WinBook 486SLC laptop quit posting...

[3lectr1c]

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...

 

[retr01]

Have you used probe(s) to check the continuity of the paths suspected to cause those issues?

 

[3lectr1c]

What paths? What would I suspect? Not Posting is an issue that could be caused by anything There is zero corrosion on the board whatsoever. The main battery was not present and did not leak, and the CMOS battery didn’t damage anything either.

 

[retr01]

There has to be a reason for not posting consistently. Just need to find it. One thing comes to mind is how much power is supplied. All ICs have certain power tolerances. What about the BIOs IC itself?

 

[3lectr1c]

Gotta find it first, shouldn’t be too difficult, it uses AMI. My first suspect is the power board. My IBM PS/Note had similar behavior where it would power on but not POST which was caused by the bad cap. Maybe the caps on that board are out of spec, will likely replace those to start.

 

[retr01]

Like with the compact Macs, "recap anyway!"

 

[3lectr1c]

I'm going to update this thread real quick: It "works" now.
I haven't recapped the DC board yet, but I do believe I need to.

It turns out that the RAM expansion module was improperly seated. I fixed this and it starts again, but after running for a few minutes, it won't boot again if I shut it down. Instead, it displays the symptoms highlighted in the original post. Textbook weak capacitors. It's not on the power supply. I can leave the PSU plugged into the wall, and even into the computer! As long as the power switch on the laptop is switched off, it will get its "recharge time" and boot again after leaving it for 10 or so minutes.

So that's good, but I've got a new problem now. The keyboard ribbon cable has suffered microfractures in the tracks. You can see them visibly if you look through the cable with a magnifying glass, and as such, most keyboard keys do not work, unfortunately including the F1 key required to boot into the BIOS to configure and boot the computer, so I'm stuck.

Well you may say, just use a PS/2 keyboard! Well, I can't. According to the manual, the PS/2 port is for a mouse only! At least, that's how it seems like its worded, and indeed, a PS/2 keyboard won't work on it. If you wanted to use an external keyboard, you needed a special supplied adapter to an old school AT keyboard. I do not have said adapter. Either that or I'm reading it wrong and my port is dead, not sure.

I'm going to attempt to repair the tracks using careful use of an X-Acto knife and some conductive glue that I'm going to order. With any luck, I can repair the keyboard... We'll see.

 

[3lectr1c]

A lot has changed since the last post:
1. I got another Winbook, this time a color model with an SX CPU.
2. I made a section on my website for these, with just about every bit of info you'd need to know about them. Check it out here!

WinBook SLC and SX/DX - MacDat

Specifications, manuals, driver downloads, and more related to the WinBook SLC and SX/DX laptops.

macdat.net