How to fix "vertical lines" on my iMac 27 late 2009

"Since the external video is OK I suspect the cables or connecting points at the end of the cables - if you are certain you have the correct (matching) LCD. Try pressure at the connection points, try moving/rerouting the cables.

If this answer is acceptable please remember to return and mark it."

"HalelujaH!

FIXED!!!

I got a free 27"" IMAC because of this problem! Fix was simple! Boot from MAC osx Snow Leopard CD. Erase and repartition internal hard drive. Install MAC OSX Snow Leopard, then install additional software from folder on install CD. Once install is complete the bars went away!

Presto!

OSX Snow Leopard Install Disk was ordered from Apple for less than $20.00. iMac was donated to local computer recycler that only accepted PCs. So they gave it to me.

Do not upgrade these machines beyond MAVERICKS!

God Bless and God Speed!

Professor out.....TZZZZSSSSSSSSsssssssssssss."

"Georg,

I've read that the vertical lines have something to do with the display card not working. My Dh's computer has the same problem and I'm searching the internet to see if there is anyway to be able to replace it. So far I haven't found anything helpful or significant. I don't think it's fixable w/o you having to take it to an Apple store. Probably done like that on purpose. If I were able to find a way to be able to fix it, I know I could probably do it, since I've replaced the hard drive on one of my older iMac's. -Katia"

"Hello everyone,

since i hadnt gotten a reply soon enough, ive taken this iMac in to my supplier and tested it with a bunch of known-good-parts.

I've swapped the LCD (twice), V-sync Cable, Inverter Board, LVDS cable, even all of these items.

The vertical wavy noisy lines remained visible.

After logically assessing that this cannot be the video-card (digital video artifacts or any other typical GPU related issue generally looks totally different, plus this has a sort of 'analogue-ish' look to it: the lines are like an old CRT-screen that has gone bad, or an old TV that's got bad reception on the coax cable) Ive concluded that it must be the Logicboard, and probably the LVDS connector on the board.

I am pretty darn sure i havent ripped the cable out of the connector when opening up the iMac (i've opened up imacs at least a million times before and know what to watch out for) however, maybe this specific connector had already been played with before and gotten a little sensitive..

just thought i'd let you guys know; i know how darn frustrating it can be to google something that is practically un-google-able (you have to be sort of general in the searchbox, yet specific enough not to get all kinds of bogus results like ads, manuals for decades-old macs, or bulls**t websites) and come up with zero results after spending hours on it.

People need to follow up their questions on here more, and post more in general.

im all for sharing the knowledge, let's keep it up!

oh by the way, in the end, my customer didnt mind the defect and said that she would never even have noticed if i hadnt told her about it.. funny"

Have you tried resetting the P-RAM? Try holding down Command-Option-P-R during power up.

"Hi there, i've seen this several times on different iMac's (all 27 inch models).

It seems it only happens on the models with a v-sync flatcable. The later models with a ""normal"" connector and separate wires seems not to be affected.

At the moment i have an iMac with the same vertical lines with the additional problem that the whole screen goes black after a few days. When i pust the power button 2 times (standby and out of standby) the screen appears again. The external monitor is not affected and keeps playing when the internal scheen goes black.

Already did a reflow of the GPU and changed the inverter board but no difference."