My 540's LCD is afflicted by the gradually darkening corners....I'm confident taking all of it apart and putting it back together, soldering etc...Just need to know what to do if there is any fix besides replacing the LCD (Caps on the Inverter Board and Logic Board look fine.) Thanks for any help.
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Any cure for LCD Tunneling ?
- Thread starter srieck
- Start date
LCGuy
LC Doctor/Hot Rodder
Its a fault with the LCD panel itself...unfortunately there's no fix for it, and it will only become worse as the panel ages. 
And it will happen to every single one of them eventually. (that is, the active matrix B&W/grayscale panels used in the PB170/180 - I've never heard of a passive matrix, or colour active matrix LCD suffering from tunnel vision)
And it will happen to every single one of them eventually. (that is, the active matrix B&W/grayscale panels used in the PB170/180 - I've never heard of a passive matrix, or colour active matrix LCD suffering from tunnel vision)
Bunsen
Admin-Witchfinder-General
That sounds like his fix (on the pb160 at least) is replacing a "40v supply" - does this mean the caps on the inverter board in the LCD assembly? Even if they look ok? Or do I misunderstand what he means ?
As a last resort - If I replaced the motherboard and LCD with one from a 540c or 520b/w would that work or are there other parts that would need need to b swapped as well?
As a last resort - If I replaced the motherboard and LCD with one from a 540c or 520b/w would that work or are there other parts that would need need to b swapped as well?
beachycove
Well-known member
The panel fixed was a passive matrix; it's the active matrix screens that exhibit this blackening behaviour. It is not clear what causes it, but it certainly would be interesting to know if capacitors were to blame.
There are four capacitors on the inverter board of the 540s...they are each fairly isolated and look easy to replace. There's one or two on the main logic board but I don't think those have anything to do with the video circuit.
I'll replace them next week when I've got some time. Nothing to lose.
I'll replace them next week when I've got some time. Nothing to lose.
coius
Well-known member
The inverter has nothing to do with the tunneling, only the backlight. The good news is swapping Active/Passive Color/B&W screens are a cinch to do.
Just swap screen and you would be good to go, don't even need to swap the Mobo.
I did that with mine, and right now I am having an issue with my screens where the lower-half of the screen has alternating Color lines (like one pixels from halfway going down of each: red, green, blue, yellow, white, repeat)
Not sure what causes it, but it's probably the display controller. Doesn't do it on my Black and White Passive-Matrix LCD.
Btw, there is a seller selling the 33Mhz PB 540 Daughter cards on ebay ATM. I just bought one and it cost me $3.59USD shipped. Should be here within the next two weeks.
Just swap screen and you would be good to go, don't even need to swap the Mobo.
I did that with mine, and right now I am having an issue with my screens where the lower-half of the screen has alternating Color lines (like one pixels from halfway going down of each: red, green, blue, yellow, white, repeat)
Not sure what causes it, but it's probably the display controller. Doesn't do it on my Black and White Passive-Matrix LCD.
Btw, there is a seller selling the 33Mhz PB 540 Daughter cards on ebay ATM. I just bought one and it cost me $3.59USD shipped. Should be here within the next two weeks.
techknight
Well-known member
Well mine was the passive matrix. it didnt have the "tunnel vision" it had the VERY dark contrast, and heavy scan-line leakage.
Replacing all the lytics on the panel itself, fixed the problem. had full contrast control, it wasn't drifting around anymore. and the scan line leakage went away with proper contrast.
I just got a powerbook 180 and it has the active matrix screen. So far, no faults reported except for a dim backlight.
But ill check out the panel, recap if necessary.
As far as the color LCD lines issues, Its possible you may need the right LCD cable as well? dont know, never personally had a color powerbook 1xx
As far as the 540, i have the color passive version, and its got the PPC chip in it. but the laptop is physically and cosmetically destroyed so im trying to hunt down a donor in good shape. Almost like someone dropped it off a 2 story building. lol. Sad thing is though, it boots. FDD is toast though.
