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Thread: ImmersionRC 5.8 GHz 600 mW failure - how to prevent in the future?

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    ImmersionRC 5.8 GHz 600 mW failure - how to prevent in the future?

    I have an ImmersionRC 5.8 GHz 600 mW video transmitter installed in a 250 size racer quad. The transmitter is powered directly from the 3s flight pack. The antenna is connected to the transmitter via a 7 cm RG316 extension cable, and Iím using the stock antenna that came with the transmitter. The video is connected to a Mobius camera using a USB A/V out adapter. Originally, the camera had an internal battery, and I had configured it to not charge when connected to an A/V out cable. This configuration worked fine for more than 20 flights. I bought a super-capacitor pack for the camera so I could power everything from the flight pack and not worry about charging the separate camera battery. I was going to rewire the camera to be powered by a Castle Creations BEC. Without thinking about it, I installed the capacitor pack and powered it up while it was still being powered by the 5V from the video transmitter. Nothing worked. After powering it down, I realized my mistake, and then rewired the camera power to the BEC. When I tested it again, it still didnít work. It was then that I noticed that the heat shrink had melted away right around the chip near the antenna connector. (I believe itís an RF amplifier) When itís powered on, the chip gets too hot to touch.

    Iím assuming that I overloaded the voltage regulator, but the LED still comes on, and the chip thatís hot to the touch is the RF amplifier. So, Iím worried it may have been something else in my configuration. Here are my questions:

    1. What is the failure mode of the voltage regulator? Does it have overtemp or current limiting protection? (many regulators do)
    2. How sensitive are these transmitters to heat? I have mine installed on the middle deck of my quad with very little clearance to the BEC below it. Could it have been caused by an overheat condition? (air temperature was around 75 deg F when it failed, and the props were removed)
    3. Are there any implications in using an RF extension cable on the antenna? Iím using a 7 cm RG316 cable so that I can hard-mount the antenna to the frame and to give me flexibility on where I mount the transmitter.


    I would like to get this transmitter repaired, but I really want to make sure it doesnít happen again.

  2. #2
    ImmersionRC Support Guru swillhide's Avatar
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    1) This unit is good up to 6s so I am sure it wasnt a voltage regulator issue.
    2) They are as sensitive as any other electronic object to heat. If its 110f outside it might not be good to idle it powered for too long, but on a 75f day that will take a bit of time to fry.
    3) Extensions always have some loss but the antenna sets the impedence.

    You do know there is a warranty on this item as long as there is no crash damage or other abuse to it.
    AMA # 1015480 HAM Callsign # Procrastinating..
    Futaba 9c w/Ezuhf /Skywalker 1880 or anything else that I can Lawn Dart.
    Retired: Disco(Sold), Skywalker 1900(Dirt Nap), Qav540g/Nazav2/Iosd mk2

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    The manual states that the regulator can supply up to 300mA. The camera will draw around 500mA when recording, and mine was set up to record when power is detected. So I assumed I damaged it by drawing too much current. But as you said, it's capable of 6s. If you assume the 300mA is at 6s, then for 3s, it should be able to handle 600mA. I'm sure temperature probably plays a role as well, but it wasn't hot when I hooked it up. So I don't know... maybe I didn't fry it and it just happened to fail? I was hoping that someone from ImmersionRC who sees all of the failed units would be able to tell me what happened. (why the amplifier is getting so hot)

    I've been looking into it a little more, and the voltage regulator on the board is a switching regulator. I found the datasheet, and it says that it has overcurrent and overtemp protection. So maybe I didn't kill it after all?

    I bought this one used, so if they'd take it back on warranty, then great. Otherwise, I'd be happy to pay to get it fixed.

  4. #4
    ImmersionRC Support Guru swillhide's Avatar
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    Oh I am sorry I read it wrong as how much can the unit itself handle not how much can it handle being drawn from the unit. 500mA is way over its rated output so you are 100% correct by thinking it died from being over drawn.
    AMA # 1015480 HAM Callsign # Procrastinating..
    Futaba 9c w/Ezuhf /Skywalker 1880 or anything else that I can Lawn Dart.
    Retired: Disco(Sold), Skywalker 1900(Dirt Nap), Qav540g/Nazav2/Iosd mk2

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