Hi,

I picked up a beautiful Toshiba 27AF46c in mint condition which I will use for retrogaming. I also found the service manual.

This TV has all sort of picture adjustment parameters (vertically, horizontally, trapezium, corners...).

Yet the picture is slightly distorted. the vertical lines are not straight ( (look on the left and right edge of the picture, the vertical lines are convex to the center). Unfortunately corner and trapezium adjustments can't help.

https://i.imgur.com/VNEW0c9.jpg?1

Where does this distortion come from and what is the way to straigthen the picture. Is it usually a service menu adjustment or do I have to adjust something on the neck board.

Thx for your help.

I don't really see what you're describing in the pic (maybe a screenshot of a crosshatch will help), but flat CRTs were rife with all sorts of geometry issues. The bigger they are, the worse the issues become.

I'm not sure a 27" would have any way correction circuitry on board, but you never know. The serv manual will describe any adjustments available.

I think if you just pull the width a bit and add some height, I think it will be as good as it can get.

John

Looks like width is smaller than normal (but you may want it that way for gaming?). and there is a bit of pincushion on the left and right. Look for a pincushion adjustment.
Also, looks like the height is too tall for the width, so if you intend to see the whole raste with a little black all around, decrease the height. Or, if you want no black edges, increase the width.

Thx.
The TV will be for retrogaming in 240p mainly. I will stretch the picture to have a bit overscan.
Still the screen has definitely a geometry problem (or pincushion problem). The service manual is describing only some of numerous parameters but not all. By googling further I found that there is a PARA(bole) setting that may actually help me. I will try it once I will have access back to the OSD which I lost at the moment as I am currently RGB modding the TV.

I will post an update later on.

By googling further I found that there is a PARA(bole) setting that may actually help me. I will try it once I will have access back to the OSD which I lost at the moment as I am currently RGB modding the TV.



Most manufacturers used the same basic chassis on a lot of models, but populated the board depending on things like installed CRT or options such as comb filters, stereo, etc. that not every model was shipped with.

It's not unusual for a TV to show an adjustment in the service menu that does exactly nada, as there are no components loaded on the board to effect.

In any case, if the adjustment shows a decimal or binary number, write it down before adjusting it. Avoid things like horiz freq or HV adjustments.

John

Thanks

I tested the PARAbole and it worked rather well. The geometry is now mainly ok. The result is correct although not as good as my other TV which is a more basic 19" curved Samsung TV.
As a side note I also disconnected the SVM feature (Scan velocity) that tended to make the picture expand when there were too much white (probably a great feature for movies, but not for old gaming). I will give credit for this to SegaHolic from youtube.

https://www.youtube.com/watch?v=1YGy3FuAxfA&t=1388s

ALWAYS write down the original settings so you can go back to first base.
Also be sure you exit the service menu by the book or the settings may not
stay.
Anyhows I see ( I think ) a very slight pin problem & maybe width.
The biggest thing is the bottom half of the pix looks brighter like there
is some vertical fold over. If its there its usually bad caps in the vert.
Post a few more screen shots & a chassis pix. At this time Toshiba went
from there own chassis to one built by Orion / Emerson. That may help.

73 Zeno:smoke:
LFOD !


In any case, if the adjustment shows a decimal or binary number, write it down before adjusting it. Avoid things like horiz freq or HV adjustments.

John

...
The biggest thing is the bottom half of the pix looks brighter like there
is some vertical fold over. ...
73 Zeno:smoke:
LFOD !

Looks to me like camera shutter bar; set is OK if not visible to the eye.