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Can't find replacement mosfets

Discussion in 'Troubleshooting and Repair' started by 500lbkoolaidman, Jan 2, 2012.

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  1. 500lbkoolaidman


    Jan 2, 2012
    I have a Kicker KX600.4 (car stereo amplifier) running 4 channels for my speakers. When installing, I was a moron and had the stereo on, and accidentally touched the positive to an RCA. Two of my channels were making static low volume sound, so I hooked my two other speakers to the two channels that work, but of course, my speakers aren't all playing the music they should be.

    I opened up the amp last night and tested all the mosfets (multimeter on resistance touching the two outer legs) and found two that read less then 10 ohms. All the other mosfets read in the megaohms.



    They read,
    on the left: ON; U1620R; CQ239; KAK
    On the right: ON; U1620; CQ243; AKA

    I can't find replacements online. All I could find is the U1620 for $9. Link to part:

    Anyone know where I can find them or if I can substitute for a more common part? Thanks.
  2. Resqueline


    Jul 31, 2009
    Those are not MOSFET's but rectifiers. What you're measuring is the transformer resistance.
  3. 500lbkoolaidman


    Jan 2, 2012
    Ok, thank you. I believe the test I did is still accurate, they need to be replaced? And do you know if I could replace them with a more common rectifier instead, these specific rectifiers are very hard to find online. I appreciate it.
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    No, they're probably fine -- at least the measurements you're doing (certainly compared to the mosfets) will be pretty meaningless.

    It's more likely that you've damaged a mosfet, but the first thing is to power the thing up and measure the supply rails. Make sure they're OK. Then progress to other stuff (probably starting with the output stage)
  5. 500lbkoolaidman


    Jan 2, 2012
    So it isn't the rectifiers.

    I'm not sure how to test the rails, but I took a guess at it. I plugged everything in and checked the power at each of the speaker outputs. The output that makes bad speaker noise read ~1.75V when all the speaker outputs that sound normal read 0V. Does this give away any hints? Thanks for your patience.
  6. mensah green

    mensah green

    Feb 3, 2012
    kicker 4 channel amp

    hello my name is mensah and i have a kicker kx650 that i got from ebay for 20 dollars ( he told me it was broke) it had the same problem yours have. I dont work at a shop but im pretty good at fixing amps. it was not the refecters it was the Power Transistors that was bad for me i changed those it was good as new ,there are two diffent kind on that amp ,TIP35C and TIP36C , i purchased those from Tayda Electronics, the TIP36C is 91 cents each the TIP35C is 79 cents each, i got a couple extra just in case good luck
  7. 500lbkoolaidman


    Jan 2, 2012
    I ended up selling the amp with one blown channel and buying a much better amp. I tested all the transistors and they all read fine as mentioned, but it still could have easily been a transistor. A bad transistor(s) seems to be the most common problem with amps, it was not a power issue (low voltage, blown fuse, etc.) or anything like that. Nonetheless, I appreciate your help!
  8. Ltlongbarrell319


    May 20, 2021
    I have a kicker xs50 amp I need to know where and I can get replacement mosfets for it and also need just the 6 output frt numbers or even fits that are equivalent to the original ones please and thank u
  9. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    @Ltlongbarrell319 : Do you realize that this is 9 year old thread? Better to open a new thread than to try to revive such a zombie.
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