know why they even showed up in that other pic, you don't see them in person.

I grabbed a much better camera to try and capture what I'm looking at. Of course the pictures were HUGE because the resolution was set so high, so I lost a little clarity compressing them enough to post here. But if you zoom in on a couple you'll see that the lines are perfectly positioned and sized in relationship to eachother. (every other scan line it seems)

It's the black line equally spaced apart lines I'm looking at. They will actually fade in and out rapidly and show a pretty picture when they fade out. It also has an ever so slight vertical jitter. That's what has me leaning more towards a vertical scan/sweep/blanking issue. Like every other scan line is blanking or offset enough to show just black. 

Enjoy the Dora show folks....... lords knows I do ALL the time. 
Cartoons actually work quite well for showing things like this.

[grantspain]

running this via s-video?

[Kevin Mullins]

Just composite at the moment, but I can grab an S-Video cable and try that.

I did fail to mention that this issue is present even with NO signal input.
If I unplug all video sources and just pull up the built in osd menu it's still there.

[grantspain]

Just composite at the moment, but I can grab an S-Video cable and try that.

I did fail to mention that this issue is present even with NO signal input.
If I unplug all video sources and just pull up the built in osd menu it's still there.

ok that rules out what i thought it may be,i am kinda leaning towards the video board atm

[Kevin Mullins]

Yeah, sorry I didn't mention that earlier..... but I've been experimenting so much to rule things out I tend to forget steps taken.

But that's why I was kinda leaning towards the deflection side of things as well. It's like every other scanline is jumping up enough to show a blanking on those particular lines. But it happens pretty fast, but a camera captures it quite well.
Most people in the house don't really notice it unless up real close or I specifically point it out to them. (the picture looks that good consdering the issue) Me..... I've looked at it so much it sticks out like a sore thumb even from 20 feet away now.

I'm probably gonna grab an ESR meter and just keep poking at caps. May just be a voltage regulation problem to an IC or transistor somewhere. The other issues this set had were on the signal board, but I think the deflection stuff is on the main board. I'll have to study the schematics a bit more first though to be sure.

[Kevin Mullins]

After reading this -

Interlaced scanning

To obtain flicker-free pictures, analog CRT TVs write only odd-numbered scan lines on the first vertical scan; then, the even-numbered lines follow, placed ("interlaced") between the odd-numbered lines. This is called interlaced scanning. (In this case, positioning the even-numbered lines does require precise position control; in old analog TVs, trimming the Vertical Hold adjustment made scan lines space properly. If slightly misadjusted, the scan lines would appear in pairs, with spaces between.)

This kinda described what I'm seeing. 

(I think)   

[Kevin Mullins]

Ok, seems running nice bright cartoons made the horizontal lines appear ALL the time.
Decided to watch a regular movie on this set to see what it looked like and noticed it only really showed up on bright screens, highly contrasting objects (i.e. brighter), or when scenes flashed in transition from one to another. So imagine two people, one wearing a light colored shirt and one wearing a dark shirt, the bright one had the horizontal lines the dark one didn't. Or say a dark rainy scene would look great until a lightning flash, then the lines were clear as day.
Brighter colored objects or areas would also have jagged edges, even if the lines weren't showing up very well.
Adjusting the user brightness and contrast controls had no effect on the issue. (but functioned properly)

[grantspain]

somekind of feedback or something with abl circuit-maybe

[Kevin Mullins]

I did go ahead and replace the one common failure cap for part of ABL circuit even though it checked fine. (C2V29)

Been going through with an ESR meter and have found a bunch of bad or open caps.
Most have been in the same general area under metal shielding.
But nothing has made any effect whatsoever on the horizontal line issue or made any change at all for that matter.

It's almost good enough to just call it good, but I'll poke at it some more.