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I have a PTZ camera which has 9-pin USB B device. When I plug into to the USB it shows the error power surge. I knew something was burned out and opened the device to check and found out that one of the rectifier diode right next to the USB input is blown out, unfortunately I couldn't see the markings (value number) on it. I have a basic to intermediate knowledge in electronics working could identify most of the components diode is VD2 in the image:

enter image description here.

I would like to know how to calculate in choose a diode that fits for it. I tried checking online but unable to find. This PTZ camera has both USB and external power supply to work with. USB video transmission and power supply for motors.

Any information or reference would be highly helpful for me.

Update:

Camera is connected through usb 3.0 pcie express card and 12v external power source. While using the camera smoke started coming out and showed an error power surge.

I have removed the diode and it no longer gives me an error but camera also works perfectly. I guess the diode must be regulating voltage Or esd not exactly sure. Which diode and value should I use to protect the camera again with the usb surge.

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  • \$\begingroup\$ Can you provide more info on how/when it failed and can you measure the voltage of both pin of the diode while powered via USB and/or other power source if there are? \$\endgroup\$
    – Julien
    Commented Aug 23, 2023 at 20:20
  • \$\begingroup\$ Given the massive planes it’s connected to and proximity of what I suspect is input barrel connector, TVS or Zener diode. Best case it sacrificed its own life and tripped whatever was feeding it. If it was mine and it’s out of warranty, I would remove it, hook up to lab supply with low current setting and ramp up the voltage. Ideally monitor with thermal camera to check for offenders/other damaged devices downstream. \$\endgroup\$
    – winny
    Commented Aug 23, 2023 at 21:15
  • \$\begingroup\$ @Julien I have edited the question and explained the cause. \$\endgroup\$
    – Ben
    Commented Aug 24, 2023 at 11:51
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    \$\begingroup\$ @winny I have removed the diode and it works fine. Which diode should o replace with and value \$\endgroup\$
    – Ben
    Commented Aug 24, 2023 at 11:52
  • \$\begingroup\$ Good. What's the input voltage to the device? \$\endgroup\$
    – winny
    Commented Aug 24, 2023 at 12:31

2 Answers 2

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First off, if that diode burst, there might be something else that failed on the board. This diode could serve several function. It could be a Zener diode for the voltage regulation, a TVS diode for ESD protection, a power diode to prevent reverse polarity. It's hard to know with that picture.

From the look of it and the white dot, I don't think it is not a transient protection diode. It looks more like a power diode that protect reverse polarity. If so, I would think that any number of Schottky diode that fit the packages could do the trick. If it works without the diode, you might accept to keep operating without it, but if the failure condition occurs (and the device was saved by this diode) again, the device might get broken beyond repair.

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  • \$\begingroup\$ I have updated the question and explained cause in update part \$\endgroup\$
    – Ben
    Commented Aug 24, 2023 at 11:54
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If the marking is "DT" then it may be one of:

  • 6.0SMAJ78CA 78V TVS
  • BZT52H-B10 10V Zener
  • BZX384-C51 51V Zener
  • CD214B-T78CA 78V TVS
  • P4SMA200 171V TVS
  • P6SMBJ78CA 78V TVS
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  • \$\begingroup\$ Marking is not visible as it melted the surface. \$\endgroup\$
    – Ben
    Commented Aug 24, 2023 at 11:55

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