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Figure 1: A part of the schematic with PLL

This circuit has been implemented on my PCB. However, when I test this circuit (without the DRV135UA), it surprised me that the PLL works except Pin 14 of NE564D (V_PLL). At Pin 14, I did not measure anything. When I disconnect solely Pin 14 from the PCB, whereas other pins are connected to PCB, pin 14 works.

Thus, the question is why does this happen? What kind of possible problems could cause this pin not to work when attached to PCB, but when it is disconnected, it works?

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    \$\begingroup\$ There may be a short on the PCB between V_PLL and GND or C12 may have the short. Power down the circuit and measure the resistance between pin 14 and pin 8. \$\endgroup\$ Commented Oct 8, 2021 at 12:46
  • \$\begingroup\$ Kwok - Hi, (a) I added a link to an NE564 datasheet that I found, to help readers understand the device. (Whenever possible, please include links to datasheets for relevant devices in a question.) However, if you have a link to a better NE564 datasheet, please replace the link I added with that one. (b) Also it might be useful for readers if you can add a photo(s) of this part of your PCB, in case site members see any physical issues. Thanks. \$\endgroup\$ Commented Oct 8, 2021 at 14:08

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