Hello
I have an old 1998 PS/2 keyboard ( = Regular flex circuit "membrane" keyboard ) that has a microprocessor ( black bulb with multiple golden feet ) which tiny feet about 6 out of 46 pcs total are loose. I think this is the fault that the keyboard is not working anymore at all.
-> I used an microscope and saw a glue layer spread though those legs. Some legs are free from that glue probably due to old age 1998. Keyboard used to work few 2-3 years ago.
-> I already used rubber eraser to clean those corroded brown/black connector surfaces to silver colored.
-> Anyone know identify which microprocessor is it and how it functions ? Otherwise the circuitry is very simple and there are only a few components on the flex board.
-> How to glue those legs to the surface and what brand name glue/paste should I use ? I need a tiny pipet or such because legs are 0.5-1.0mm wide and close together.
-> Any advice helps I'm not an professional electronic worker or such. So is this job a total failure ?
Photo of the microprocessor: (RESIZED IMAGE AS A ATTACHMENT BELOW POST)
http://i162.photobucket.com/albums/t278/1231134/20180107_110626_zpskcmho6gc.jpg
Link to my question on other forum:
https://forum.thinkpads.com/viewtopic.php?f=58&t=125361

Germany Siemens Nixdorf PG720p1 1998 All-in-One PC ( Laptop )

Keyboard circuitry data:
TEMIC
321 859
321 700
V26817-B70-V502-02
K7 K8 K9 K0 KN KD
CE AE DF GB

 

Hi 123445, I'd recommend uploading your photographs direct to the forum. I clicked the photobucket link and I was overcome with advertising banners and popups (not pleasant).

Anyway, regarding your question. Keyboards are so cheap that virtually nobody bothers to repair them, so I don't think you're going to be able to find alot of repair support regarding this (not to say that people don't want to help of course!). Apart from the simple membrane/push button inputs every keyboard is different and the implementation of how they work is non-standard.

I know from experience, I have tried to salvage/re-purpose laptop keyboards but finding out what the output is for each key can only be done through experimentation. In the end I gave up because I couldn't justify the time/effort when compared to the value of the keyboard itself.

I'd recommend buying a new one, but if you decide to plod on good luck.

 

"uploading your photographs direct to the forum"

• (RESIZED IMAGE AS A ATTACHMENT BELOW POST)

"with advertising banners and popups"

• Please. Use pop-up and advertise blockers.

"cheap"laptop keyboards"

• It is an external keyboard and a very rare costly one.

 

"uploading your photographs direct to the forum"It is an external keyboard and a very rare costly one.

OK. I can appreciate why you are attempting to repair it, but can't you source a spare keyboard (even for a laptop this old)?. I'm still not optimistic this can be fixed. You will have to somehow remove the black epoxy covering that component to try and expose the ident on the package without removing it with the epoxy (this will be very very difficult), then you might be able to look up the datasheet online.

What others have suggested in other forums is to supply power to the keyboard, press keys and probe the outputs of the flex cable that connects to the motherboard. You will have to do this through experimentation since there are no datasheets with pinouts for things like keyboards.

Can you be sure the laptop itself is OK? Have you have tested it, and are 100% confident that the keyboard is problem and it's not something else (like a software issue). If not perhaps can you connect external peripherals to confirm?

EDIT:
Forgot to ask, does your laptop output have a flex connector or PS2?

 

Hello
See the example video. The removable lid is the external PS/2 keyboard. (All-In-One PC style)
PG710, PG720, PG740,...

• I can use other basic keyboard if I plug the main keyboard's PS/2 connector away.
• I tried to use the PG's own external PS/2 keyboard in another PC and it did not work. So the keyboard itself is faulty and the PG720p1 as a computer runs fine Windows 98.

 

There are lots of PS2 (Some work with PS2 or USB interfaces) on ebay.

Les.

 

"There are lots of PS2 (Some work with PS2 or USB interfaces) on ebay."
Yes I have used a modern usb keyboard with an adapter but this one is a special case because the original keyboard is so nice and functions also as a removable lid to cover the screen.

• So I would like to fix it therefore.

 

As LesJones says above, PS2 keyboards (with built in trackballs) are readily available from eBay. I don't understand why you don't want to just buy a replacement? If you're adamant about saving the keyboard just for completeness then it's alot of effort just for the sake of it. However If this is the case read on.

If there is corrosion on the pins on the connector clean this with IPA and retest just to make sure it isn't just dust/oxide layer preventing a good connection. If the problem persists the next basic troubleshooting technique would be to check for breaks in the cable between the connector and the keyboard (continuity checking with a multimeter).

Try a simple continuity test before tearing the keyboard apart.