开云体育

On 2023-02-23 16:24, tom_iphi via groups.io wrote:

In immediate lack of IPA, I have flushed the dead pushbuttons with plenty of ethanol today.
This has worked very well. In addidion, I have repeatedly run a current of 300mA with a current limited power supply
over each switch contact. This really got the on-resistance down. Now, the keys work like a charm again. :-)

Best regards,
Tom DG8SAQ

_._,_._,_

The way you describe it, it is a very dangerous method. Most PSUs have a capacitor over the output connections for stability purposes. Discharging that using a switch gives very high short peak currents which burns away the gold or silver layer on the switch contacts. The resistance will be lower for some time, then increase again much faster and higher than previous. Always use a voltage or current limited PSU with a series resistor to prevent the peak current.
Unfortunately lots of designs also discharge a capacitor directly with a switch, like in reset circuits. Not recommended for professional designs. Always add e.g. 100 ohms in series in such a circuit.

Arie