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Powerbook 150 - Display Issue

Hi there,

A few month ago i did a restoration of my dads old PB150 including an "upgrading" it to IDE2C, restoring traces and soldering a new PRAM-battery (restoration can be seen here: https://www.reddit.com/r/retrobattlestations/comments/ng5khg ) - the PB 150 after that worked without any problems (ecxept the battery which i did not replace). Yesterday when i tried to start the machine again, after ive had left it alone for a few month i wouldnt get an image on the screen. I hear the chime, backlight seems to work, but i wont get something displayed (sometimes i could notice a black square in the upper right corner.) PB150.jpeg

I read that in some models (PB 140,145,160...) the electrolyte capacitors inside the lcd-unit will get faulty over time so i opened it up an had a look. But the Tantalum (?) Caps look fine to me:



image1.jpeg

I also took a look at the inverter board. C1 and C2 which (to my knowledge) are responsible for contrast and brightness might be not too good, but as far as i know i would still get an image even when both were bad? I would really appreciate to hear from your experience and thank you all in advance.

image0.jpeg
 

3lectr1cPPC

Well-known member
I believe you’ve got some sneaky electrolytics there. The pads are both at one side, a giveaway of that. You wouldn’t be the first person to mistake those for tantalum caps. It looks like they’ve gone bad. You can replace them with ceramics, although they will be extremely tiny.
 

mdeverhart

Well-known member
To the point @3lectr1cPPC made, the ones one the display board are probably electrolytics. If you look closely, you’ll probably see that they’re small cylindrical metal caps inside of a black plastic shell, with the legs of the cap coming out on one end and the cap effectively laying on its side. My Duo had leaky electrolytics in the display that looked just like that.

As noted, you can remove those and replace them with comparable ceramics, which will lay across the two pads. You should be able to find ones that will reach across the pads, but they’ll probably just barely span the gap - they’re really small. There should be pictures around here somewhere, but I can’t find them at the moment.
 

3lectr1cPPC

Well-known member
I recapped a PowerBook 145 screen with ceramics, you can see images of them on this thread where I initially had some problems.
 
I believe you’ve got some sneaky electrolytics there. The pads are both at one side, a giveaway of that. You wouldn’t be the first person to mistake those for tantalum caps. It looks like they’ve gone bad. You can replace them with ceramics, although they will be extremely tiny.
Thank you. And also thank you @mdeverhart & @3lectr1cPPC. I just had a quick look at local sellers here in Germany and to my confusion they caps indeed seem to be tantulums (https://www.reichelt.de/tantal-kond...-0-33-35-p20327.html?CCOUNTRY=445&LANGUAGE=de) - but i guess these should work. I'll probably give them a shot.
 

3lectr1cPPC

Well-known member
The image on that site shows through-hole tantalums, which won’t work to replace those. You’re going to want surface mount style tantalums, although I’d be careful about size. You’ll have to mount them at a different angle for them to fit since the original caps solder points are on one side of the cap. Tantalum caps have the solder points on opposite sides. The ceramics I used were small enough that it wasn’t a problem, but small tantalums should work as well. I can’t check since I don’t know German, but check for the dimensions of the new caps before you order them to make sure they’ll fit.
 
The image on that site shows through-hole tantalums, which won’t work to replace those. You’re going to want surface mount style tantalums, although I’d be careful about size. You’ll have to mount them at a different angle for them to fit since the original caps solder points are on one side of the cap. Tantalum caps have the solder points on opposite sides. The ceramics I used were small enough that it wasn’t a problem, but small tantalums should work as well. I can’t check since I don’t know German, but check for the dimensions of the new caps before you order them to make sure they’ll fit.
Thanks again. Would you mind sharing the measurements of those you used? I guess the got the same values ( 3,3 µF, 35V)?
 
1.6mm long 😬
They are seriously tiny, you’re going to need tweezers and good eyesight to get them soldered in.
Here’s the link I got mine from, but I don’t know if they ship internationally:
Thanks! They ship to my location - unfortunately shipping is almost 20 EUR. Gotta find an alternative ;)

And btw: I just began to desolder the old caps somehow all of them measure just fine - which seems weird to me.
 

3lectr1cPPC

Well-known member
It could always be a different issue as well. It's usually caps, but it could be a bad connection anywhere else as well. If the caps are testing fine, that suggests something else at fault.
 
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