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I have a remote control for a Sharper Image drone. The unit does not power up. The battery power is correct so I open the unit and see that the first component on the circuit board appears to be blown, see attach photo.

After some research I have come to the conclusion that the blown component is a surface mounted diode. The controller runs on 9 volt DC. I suspect the previous owner installed the batteries incorrectly and blew the diode.

The component is very small measuring 1/16th X 3/32nd with tabs at each end. It desoldered from the circuit very easily. What would be the replacement for this component? Where would I get one?

enter image description here

enter image description here

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  • \$\begingroup\$ We can't possibly guess what it was and is a suitable replacement. Perhaps it was a diode, but who knows which parameters it had and why it blew up. The fault that made it blow up can still be present so it may not help if you replaced it with exact same component or better, the replaced componet or something downstream it might then blow up. \$\endgroup\$
    – Justme
    Jan 16, 2022 at 23:02
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    \$\begingroup\$ That's a very tiny diode for the size of the pads it's soldered to. \$\endgroup\$
    – Hearth
    Jan 16, 2022 at 23:03
  • \$\begingroup\$ Does it work without the diode? The datasheet for the LM1117 suggests using an optional diode from vout to vin. The cathode is connected to vin, but it doesn't look like the annode is connected to vout. \$\endgroup\$
    – user57037
    Jan 16, 2022 at 23:14
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    \$\begingroup\$ I don't know exactly what the diode is doing. But it is pretty clear that it is in series with the input to the LM1117 regulator. So I think @Justme is being a little bit too pessimistic. However, it is certainly true that the diode may be a symptom of another fault, so replacing the diode may not fix the board. There is no guarantee that there is only one bad component on the board. \$\endgroup\$
    – user57037
    Jan 16, 2022 at 23:18
  • \$\begingroup\$ Also, I am basically sure it is a diode because it has two pins and a cathode indicator line on it. What else would it be? Doesn't look like a tantalum cap... \$\endgroup\$
    – user57037
    Jan 16, 2022 at 23:21

3 Answers 3

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Yes that diode has died, as per your diagnosis ;)

You can try this: https://nl.mouser.com/ProductDetail/Vishay-General-Semiconductor/SS1FL4HM3-H?qs=lzkR3zxJeCXZvVqMuVBIqA%3D%3D

The footprint seems very big for the used package to me, so the one above should probably fit. Without knowing anything about your circuit, i assumed a maximum reverse voltage of 40V and forward current of 1A should be fine. That 1117 regulator won't like much more than that anyway.

As has been already pointed out, check why this happend if possible. The diode I linked to will be able to take some more abuse I think, so something else might fail instead next power-up

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    \$\begingroup\$ I think this has a decent chance of working. Justme's comment was a bit too pessimistic, in my opinion. The diode is clearly in series with the input of the LM1117, so that gives us a good idea of what the current rating should be, and 40 V should be more than enough. The only think I am not sure about is size. As long as this diode fits I think it will probably work (unless there is something else wrong with the board, which is very possible). \$\endgroup\$
    – user57037
    Jan 16, 2022 at 23:16
  • \$\begingroup\$ nl.mouser.com/ProductDetail/onsemi/… This one is more sized like the original. It's only 30V 0.5A though. Im guessing the other one would fit, really. I soldered big trough hole diodes on SMD pads when I was in a pinch. You'll manage. Edit: its only cents, order both to be sure? \$\endgroup\$
    – Thijs
    Jan 16, 2022 at 23:28
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That diode seems to be smaller compared to the footprint where it is soldered, this maybe the reason why it got damaged. It looks like a 200mW SOD323 diode, probably used to protect against reverse polarity, hence it got damaged with the 9V battery in reverse connection, assuming that your assumption is correct.

Try replacing it with a 500mW SOT123 diode or 1W SMA Diode and see what happens.

enter image description here 200mW SOD323 Diode.

enter image description here 500mW SOT123 Diode.

enter image description here 1W SMA Diode.

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  • \$\begingroup\$ The smaller part could also have had too weak reverse voltage, in which case it will eventually blow over time. \$\endgroup\$
    – Lundin
    Jan 18, 2022 at 14:56
  • \$\begingroup\$ It's definitely not SOD-323, by size comparison with the SOT-223 next to it and the SOT-23 below. SOD-123 seems more likely, and the footprint is likely for either SMA or SMB. \$\endgroup\$
    – Hearth
    Jan 18, 2022 at 15:02
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As noted in comments, that component size does not correspond to the size of the pads. Something larger was meant to be soldered there. This might be the root cause of your problem.

The nearby AMS1117 is a LDO regulator and pin 3 next to the blown diode is VIN. Since the diode has it anode towards that pin, it is very likely one of these options:

  • TVS, or
  • Zener etc part of polarity protection circuitry, or
  • A schottky placed in reverse across the LDO to protect against reverse voltages.

In case of TVS the cathode will be against ground, so you can quickly establish or rule out that with a multi-meter. TVS also tend to be larger packages.

The nearby SOT23 and resistor could possibly be polarity protection circuitry, but this too seems far-fetched given the layout.

So I'm leaning towards the diode being reverse voltage protection, in which case any schottky that can handle the reverse voltage will do. 9V isn't hard to fulfil, most go up to at least 20V.

You need to establish which one of these is the correct answer with a few beeps of your multimeter. It's quite likely that the LDO has been damaged too.

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