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PET 2001-B-32: problems with the keyboard

Hugofisch

New Member
Joined
Dec 27, 2021
Messages
2
Hi,

my first post in this forum and I hope I find someone who can help me :)

I have here a PET 2001-B-32 with the business keyboard installed. And with this keyboard I have a lot of trouble.
4-5 keys are not working. I cleaned them and tested them with a multimeter tool. I also build
a small breadboard test setup with LEDs to test each connection. But I can't get these 4-5 keys get to work proper again.
Sometimes they have contact, sometimes they don't. All other keys are working fine. And because the keys
are in different rows and columns in the keyboard matrix, I exclude the 6520 as a problem.

On my test breadboard I can get the keys to work, but not very reliable.

I cleaned all contacts with contact cleaner. I also tried to clean the key contacts with sandpaper, but this also didn't work.

Has any of you experience with this kind of keyboard?
Or do you know where I can get/buy an other working keyboard? I searched on eBay, but that was not very successful :)

Thank You for any help.
 

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daver2

Veteran Member
Joined
Jun 19, 2012
Messages
6,801
Location
UK - Worcester
Welcome to VCFED.

There are a number of threads in the Commodore section detailing how to resurrect “awkward” PET keys. I am sure a better-qualified expert will come along presently. In the meantime, perhaps peruse the Commodore threads?

Dave
 

dave_m

Veteran Member
Joined
Feb 2, 2009
Messages
3,345
Location
Southern California, USA
It's probably the rubber/foam keypads that are dirty and non-conductive. Coating it with a conductive pen may help.

See this product from MG Chemicals: https://www.mgchemicals.com/products/conductive-paint/conductive-pens/circuit-pen/

You need to open the back of the keyboard. No need to remove the keys or springs. Also clean the printed circuit board (PCB) with isopropyl alcohol if you wish, but probable not necessary. There are two wires that need to be unsoldered to remove the PCB. Don't forget to solder them when you are done or the shift lock will not work. Try to get the wires where they were (take a photo) but they only go across a switch so it is not critical. Make sure you tighten the many tiny screws when you are done so the PCB will not flex.
 
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Hugofisch

New Member
Joined
Dec 27, 2021
Messages
2
@dave_m and @daver2 Thank You for your replies.
There are no foam or rubber keypads. These switches working with this copper "tongues".
I got the following answer in an other forum (a german one and yes I used the Google translator. Sorry for this :)):
"
I had to re-solder a few contacts on the keyboard PCB of my keyboard and then the 6520, which is responsible for the keyboard, did not work reliably after it got a new socket and then in the end for a new replacement chip (8621) everything has been exchanged, everything works again ... I cleaned the small copper tongues beforehand with contact spray and fine sandpaper ... [...]


In the end, the 6520 was to blame, or rather in combination with the lousy chip socket ...
"

So I will try this now.

Merry Christmas from Germany
Hugofisch
 

Hutch

Experienced Member
Joined
Jul 1, 2018
Messages
199
Location
California
That's very unusual. I've never seen a PET keyboard with those kind of switches. They are always conductive rubber pads.
Is it a 3rd party replacement keyboard?
In my experience, the resistance is important. The switch might light an LED but if the resistance across the switch is more than 1K ohm, the 6520 won't read it, Ideally you want less than 150 ohms.
 

adko

Member
Joined
Jan 7, 2022
Messages
33
Location
The Netherlands
Hi, I'm also new to this nice forum and have the same PET and the same problem
I hope there is a description of this rare keyboard somewhere
Some of the white sleeves on my keyboard are also torn, can these be replaced and bought somewhere?
It seems that the copper tongues are soldered to the circuit board, and that the plate cannot be loosened that way
I'm going to clean everything well and hope to receive more information from someone, or a description
So that I can make this beautiful PET fully working again, because it is already starting up, now the keyboard
Thank you very much, also for using this wonderful forum
Greetings Ad

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