Replacing all the lytics on the panel itself, fixed the problem. had full contrast control, it wasn't drifting around anymore. and the scan line leakage went away with proper contrast.
I just got a powerbook 180 and it has the active matrix screen. So far, no faults reported except for a dim backlight.
But ill check out the panel, recap if necessary.
As far as the color LCD lines issues, Its possible you may need the right LCD cable as well? dont know, never personally had a color powerbook 1xx
As far as the 540, i have the color passive version, and its got the PPC chip in it. but the laptop is physically and cosmetically destroyed so im trying to hunt down a donor in good shape. Almost like someone dropped it off a 2 story building. lol. Sad thing is though, it boots. FDD is toast though.
coius
Well-known member
Same cable works with the passive greyscale and it works fine. I think it's either the controller on the screen, or possibly a trace/line to the LCD grid has been damaged/broken. But not really sure..
Since the PowerBook hosts this website, I am not incredibly worried as it sits with the screen off. It's been designated pretty much as an old webserver. Seems to run well, even with the DDoS I had several weeks ago. That was fun, but the PowerBook, once I got her back online did well (she crashed within the first few minutes of the attack) and has been having excellent record of run time (as much as close to 142 days non-stop)
Since the PowerBook hosts this website, I am not incredibly worried as it sits with the screen off. It's been designated pretty much as an old webserver. Seems to run well, even with the DDoS I had several weeks ago. That was fun, but the PowerBook, once I got her back online did well (she crashed within the first few minutes of the attack) and has been having excellent record of run time (as much as close to 142 days non-stop)
So then it seems the actual "tunneling" issue (gradual darkening of the corners after the computer has been on awhile) as opposed to contrast issues (like techknights) is - as far as we can tell - most likely an issue with the LCD screen in specifically active-matrix/greyscale like the 540(nonC) ?
If this is the case, putting another active-matrix/greyscale screen in there is not really a fix as all of them will eventually have this issue.
I wonder what would happen if I put a passive-matrix lcd (from a 520) in there (either nothing or it might function like a 520?) ....or maybe even a color active from a 540c ? (I know it would only display greyscale if it even worked.)
Or do the exact logic boards need to match the exact lcds for the 520,520c,540,540c,550c respectively ?
Are we pretty convinced tunneling can not be related to caps ?
Has anyone seen the tunneling issue on anything other than an active-matrix/greyscale lcd ?
If this is the case, putting another active-matrix/greyscale screen in there is not really a fix as all of them will eventually have this issue.
I wonder what would happen if I put a passive-matrix lcd (from a 520) in there (either nothing or it might function like a 520?) ....or maybe even a color active from a 540c ? (I know it would only display greyscale if it even worked.)
Or do the exact logic boards need to match the exact lcds for the 520,520c,540,540c,550c respectively ?
Are we pretty convinced tunneling can not be related to caps ?
Has anyone seen the tunneling issue on anything other than an active-matrix/greyscale lcd ?
beachycove
Well-known member
There are posts here and there on various lists and such about the tunnelling issue that go back some years, which has led me to think that caps are most likely unrelated to the problem — but who knows until it's tried?
The problem appears to be restricted to the first B&W/Greyscale active matrix screens (the "glassy" ones). Not all of them are affected, as on many of these old machines, there is still no sign of it. Maybe a technical flaw in manufacturing/ different branded components in the various machines in question?
The problem appears to be restricted to the first B&W/Greyscale active matrix screens (the "glassy" ones). Not all of them are affected, as on many of these old machines, there is still no sign of it. Maybe a technical flaw in manufacturing/ different branded components in the various machines in question?
both my 180s had it when I first got them. but both were stored in un-heated locations and it was mid winter, so they were way cold when I first got them... Once they were inside for several days it cleared up...
maybe try putting it in the freezer for a few days? I know totally random idea, but who knows maybe it'll work. (be really cool if it did)
maybe try putting it in the freezer for a few days? I know totally random idea, but who knows maybe it'll work. (be really cool if it did)
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