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Slingbox Pro-HD no so go

Discussion in 'Troubleshooting and Repair' started by Luminosity, Sep 1, 2013.

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  1. Luminosity

    Luminosity

    3
    0
    Sep 1, 2013
    I've been given a Slingbox Pro-HD that is not functioning. It powers up briefly (a couple of seconds) and shuts down. These systems are notorious for burning out 470mf capacitors, but the problem I'm having doesn't generally correlate with those caps and they look fine. In a last ditch effort I may try replacing them anyway, but in the attached image I'm curious as to what the tan, square component is (shadowing the pink reset button). It has no markings on it but the pcb has an F1 printed on it. I'm guessing it is a fuse. It gets painfully warm when the system fires up and since it doesn't stay running, cools back down. Based upon the heat, I would love that this is where the problem is, but suspect that something else would be over drawing to cause the heat issue for the fuse to trigger, or is it possible that the fuse could be the problem?
     

    Attached Files:

  2. davenn

    davenn Moderator

    13,589
    1,872
    Sep 5, 2009
    Hi
    welcome to the forums :)

    F1 does indeed indicate a fuse. Its probably getting warm because of the extra current draw elsewhere in the circuit because of the fault condition

    The extra currect drawn just isnt enough to pop that fuse..... you need to be looking at what else may be getting very warm

    Dave
     
  3. Nobody

    Nobody

    12
    1
    Aug 31, 2013
    Here is your fix:

    First change two electrolytic next to switching regulator. they are through-hole. There is a lot of ground around them in led free solder and I believe they forgot to do thermal relieve on their artwork, so you need about 700F iron to get them off.
    Next - delete and bypass thermal fuse FB13, jump it straight trough - they stressed once overheated few times and can't hold current anymore. Don't worry about overcurrent - power supply/adapter will take care of it (if properly rated).

    Wall power adapter might need replacement too. Mine was sagging after only couple of years. I remember that current rating was higher than average, like 3A or so.

    Your welcome.
     
  4. davenn

    davenn Moderator

    13,589
    1,872
    Sep 5, 2009
    that's bad info Nobody ....

    That's a ferrite bead type inductor, part of noise suppression .... it IS NOT a fuse
    along with the other 2 FB's 12 and 14

    Dave
     
  5. Nobody

    Nobody

    12
    1
    Aug 31, 2013
    oops.

    Pardon me, just trying to help, my bad, of course it is common mode choke, not fuse. F1 is fuse. I had to spend more time writing carefully. FB13 cooke to x-leaking current additionally stressing F1. Remove and bypass FB13 AND F1.

    Never the less, my info is good, FB13 is bad, or at least I had them bad more than once. It get shored often. If you already have changed both caps in switcher then get rid of this choke. This is for FCC compliance only anyway.

    And let me stress again: caps are must before anything else. Better get higher temperature ratings and maybe voltage as well - they will last longer this way.

    To make sure you are OK use lab supply. Mine woke up with less than 1A idling after repair and drawing about 2.2A when streaming full HD from antenna. Nothing else gets hot.

    But you know what... just ignore me and keep troubleshooting.

    Good luck!
     
  6. Luminosity

    Luminosity

    3
    0
    Sep 1, 2013
    Thank you. To reiterate and clarify I will remove F1 (apparently an unnecessary fuse) and bypass. FB13 should be removed and bypassed. It appears to be just surface mounted at four points, but if I'm seeing the trace only 2 of those points are actually paths of current or does the bottom pair link with FB 12 an FB14? So I should put a jumper across the 2 active points. If it is 4 active points would the jumpers be across the top and bottom points or the side points? And forgive this following inquiry, if the FB13 shorted, wouldn't that be the same as me putting a jumper in? Additionally, if current is still passing through F1 is it not still functioning or has it weekend to a point that it isn't passing proper current?

    Lastly I'm going to replace the 2 470mfd caps (C26 &C28). I've purchased 35V replacements (originals 25V) I have a couple of 50V I could replace them with, but they are rather old and I'm not sure what all I've put them thru over the years.

    Lastly, FB13 looks challenging to remove or is an iron an wick. the proximity to FB12 and FB14 is very close.

    Thanks again. I've been away from repair work too long. The parts keep getting smaller and they eyes are not what they were when I first started doing this.
     
  7. Nobody

    Nobody

    12
    1
    Aug 31, 2013
    Removal of FB13 should not be an issue, unless you have really pointy and low power iron. I'm guessing hot air station is not and option for you. Wet it with a lot of solder, keep heating both sides while gently prying it with dental hook or small watch screwdriver. It will popup off. Clean pads with solder wick. To jump it, as on your picture, one wire from connector pin 3 to FB14, another wire from connector pin 1 to FB12.
    F1 is only 2 pin, I think you can figure it out how to jump it, you don't even have to remove it.

    I would not say that fuse us unnecessary. PTC fuses are not very reliable, especially when difference between OK and bad is small. I this case 2.5A is OK and 4A is bad. the only reason to use PTCs is the fact that they will self reset, usually don't need to replace them. But over-driven repeatedly they will loose their ratings and will get hot before originally intended.

    If you planing to replace power supply, make sure it is rated not more than 4A, or next time without fuse you might loose some active circuitry, like switcher transistor. If rated under that number - you should be OK as most power supplys nowadays are switchers and will shutdown safely when overloaded.

