Powerbook 160 Screen contrast wont hold

[eric]

Hi all,

I've recapped my 160 screen and inverter board recently and my screen's contrast will just drift all over the place, mostly so low I cant even see it. I've also sprayed contact cleaner into the adjustments which did help a bit, but not anymore.

The behavior is I turn it on, the screen is white but I can bairly make out the startup screen. After about 5 min it'll come down and I will be able to see it. But then after a little bit it the contrast will go out again.

I did try a different PSU and it did seem to help, but only for a bit - still goes to no contrast.

Any other ideas of things to try? the screen looks great when contrast is able to be set correctly.

-Eric

 

[3lectr1c]

What caps did you use on the screen? Ceramics have the potential to lead to this behavior on certain panels.

 

[eric]

Used these for the inverter

https://www.mouser.com/ProductDetail/667-ECE-A1CKS470

https://www.mouser.com/ProductDetail/661-EKRE100ETD330ME0

and tants for the screen.

 

[3lectr1c]

No idea then. Try spraying deoxit into the contrast slider? Check for loose solder joints on the inverter?

 

[Daniel Hansen]

It's possible I suppose the contrast slider itself is bad. Do you have another PB you could swap in the inverter board from? Any one from a 140/145/145b/165/180 will work.

 

[3lectr1c]

It shouldn't be that difficult to test the slider I'd imagine. If you attach a probe to each connector point and measure what I'd assume would be resistance off it. If sliding it results in a steady change, you should be good there.

I do have a 145, so I can verify that we get the same readings if I take mine apart.
Is the 180 inverter the same? I've got images of both and they do look right about identical. I guess it probably is.

 

[eric]

The inverter board says it's only usable for one panel. Measuring the slider inline I get about 186k on one side and 40ohm on the other. The side it's written it slides up to 220k so not sure if it's just due to me reading it inline or what. I'd like to try another inverter board to rule it in or out.

The behavior is so strange though. If I leave it for a day it'll work again for a day. Then the next day it'll never come back. Leave off a day again and it comes back. So strange.

 

[Daniel Hansen]

That's probably a correct reading --- I just checked sliders from a rev b display inverter board I have in a box here, which is different, but comparable for this purpose (157k sliders, read 35Ω to 10kΩ inline). I assume both sliders read the same on yours?

Still, if you're able to swap in another board (if it's from a rev a or c display, i.e. a blue one, CXA-2010 or 2011 --- I'm walking back my inclusion of the 180 board) may help narrow the issue down. The symptom you describe is interesting, and doesn't exactly point at a slider. Thankfully these machines are easy to take apart.

How bad was the cap leakage?