I am expericing difficulties with a simple MIDI output circuit. I have checked the input of the buffer and signal is there. However, there is not signal at ouput. Sketch for MIDI in and out circuit.

At first I thought that I blew up the output buffer so I changed it for a new one. I didn't have the same package available so I fitted a bigger package in the best way possible. enter image description here

Any ideas why the 74LVC1G07 doesn't output signal?

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    \$\begingroup\$ Is the power supply OK? \$\endgroup\$ Commented Mar 16, 2022 at 13:00
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    \$\begingroup\$ The device is open collector - have you provided a load? \$\endgroup\$
    – Kartman
    Commented Mar 16, 2022 at 13:04
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    \$\begingroup\$ Have you connected it to a load to actually see the signal? Shorting pins 4 to 5 on output connector should be simplest way to see the signal at the point you measure. \$\endgroup\$
    – Justme
    Commented Mar 16, 2022 at 14:13

1 Answer 1


MIDI is open collector on the driver side, expecting an opto coupler in the receiver. Schematic and explanation is here. So you need to either plug in the receiver or simulate it with a resistor which you temporarily add. (A 5 pin DIN with an LED from pins 4 to 5 is a useful tool if you work on this stuff much.)

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    \$\begingroup\$ The suggested test with the resistor and LED helped me to find out that one of the leads was not solder properly. \$\endgroup\$ Commented Mar 16, 2022 at 15:54

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