Testing for failure with a multimeter is only partially effective, whereas a dedicated optocoupler testing circuit provides ...

This circuit can be used to test up to three LEDs at once, connected in series. You can easily increase that number by using a higher supply voltage. If you do so, you should allow 2.7 V for each ...

Dealing with old technology can raise interesting challenges. Whereas modern programmable devices can easily be tested in circuit via JTAG or SPI interfaces, older devices do not have this convenience ...