NEC ProSpeed SX/20 disassembly probems

[zoltan]

As this is my very first post on this forum, I would like to say hello to everyone!

So I have been fascinated for quite a while now with late 80s - early 90s portable computers, and recently managed to buy a brand new NEC ProSpeed SX/20 laptop.



As expected, it doesn't work after sitting unused since 1990. After reading some regarding this situation, I think that faulty/dried out capacitors are causing the issue. I managed to disassemble the case, and there seems to be some yellowish residue on the motherboard.



But here is the main problem: I can't find a way to remove the motherboard to be able to see underneath. I unscrewed all the visible screews, I really can't see anything holding it in place, yet I can't lift it out, or can't even wiggle it a bit. Also there are actually two boards on top of each other in the machine, and even a third one betwwen them at some place, it really is packed very tight.



Any kind of help/ suggestion would be greatly appreciated, as even though I am intrigued by these machines, I have almost zero experience working on them. The most I have done was fixing up some Atari Lynx consoles a few years ago, but this machine is a completely different beast.

 

[Adventurer]

A nice machine, but well - it does have a serious capacitor problems.

First - the power adapter is most likely toast (some might work, just to quit later) - you will need another one.

Second - usually there is no need to remove the motherboard on this particular machine (unless you tried to power on the machine without replacing the caps) .

Most issues are in the main power distribution unit, which is covered by a cooling fan. If you really need to remove the motherboard, you need to apply a bit more force when lifting it up - since it sits firmly in a slot underside it. If you need to remove lower part of the board, you will need to unscrew COM and LPT port screws to get it out.

Usually, you need to replace the following caps in power distributin unit for it to work properly - and yes, that includes the tiny, pesky SMD caps as well, which will be leaking all over PCB. Basically you need to replace all brown caps + all SMD caps. While you might start it with replacing brown caps, there will be serious issues with screen flickering/unable to switch the machine on, and failure to detect/charge the battery, including low battery warnings. You will want to replace them.



Good luck, and let us know, when you have finished the repair - I really like this particular machine. Other than caps, hard drive is usually good, and there seem to be no other hardware problems (have repaired several of these machines)...

 

[zoltan]

Thank you so much for the reply!

Now I have an idea at least that the capacitors are indeed the ones to blame. When I will find some time again I will take it apart and see what I can do.
You mentioned that the power adapter is likely toast and I will need a new one. I took that apart too and saw all kinds of capacitors there (but no visible leakage). If I will replace all the caps there, that could be a solution too, or not? I really like the fact that the psu is an integral part of the laptop as it fits nicely under the screen, between the two screen hinges.

You mentioned "usually there is no need to remove the motherboard on this particular machine (unless you tried to power on the machine without replacing the caps)". Well, I tried to power on the machine... Is that an issue? Did I cause further damage with that?