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Distorted Pismo Screen stumper

Posted by: Sonic Purity on 2015-03-13 17:34:21 I’ve been trying to reassemble at least one working Pismo from a collection of parts able to make one great unit and one functional unit—in theory. The machines belonged to a client/friend, who used them heavily. I did the disassembly, but it was a few years ago. Cutting to the chase, i currently have two nice, functional 500 MHz 1 GB bottom halves, and two unusable screens. One of them is my fault, i know what needs to be done (may or may not work out), and we don’t need to discuss that here. The other one—the one which currently is less worse—is failing in a manner i have not seen before, and don’t know how to resolve. Here is what i know: The defects of each screen stay with that screen and fail the same way on both base units. An external VGA-attached display looks great, with both base units, at the same time the built-in screen looks horrible. The screen in question is from LG and has an LG cable (marked as such)—same one it has had since leaving the factory (i.e. i didn’t mess with it, other than🙂 Contacts at both ends of the data cable have been cleaned. Red, Green, Blue all look correct (Dead Pixel Identifier 5). Gray and white also look correct in DPI5. All look a bit dim, especially white. Identical results across 3 different OS installs (all Tiger 10.4.11) on 3 different hard drives/volumes. Pushing/pulling/etc. on the connectors (at the main board and the display back) and in their general vicinity changes nothing. There is no obvious visual damage to the video cable nor connectors nor screen nor anything else. Here’s a photograph of the failing screen: For reference, here is a camera picture of the external display at the same time: The rainbow pink/blue curvy lines in each photo are a photographic artifact, not visible to the naked eye looking at the screens. Notice how the grays are all messed up in the Pismo screen—seemingly grayscale is reversed, somehow… something like that. Also, there are weird patterns on the Finder folders and strange lines/marks under the title in the top Finder window. I vaguely recall that this particular screen was purchased as a whole top unit, to replace the one in the Pismo the client happened to drive over (i wish i was joking. So does he, but he’s long moved on). I do not recall whether this particular screen ever worked correctly for me/the client. It was purchased from a private party, allegedly working. Anyone seen anything like this? Any idea what the failure mode is? More pertinently, anyone have any suggestions for a fix? Hopefully, ))Sonic((

Posted by: Schmoburger on 2015-03-13 19:22:42 Wish I had an answer to this but unfortunately not the case... just going to follow and hope something comes to the surface. Ive had a similar issue with a Dell CRT I was given. Eventually it got to the point where the display collapsed into unusable smooshed up lines.

Posted by: TheWhiteFalcon on 2015-03-13 19:30:39 You sure it's not an OS install quirk? Or the GPU not being able to drive the OS?

Posted by: techknight on 2015-03-13 19:35:28 If this is an LVDS display ( dont know if it is or not), the gamma correction IC on the t-con likely failed.

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