22-02-2022, 10:28 AM
Make sure the pull up resistor SIP pack is a 33K or 22K type some keyboards had 4.7K which is too low for reliable operation. To replace this you will need a de-soldering tool, in fact you will need this to remove the key switches as well. The motorised vacuum type is cheap these days. Also I have found the conductive pad becomes non conductive over time and all the cleaning in the world won't make it any better but you can paint it with conductive paint to make it conductive again. Be careful when pulling apart the switch as the spring can fly out. Get yourself an analogue multimeter to check the key switches , a digital one will give false readings as they don't apply much potential to the switch circuit. It is a time consuming job and requires a great deal of patience. If you don't have any experience with a de-soldering tool practice on an old through hole board first, it requires some skill.
I have bought two of these machines back from the dead now and there was more unservicable than faulty key switches, I am an electronics tech of too many decades with a lot of digital experience. The Microbee was dear to my younger self back in the 1980's. I watch all bees coming up for sale for spare bits but they go for too much money for my blood now. Most bees being offered on ebay will have problems due to age, fault finding them is wonderful for the mind. Patience is the key with analytical fault finding techniques. Test equipment should include an oscilloscope as well.
Regards Robert
I have bought two of these machines back from the dead now and there was more unservicable than faulty key switches, I am an electronics tech of too many decades with a lot of digital experience. The Microbee was dear to my younger self back in the 1980's. I watch all bees coming up for sale for spare bits but they go for too much money for my blood now. Most bees being offered on ebay will have problems due to age, fault finding them is wonderful for the mind. Patience is the key with analytical fault finding techniques. Test equipment should include an oscilloscope as well.
Regards Robert