Need help finding replacement transistors

Discussion in 'The Projects Forum' started by CoolbeaN, Mar 26, 2009.

  1. CoolbeaN

    Thread Starter New Member

    Mar 26, 2009
    9
    0
    I have acquired a flat panel monitor with a bad inverter board (powers the back light). It's pretty obvious that the failure is two transistors that shorted and caused a bank of capacitors to pop. A quick search reveals that this is a common problem with this board and replacing the transistors and capacitors should resolve the issue. I have already replaced the caps but due to a lack of knowledge am having problems finding replacement transistors. Here are the spec sheets on what I need to replace.

    http://www.cheertech.com.tw/Niko-sem/Data sheet\P2804BDG.pdf
    http://www.cheertech.com.tw/Niko-sem/Data sheet\P5504EDG.pdf

    Based on the little research I did, the important specs are:

    V(BR)DSS >= original
    R(DS)ON <= original
    ID >= original

    Based on that I found quite a few chips that should replace the P2804BDG. But I have found no chips based on that criteria that match the P5504EDG. In fact, I am finding very few MOSFETs with a negative
    V(BR)DSS and ID. Mouser has only a handfull and Digikey doesn't list any at all. This leads me to believe that I am missing something and just don't know what I should be looking for. Any help is greatly appreciated.
     
  2. CoolbeaN

    Thread Starter New Member

    Mar 26, 2009
    9
    0
    Ok, I'm still researching. Am I correct in saying that all p-channel mosfets are operating in a negative state but it is just up to the manufacturer whether they list it as a negative or not??

    If that is correct then I should be able to find a replacement. A quick search found some results, but then I got to looking at the rise and fall times. It looks like most of what I am finding has significantly higher rise and fall times. Is this very important?
     
  3. CoolbeaN

    Thread Starter New Member

    Mar 26, 2009
    9
    0
    Still searching. Seems if I can get a chip with enough current handling and fast enough switching then the resistance on is higher than the original.. How much is too much? Where should I compromise?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    P-ch MOSFETs usually have items like Vdss, Id, Vgs and others shown as negative numbers on datasheets.

    Yes, rise/fall times are important. The longer the rise/fall times, the more power will be dissipated in the MOSFET itself.

    You should compare total gate charges as well; the original has 14nC's. The gate driver was probably optimized for the original MOSFET. If the gate charge goes up considerably, it'll stress your driver - and/or cause the MOSFET to dissipate more power.
     
  5. CoolbeaN

    Thread Starter New Member

    Mar 26, 2009
    9
    0
    Last edited: Mar 27, 2009
  6. raduilpig

    New Member

    Jul 17, 2009
    3
    0
    Hello, I have 2 of these boards for repair... monitor - acer 24''(al2416w), so it will be great if we find solution about the problem instead of buy new inverter boards. I will try to find from where we can buy these parts... Good luck!
     
  7. millwood

    Guest

    those are garden variety mosfets. pretty much any mosfets will do. I would try irf510/9510, or similar devices. they are a dollar a dozen.
     
  8. raduilpig

    New Member

    Jul 17, 2009
    3
    0
    ->>
    "CoolbeaN Ok, I think I have found what I need.
    Would this http://www.aosmd.com/pdfs/datasheet/AOD413.pdf be a viable replacement for this http://www.cheertech.com.tw/Niko-sem...5CP5504EDG.pdf ?

    And this http://www.fairchildsemi.com/ds/FD/FDD8451.pdf a valid replacement for this http://www.cheertech.com.tw/Niko-sem/Data sheet\P2804BDG.pdf ?"

    Hello :) , I checked some local stores but I did not find any of these mosfets :( . Can someone tell me from where can I order substitutes of these P2804BDG and P5504EDG :confused: ? I checked IRF510 and IRF9510 as a pair but are they suitable for the inverter board.. (tbd292lf) :confused: ? Please help me with this :rolleyes: , I have two monitors for repair... it will be pity to throw them away...

    Thank you! :)
     
  9. raduilpig

    New Member

    Jul 17, 2009
    3
    0
    Hello guys :) . I found the mosfet pair FDD8451 and AOD413 - the problem is solved, now I have 2 working monitors :) .

    Thank you all! Good luck!
     
  10. Wesley21

    New Member

    Aug 11, 2009
    1
    0
    A couple of questions...

    I too have been looking for a replacement for the recently 'deceased' P5504EDG

    I understand you have had success in replacing the P5504EDG with an AOD413 transistor

    Where can i source a couple of units with reasonable postage charges to the UK?

    Any help would be much appreciated
     
  11. slappav

    New Member

    Sep 23, 2009
    3
    0
    hi. I got the same problem. But the fuse at the power input is also blown (F2 below the blown capacitors). Do anyone know the value of that fuse?
     
    Last edited: Oct 14, 2009
  12. slappav

    New Member

    Sep 23, 2009
    3
    0
    I figured it out. The fuses marked with "K" is 1,5A
     
  13. slappav

    New Member

    Sep 23, 2009
    3
    0
    ok. for those who can't find the parts described in this thread (as I).

    I used replacement transistors named FDD5614P and FDD5612.
    I also had to switch the capacitors.
    Here I used "
    RUBYCON - 35ZLH100M6.3X11 - CAPACITOR, 100UF, 35V".

    And I used a "FUSE, SMD, 1206, 1.5A". However, this is a fast acting fuse, and I think it should be slow. But it works for now =)
    All of these parts can be found at farnell (and is therefore available in Europe).

    Good luck!
     
  14. ewastecomputers

    New Member

    Nov 29, 2009
    2
    0
    i have the same problem with my acer, the screen shows the logo for a sec and then shutdown will replacing the transistors fix this issue the power board is fine and all other circuits seem to be ok i know it is the inverter board, this is a known problem with them. any info would be helpful
     
  15. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I suggest that you replace the electrolytic capacitors first.

    Bad MOSFETs won't damage the caps, but bad caps will likely damage the MOSFETs.
     
  16. ewastecomputers

    New Member

    Nov 29, 2009
    2
    0
    all caps seem fine when i turn on the monitor it stays on for a second then the inverter cuts out. Seems to be the same problem as been described here.But one thing my caps were not effected just the inverter.
     
  17. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Start a new thread.

    Post a schematic.

    Then we can have something to work with.

    Otherwise, this thread is dead.
     
  18. Dead_On_Arrival

    New Member

    Apr 4, 2010
    1
    0
    I don't know if you are still in need of this info but it will help anyone else looking in the UK.

    I found the following links for the original transistors and capacitors needed for the inverter.

    http://www.chsinteractive.co.uk/ele...-mod-p5504edg-general-transistor-ass-make.htm

    http://www.chsinteractive.co.uk/ele...-mod-p2804bdg-general-transistor-ass-make.htm

    http://www.chsinteractive.co.uk/ele...rolytic-105c-low-esr-low-impedance-8x11mm.htm

    Hope this is of help to someone.:)
     
  19. sparky3600

    New Member

    Jun 29, 2010
    1
    0
    Ok Guys,

    Just recently got into fixing monitors.

    Have just got hold of a monitor with this fault as for the mosfets ppl are going on about on this site you can use a FDD6690 and FDD6685 both available from farnell at under £1 each.
     
  20. perfo

    New Member

    Aug 15, 2012
    2
    0
    I stumbled across this post /forum whilst googling to try and find an equivalent for the bad naughty mosfets in my 2416. I like what I read on this here forum so I signed up, especially to say a big thanks to the poster Dead_On_arrival those links are still good and I've got my spare parts on there way. Thanks to all..
     
Loading...