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WinBook 486SLC Laptop quit posting!

3lectr1c

3lectr1c

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Just arrived from eBay, seems pretty uncommon. Worked perfect when I got it, booted up into Windows 3.1 and besides both shift keys seeming to not work, it was running great. Then I opened it up to remove the CMOS battery, which as I suspected was indeed a Varta pack that had begun to leak down the connector pins. After removing it (no damage whatsoever to the board) I also replaced the floppy drive with a spare that it came with, as the one originally inside it has a bad belt. After this, I put it back together to find that the keyboard no longer worked (I could no longer press F1 to continue from the BIOS). I opened it again to reseat it, and at this point it began to boot inconsistently. Sometimes it would come on and work, keyboard and all. Other times it would start with no keyboard, and other times it would start to a black screen with no POST beep. Unfortunately this third one is now all it does. The power light comes on, HDD light flashes as the drive self tests, suspend light is also briefly lit as it starts before shutting off. Hard disk spins. Any ideas?

There are no obvious cap leaks or bad smells anywhere, though there is some sort of power related board with a few caps, all through-holes that look intact. I'll likely replace them in troubleshooting if I can't get this resolved, but I would like to get this figured out...
 
Oh, and there are no electrolytic capacitors at all in the display assembly. Inverter board and LCD have none. LCD is made by Hitachi, don't open up your display assembly unless you've got busted hinges or vinegar syndrome, I broke a lot of clips along the way the the hinges snapped on the right side.
 
Make sure you don't have "fake tantalums" that are actually elecrolytics in disguise.

You'll also want to desolder those through hole capacitors and look under them, because caps of that age often leak out the bottom and it gets hidden by the base. If you see any wetness when removing the caps, they all need to be replaced.
 
Definitely no imposter caps on the boards. Here’s a shot of the DC board and the motherboard. Pay no mine to the orange residue, it’s degraded glue and hasn’t corroded anything, I checked under it.
F353DCBF-DF5A-4517-B195-B9AD1E7E2539.jpeg
I can see under some of the caps and they look good to me, but I’m really hoping they’ve just gone out of spec and replacing them will bring it back. I hope. Rubycon cap on the right isn’t bulging, camera angle just made it seem that way.
75C4BF91-C3D6-41F6-AB29-C902E4C02788.jpeg
 

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It’s a weird 4 pin plug that I don’t have the pin out for, there’s two voltage lines for power and charge, the pack says that much, I’ll do some probing on it tomorrow to check voltages though. Don’t think it’s bad because it powers on fine, just won’t post, but it could be. I opened it up (it only uses screws thankfully) and internals look fine at a glance, a few Rubycon caps with no obvious leaks. They are old though so I may go ahead and replace them in troubleshooting.
 
I’d think that if main failed it would act as no power (unless I had a battery installed for it to attempt to charge), and if charge failed then it would continue to work fine and just not charge a battery (I don’t have one though). That’s how it works on the PowerBook 500 series AC Adapter which also uses a separate line for charge. Someone rebuilt batteries for their unit and then they wouldn’t charge, charge line on the PSU turned out to be dead. I’ll certainly check though.
 
Got some readouts from the PSU. Both lines should be 16V. One was rock solid 16V, the other around 14V. Problem is I have no idea which is which! It’s worth noting that the PSU has two lights on it, labeled for charge and power. The power light comes on green and the charge light remains off, which makes sense as there’s no battery to be charged. If the 14V line is main power, that could explain my problem. I think the more likely scenario is that it’s the charge line and that it isn’t being started up fully or something like that, and all of this is without any load anyway so it could be pointless to test. I’ll post some photos of the charger tomorrow. Since it can be opened so easily, I wonder if there would be a way to trace the LEDs to the voltage lines. Hmm.
 
Ok folks, promise you won't laugh... I've been a bit of a fool.

The BIOS wasn't properly seated. At least, I now think it's the BIOS. It's the AMI labeled module in the center of the board (see my photo from earlier). I assumed it was RAM module for two reasons:
1. It appears to have memory chips on it
2. There is also an AMI BIOS sticker on a random spot on the motherboard, so I assumed they just stuck it there for some reason.
I guess not. I noticed it didn't look quite seated properly seated upon looking at it from a new angle. After way more force then it should have needed, it popped into place. Immediate POST beep. I've got to reassemble it now, will post a photo when I'm done... Thanks for the advice guys.
 
not so fast... just went back to what it was doing before! ugh!!!!
 
I thought I had it for a second just now, as soon as I disconnected the internal keyboard it worked again. then I tried a PS/2 keyboard and it was recognized (caps lock lights flashed on it) no key inputs would register to enter setup to boot it. then it quit posting again. no idea what's up now!
 
If I spam most keys on the internal keyboard on startup, it gives a keyboard error after it's done posting. F1 doesn't do this, which leads me to believe that it isn't being detected, ugh! That's the one I need for it to boot all the way. And PS/2 doesn't work.
 
num lock works on the internal keyboard but not on the external one. definitely PS2 is dead.
 
1619304E-68A3-43BA-A372-5D60D401D502.jpeg
Are these keyboards really this fragile? Because the exact same thing happened with my IBM PS/Note 425. Bunch of keys stopped working after taking it apart. Only fixed it by replacing the entire keyboard just last night! Is there anything at all I can do to repair it?
 
I had a few problems with membrane keyboards and split traces... I use this to repair them, with a tip of a pin and masking tape. Seems like every vintage natural keyboard I get my hands on needs a repair.

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2pc Silver Conductive 0.2ML Glue Wire Electrically Paste Adhesive Paint PCB Repa | eBay

0.2 ML Silver Conductive Wire Glue Paste for Electronics Trace Repair Application. Apply the silver glue / paste in the place you want. It's perfect for both rigid & flexible substrates. Usually I will respond in 24 hours.
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No clue what happened but I spammed F1 on startup one last time after fully reassembling it and it just randomly worked. I was able to auto detect the hard drive again and it booted right up to windows 3.1. Opened up Word and it seems any key to the left of the 2/w/s/x column doesn't work. What does that conductive glue do? Where do you place it to repair? The keyboard contacts or the connector pins?
 
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