vertical lines in a Toshiba TV

[ronl]

That could be what they called "jail bars" caused by a bad cap.Did you change c446? Its in the 178 v source for the video outputs.10uf 250 v.a common problem with fly back winding derived dc power sources.Hope this helps.RonL

[zeno]

Originally Posted by ronl

That could be what they called "jail bars" caused by a bad cap.Did you change c446? Its in the 178 v source for the video outputs.10uf 250 v.a common problem with fly back winding derived dc power sources.Hope this helps.RonL

DITTO
Start with C446. Its an all brand common problem. May as well change it on almost any SS set. Symtoms can be very subtle.

Zeno

[vol.2]

Originally Posted by ronl

That could be what they called "jail bars" caused by a bad cap.Did you change c446? Its in the 178 v source for the video outputs.10uf 250 v.a common problem with fly back winding derived dc power sources.Hope this helps.RonL

Originally Posted by zeno

DITTO
Start with C446. Its an all brand common problem. May as well change it on almost any SS set. Symtoms can be very subtle.

Zeno

I definitely changed that cap. I think I changed basically anything in the power supply, deflection area, and the RGB stuff.

Perhaps I need a better cap than the one I used, but it's a good Nichicon variety. Like I said though in my first post, I think I upped the temperature rating of most of the caps, so that might have reduced the ESR and leakage characteristics of them. I think usually higher temp resistance comes with an ESR hit.

I could try replacing it with a different one, or maybe try monkeying with the value to see if I get a different result.

If so, do you have any suggestions on what to try?

Thanks

Edit: I think it's worth mentioning that I also see the bars if I directly insert an RGB signal into the RGB mux chip on the video processing board. I did this as an experiment to see if I could inject RGB via the mux chip in place of the OSD signal and blank the screen to show a higher quality signal (I succeeded), but I did notice that I was getting the bars in the image this way too. This would leave me to believe that it's nothing about the composite input board or demodulation circuit that is effecting things at least. This set is a Toshiba, so it uses one of their optical isolator chips to get the composite video in without the need for an AC transformer to isolate the set (the optical IC has a separate ground).

[old_tv_nut]

Originally Posted by vol.2

...

Edit: I think it's worth mentioning that I also see the bars if I directly insert an RGB signal into the RGB mux chip on the video processing board. I did this as an experiment to see if I could inject RGB via the mux chip in place of the OSD signal and blank the screen to show a higher quality signal (I succeeded), but I did notice that I was getting the bars in the image this way too. This would leave me to believe that it's nothing about the composite input board or demodulation circuit that is effecting things at least. This set is a Toshiba, so it uses one of their optical isolator chips to get the composite video in without the need for an AC transformer to isolate the set (the optical IC has a separate ground).

If it's not coming in on the previous stages, and all the caps are good, where else could it be but on grounds is what's puzzling me.

I think I would make a quick test of bridging a cap across C446, and triple checking it's the right value, and maybe bridging it to a different ground point on the circuit.

[vol.2]

Originally Posted by old_tv_nut

If it's not coming in on the previous stages, and all the caps are good, where else could it be but on grounds is what's puzzling me.

I think I would make a quick test of bridging a cap across C446, and triple checking it's the right value, and maybe bridging it to a different ground point on the circuit.

C446 was a 10uf, 250V cap @85C. I replaced it with a 10uf, 250V cap @105C, Nichicon brand.

The ground side of the cap was solid and read as close to zero ohms as anything else on the ground plane. I removed the chassis board and made sure to measure it from multiple points on the chassis. The ground is solid.

Edit:

I tried doubling up C446, and I'm not totally sure, but it might have made a little bit of difference. It seems like the bars might be lighter. It may be possible that the original cap was a different value from the Sam's. but honestly, I've run into that too many times, and I always made a spreadsheet of each cap to make sure I put in what came out and note any discrepancies, so I kind of doubt it. Would increasing this cap's value significantly help things? I have a 100uf @250V I could put in there, but I don't want to screw anything up if that might be a mistake.

Do you think I should try sticking the 100uf cap in to see if it helps?

Also, I want to reiterate that this bars issue only shows up in the image of a certain brightness value (and therefore, I would assume voltage value). It's somewhere around 50 IRE I think. If the image is brighter than that, it won't show up, and if the image has bright areas and dark areas, it's only visible in the medium dark areas, and general only really visible in solid colors like you see in most video games.