PB190cs odd screen

[RickNel]

The PB190cs that I'm now working on has a strange screen symptom. It powers up, and the screen stays mainly a murky dark green except for the top menu bar and the bottom tab area, which are both normal including showing cursor when it is there.

If I click on a drop-down menu in the visible part of the display, an outline of that menu appears in the dark area of the screen, but no background colour or text content.

I'm cleaning up the logic board at the moment and there has been caps leakage in the little tank farm near the battery connector, so I'm reckoning to replace several caps in that area.

Because backlight and display work normally for those two special parts of the screen, I'm wondering if I might be seeing a video RAM issue? Hope not.

I'm expecting to replace caps in the screen assembly as well. Anyone else experienced that particular screen symptom?

Rick

 

[naryasece]

Might it be an issue with the ribbion cable connecting the display? If you had a known working display (from another 190* or 5300*) you could swap it on, that might help you determine if it is bad video ram.

Any luck with replacing the screen capacitors?

 

[RickNel]

Just got it taken apart and pleased to see only a few electrolytics to replace (though none obviously blown or leaky).

Some evidence that the display had been squeezed (sat upon?) at some point in its history and had a slight curve in it - that could suggest problem with ribbon cable connectors on the side of the screen. When I get the caps replaced I'll try installing a pressure strip on top of the ribbon connections to see if it restores video to that missing region.

I'm reluctant to risk testing the display without fully re-assembling it - I blew up a G4 Lamp logic board once by running tests without full heat-sink contacts in place.

Does anyone have suggestions on how to test screens safely in a disassembled state?

I also have a PB160 with totally dark display, so I'm getting both sets of caps, which may take a while as not all are available where I live.

Rick

 

[oldmacs]

My 5300 and 190 both do this some times!!!!

Its really really weird and powering off and back on usually fixes it.

 

[RickNel]

powering off and back on usually fixes it.

hmmm - that sounds like a caps issue that hasn't yet gone terminal on your machines. Or a PSU maybe not delivering peak amps reliably? While waiting to find the right caps, I'll while away the hours powering my PBs on and off :beige:

Rick