I've been working on my Toshiba Libretto collection. The plan is to sell off some of my Libretto collection so I only keep *four* of them (interesting 50CT, broken 50CT, perfect 70CT and perfect 100CT). The Libretto 70CT I bought as a parts board is now working and the NiMH battery damage that stopped the RTC circuit from working at all is now fixed with a couple of trace repairs. Thankfully the two vias that were broken still showed light through and a 0.1mm wire could get through to fix them:
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That's by the small resistor and then the trace going underneath the larger "1200" resistor. The most obviously broken part was the test pad on the underside of the board.
The real time clock is now working when I connect a battery to it but I wanted something that's going to last a long time without the risks of a NiMH battery while still fitting in the limited space in this computer. So I got this molex 3-pin microblade connector and put two 1n4148 diodes going [Battery] -> [diode 1 >] -> [diode 2 >] -> [laptop RTC positive] so that it can't charge it and it reduces the voltage to around 2.8v. There's a microblade 2-pin connector on there for connecting up a regular shrink-wrapped CR2032 to fit the vertical height limitation.
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Gonna do this on some more librettos because it means the RTC battery can be replaced without disassembling the laptop further, which otherwise risks breaking the fairly chalky / fragile plastic tabs on the top case these days.
Overall, pretty great since this Libretto 70CT was the worse of the 2, originally I thought there was also a keyboard fault but that ended up being a fault with the keyboard membrane itself. And I just so happened to have a spare good keyboard with bad keycaps, so now there's one bad keyboard with no keycaps and one good keyboard with good keycaps 😀
The Libretto series are so heavily integrated that they fail in interesting ways compared to the Satellite series where the bigger batteries can do more damage. So far I've found that the 70CT's RTC battery functionality can be broken by battery corrosion, but the Libretto 50CT breaks in a far more troublesome way - just like the Satellite 460CDTs that failed because of trace corrosion, the Libretto 50CT's keyboard traces have test pads and those break first. But that's a pretty easy fix, just hook the keyboard connector pins up to the resistor arrays nearby.
Lastly, this Libretto 70CT was so dim. The libretto series I've always thought the display is rather dim but those are usually pretty evenly dim and usable once the CCFL has warmed up. This 2nd 70CT was so dim and unevenly lit that the screen was barely usable outside of a dimly lit room.
For reference, I have somewhere around four bad Sharp LQ61D133 screens that go in the Libretto 50CT / 70CT and wanted to try some things with them. So I went deep into a broken screen, took its backlight assembly apart from the LCD section and fitted an LED backlight in place of the original. Then took apart the good screen and put the broken screen's backlight onto that:
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Honestly I wasn't that impressed overall, the colours looked okay in person but there were some reflections from the LEDs and the camera sees the LED backlight's blue as purple somehow.
Initially I was thinking of trying to retrofit the Libretto's LCD with an LED backlight but there are so many steps involved (led backlight driver needs a 5v > 12v boost converter, there needs to some circuitry to handle different brightness levels, an enable signal etc) that it just wasn't worth it.
Then I took apart the dim LCD's backlight and yeah the CCFL in that was pretty tired, it read 3000 lumens on my Samsung S8's lux meter in the AIDA64 sensors section. And the acrylic light guide had some marks / residue which I think is from the acrylic getting damaged from heat or maybe sparks? Using a magic eraser / melamine sponge to sand back the edge of the light guide that the CCFL fits onto made a huge difference, then putting the 3500 lumen CCFL from the broken LCD made it even better. Putting it all back together the Libretto 70CT with the dim screen is now just as good as the other librettos. Definitely worth doing 😎
Oh also, I think I figured out the connector that the Libretto 50CT / 70CT use for the memory expansion connector, I think it's a bergstak 0.65mm "10169698-70000RLF". Very tempted to grab one from Mouser to see if it fits...