    If you really paranoid an would like to be super safe - put regular fuse instead of F1, like sloblow 3A or regular 4A. Don't forget next time to check them first.

    Good luck!
     
  8. Luminosity

    Luminosity

    3
    0
    Sep 1, 2013
    I could let my ignorance run endlessly, but for the moment lets keep it simple. If one were to want to replace the PTC fuse, how is one supposed to know what to replace it with if said fuse has no ratings listed on it?
     
  9. Nobody

    Nobody

    12
    1
    Aug 31, 2013
    Empirical/analytical way...

    Normally manufacturer will provide reference to parts marks. In this case I don't know who is the manufacturer.

    Now, you still can find replacement part:

    As I mention I did measure 2.5A at max load. Looking at Digikey list there are HOLD current ant TRIP current for those. I would try 2.5A hold and 4A trip. Here is your part:
    http://www.digikey.com/product-sear...=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

    they are only $0.6 ech + sh.

    Part above will have little to no margin. I guess this is why we have this problem first place with original fuse. If you go with higher hold - power supply probably will trip first. I do not believe this is a problem but probably not the intended way to trip. I jump mine anyway.
     
  10. SLM284

    SLM284

    2
    0
    Sep 27, 2013
    I found F1 Supplier

    My reason for F1 part, is the color, size, and letters on the part - the picture looks the same.

    Therefore my best guess is - Fuse RGEF400 GF400 16V - picture is the same yet sells 100 for $21 USD http://www.aliexpress.com/item/100pcs-1-lot-Fuse-RGEF400-GF400-16V-Free-shipping/907211238.html

    If I use "Fuse RGEF400 GF400 16V" to search with then I find, I can get one or more from Digi-key http://www.digikey.com/product-detail/en/RGEF400/RGEF400-ND/1045839

    I did not look for part FB13 perhaps I can find it, yet I think it should be better quality.
     
  11. SLM284

    SLM284

    2
    0
    Sep 27, 2013
    I did tests and found more information

    From what I found on the internet - reading what a common choke does. You need to research more what one really does. You really do need to install another one - just do not install the same one. Its bad quality therefore use a better one.

    I made one that measures 47 mH and installed it. I made it with 26 gauge wire. I think their Inductor was too thin a wire and blew out or made contact with both sides.

    After testing with this inductor I found it did several things:
    1.) Power Supply connected to wall did not get as hot.
    2.) Board did not get as Hot.
    3.) Picture sharpness increased.
    4.) no interference in picture - it went away.

    From reference guides, it wrote the purpose of a inductor is to store Amperage and prevent or reduce AC voltage and ripple in DC supply. If I use the thought given, that inductors resist change, it reshapes the AC pulse to a DC voltage, that DC passes straight through, That turning it off, it slows down rather than stop abruptly, then acts as storage, it resists change. It therefore can protect sensitive equipment from destructive voltage spikes and high inrush currents. http://www.electronics-tutorials.ws/inductor/inductor.html

    Not sure about the ideal value the inductor should be - common mode choke you refer to.
    It does not seem to matter at this moment. 47mH improved the interference in the picture to where it does not exist, therefore its important to use. I plan to make others to see what near 100mH or other values do.

    This place explains how a choke will reduce the humm in their application therefore will work great in our application too. http://www.300guitars.com/articles/chokes-what-are-they-what-do-they-do/
     
    Last edited: Oct 16, 2013
  12. Nobody

    Nobody

    12
    1
    Aug 31, 2013
    SLM284,

    I'm glad you are digging knowledge on the Interweb, It will make you only better. But one should not be ignorant to specifics of applying such knowledge to real life.

    Little knowledge is a dangerous thing!


    This is very academic description you've found. Nothing wrong with it. In reality, in application like present SlingBox, inductance of these common mode chokes is so small it affects only very high frequency. The purpose of this choke is to eliminate leakage and radiation of high frequency from the box into the air (power cable as antenna). The source of high frequency is high speed digital circuitry on SlinBox's main board. In present case the C.M.Choke is NOT to protect box from power supply interference.

    Radiated emissions measured, according to FCC only above 30MHz. So this choke have to work for these frequencies. No reason to put larger one for lower frequency.

    The link you referring to is for vacuum tube amp, where it is used to reduce power ripple / hum. In new, switch mode power supplies power input ripple reduced through comparing output to reference voltage and high gain negative feedback controlling the output voltage through varying PWM duty cycle of switching pulses feeding pulse transformer and rectifier. (ok, this is pretty academic too). Everything done usually by single little chip.

    Enough with generic info.

    If without this choke you have interference on the picture (probably only from analog inputs, ATSC RF input probably produces clear images), most likely your power brick has problems, and probably with similar caps just like the couple of 470uF on the main board. External power adapter should not produce any high frequency interference. If it does - change caps in it too or get new power supply.

    I'm running SlingBox 300 without common mode choke and without PTC with zero interference on any input.

    And legal disclaimer: I'm not advocating to remove c.m. choke from Box's power input, it is there for a reason (FCC compliance). I'm stating that without, c.m. choke, for the end user, there is no difference if choke is there or not. Oh... even that must be corrected: without this choke your cell phone or radio or TV next to your SlingBox might stop getting clear reception of intended signals, because of coincidental interference, though chance are sooo slim, it is practically nothing.

    Cheers!
    ____________________________________________________________________________________________________
    Trust me, I'm a professional! ;-)
     
    Last edited: Oct 20, 2013
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