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#1 2014-08-30 19:46:48

Mk.558
Member
Registered: 2014-07-08
Posts: 160

PowerBook Active Matrix Display Tunneling

There have been threads on this subject in other places but I think I can help contribute a little to the general discussion of this problem with images.

Someone here should recognize the PowerBook model I'm using here wink

Here's the scope of the problem. PowerBook models with active-matrix black & white (1-bit) or greyscale displays (usually 4-bit greys, aka 16 greys) displays suffer from darkening of the display corners, working from the outside edges inwards. When the unit is first powered on, there is usually no visible element of the problem initially, especially if it has been sitting for a few days unused. Then after about ten minutes, the issue rears its ugly head.

At the moment, there is no known cure for this problem. Word on the street is that color active matrix displays and passive matrix models are immune to this problem, so far.

By the way, I don't have an Imgur Pro account, so I would suggest some kind of alternative image hosting of some kind if these images are expected to be preserved. I might get an account some day though. (Imgur deletes images if they're not accessed in like 6 months or something. Perhaps a script can be cooked up to skirt around the issue temporarily.)

Let's get right to what we want to see.

First powered on, nothing interesting to see.
H9TGPfRm.jpg

Five or ten minutes later:
j6N5UZjm.jpg

Close up view:
idRrt43m.jpg

You can see if I move the mouse curser into the same corner, the effect is pixel inversion:
O9IxRMIm.jpg

I accidentally activated CloseView in System 6 (yes, System 6 can run on a 140/145/170) and saw a great opportuinity to show some "burn in". Count me surprised on this one.
kZjRpKjm.jpg

I would have never expected the burn-in. I first saw it when the Welcome to Macintosh dialog is shown as part of the boot up process. I don't know if it will get worse with time though like CRTs do. While passive matrix displays have all kinds of funky artifacts (I like them actually, part of the retro-experience), I suppose a display that looks like the following is probably better than one that doesn't work at all:

th_a48a077d.jpg

Admittedly, I haven't seen any examples of *really bad* PowerBook display tunneling, such as a case where at least 3/4 of the display is gone. Maybe this thread ought to produce some.


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#2 2014-09-01 07:51:28

uniserver
Member
From: Sf, Mi
Registered: 2014-05-15
Posts: 955
Website

Re: PowerBook Active Matrix Display Tunneling

thanks for posting this.  Yes this is a pretty serious issue.

I would kind of like to re-approach this issue, instead of regurgitating whatever info might be on other forums.

let's start over fresh.   

So far we understand the issue, and what happens.
We have a good idea of the Models that are effected.
We Do know this is not a capacitor leaking issue.
We are very interested in finding a Definite Cause.
Fixes should only be mentioned if they can be Repeatable and offer at-least an 95% or better level of success.


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#3 2014-09-01 17:02:34

mcdermd
Member
From: Corvallis, OR
Registered: 2014-05-12
Posts: 940
Website

Re: PowerBook Active Matrix Display Tunneling

Is a certain brand or model of panel effected more than another?


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#4 2014-09-01 17:35:12

jt
Member
From: Bermuda Triangle, NC USA
Registered: 2014-05-21
Posts: 1,379

Re: PowerBook Active Matrix Display Tunneling

Great photos, now I understand what's going on with this.

edit: I was thinking about this in the shower  .  .  .

I haven't followed this stuff, but if that were a CRT, not a digital interface, I'd swear that it's a drifting timing value or a problem with the RAMDAC? The only Analog components I can think of offhand in a PowerBook are Brightness and Contrast circuits.

Has anyone looked at resistor failure/drift in the analog circuitry?

Does this only happen in PBs with Analog Video Out? Hybrid Video subsystem?

Last edited by jt (2014-09-01 17:55:03)

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#5 2014-09-01 20:44:55

techknight
Member
Registered: 2014-05-22
Posts: 449

Re: PowerBook Active Matrix Display Tunneling

I still think its crystal contamination from a bad batch of crystals or something of the like. I dunno.

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#6 2014-09-01 20:59:07

Mk.558
Member
Registered: 2014-07-08
Posts: 160

Re: PowerBook Active Matrix Display Tunneling

I don't have a sure-fire list of model affected. Never heard of a Portable with it though, but I've never owned a Portable and have seen only two examples in person.

Haplain would be the man to know. AFAIK he's the Portable expert. I do know it can range from the PB 100 to the 170. 5xx series I have no idea.

EDIT: I like to call it the Free CRT Conversion Kit.

Last edited by Mk.558 (2014-09-01 20:59:32)


SE/30 Cap Replacement http://tinyurl.com/mjf24zs
Classic Mac Networking v3.1 http://applefool.com/se30/
"Linux assumes you know exactly what you are doing." -oboedad55, ubuntuforums.org

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#7 2014-09-01 21:26:31

macdrone
Member
From: Rainier, Or
Registered: 2014-05-25
Posts: 222

Re: PowerBook Active Matrix Display Tunneling

The 180 has the issue also.  I just hot one that does it.

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#8 2014-09-01 21:29:01

macdrone
Member
From: Rainier, Or
Registered: 2014-05-25
Posts: 222

Re: PowerBook Active Matrix Display Tunneling

I wish I had a 5xx with a straight greyscale.  I have not seen the issue in my duos but I may not have them on long enough to tell.

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#9 2014-09-01 23:17:05

techknight
Member
Registered: 2014-05-22
Posts: 449

Re: PowerBook Active Matrix Display Tunneling

I had a Duo that had the tunnel problem. I swapped the LCD out with a color one and said the hell with it.

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#10 2014-09-02 02:59:03

macdrone
Member
From: Rainier, Or
Registered: 2014-05-25
Posts: 222

Re: PowerBook Active Matrix Display Tunneling

We'll sounds like all black and white are suspect minus the portable.  My 5120 is clear as a bell.

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#11 2014-09-02 03:57:34

jt
Member
From: Bermuda Triangle, NC USA
Registered: 2014-05-21
Posts: 1,379

Re: PowerBook Active Matrix Display Tunneling

techknight wrote:

I still think its crystal contamination from a bad batch of crystals or something of the like. I dunno.

I was wondering about crystals, but they pretty much stay the same harmonic no matter what IIRC, it's a physics kinda thing. The support circuitry surrounding the crystal could easily miss a beat however.

Does Passive/Active Matrix have anything to do with it?

Which Duo was it that gave you problems, techknight? Not a 250? The rest are passive matrix IIRC.

The PB100 and 150 are Passive Matrix. Also, neither has a shred of Analog Video Output to FUBAR anything in the Video Subsystem. Are there any reports of problems with that pair??

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#12 2014-09-02 05:05:51

macdrone
Member
From: Rainier, Or
Registered: 2014-05-25
Posts: 222

Re: PowerBook Active Matrix Display Tunneling

My 150 is clear but my 100 but two of my 3 100 screens tunnel.

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#13 2014-09-03 00:08:21

techknight
Member
Registered: 2014-05-22
Posts: 449

Re: PowerBook Active Matrix Display Tunneling

I think it was a duo 270. I made it a 270C.

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