Studiophile DX4 blowing fuses
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Thread: Studiophile DX4 blowing fuses

  1. #1

    Default Studiophile DX4 blowing fuses

    Hi, my DX4's stopped working. Since they're almost 4 years old, I already ordered some AV40's to replace them, but it would be nice to save the old ones...

    They were working one day, and the next they wouldn't power on. I opened it and both fuses were blown. I replaced them and when turned on again, the speakers made a toneful hum, even with the volume all the way down. Then after almost a second the fuses went again. I did this twice.

    The circuit board looks fine. All the tracings are fine and none of the components or chips look damaged. I tested the speakers with my multimeter and they are fine. I saw some older posts saying the amplifiers would need to be replaced and aren't available anymore, but I thought I'd try for help before I giving up and scrapping them.

    Thanks,
    Jon

  2. #2
    Join Date
    Mar 2010
    Posts
    1

    Default

    Same problem

  3. #3

    Default

    I looked closer and noticed that one of the amp chips (a tda2030a) was blown. I ordered some replacements off ebay and will try to fix it. They were cheap, 2$ for 2, but coming from Thailand so it might take a while. I'll let you know if I succeed or fail.

  4. #4

    Default Fixed

    If anyone is interested, I unsoldered the blown chip and put in a new one, replaced the fuses, and the DX4's are working again.

    I will say that the AV40's sound a bit nicer and have the much welcome addition of speaker grills to keep me from poking in the tweeters.

  5. #5
    Join Date
    Oct 2010
    Posts
    1

    Default What type of fuse?

    I went to the local Radio Shack and they had a ton of 250V fuses like the one that had blown in my Studiophile DX4, but I don't know what amperage to use. The blown fuse doesn't specify what amperage. Anyone know what fuse to use?

  6. #6

    Default

    They are 2 amp fuses I believe.

  7. #7

    Default

    This is good info to have. I think this is common with these speakers. I have not replaced the TDA2030A amps yet, but I suspect mine were blown due to the cheap filter capacitors in the power supply. Mine were both swollen at the tops and not looking too healthy. The rectifier looks to be working properly.

    It seems to me that the caps go bad, cause the amps to die and short, which blows the fuses.

    I would recommend to anyone replacing the amps to also replace the capacitors at the same time. They are cheap.
    If you're not sure which ones they are, they are 4700uF and 50V rated, right next to the wires coming from the transformer.

    Please use caution if you're going to replace these - they can probably give you a little shock if you don't short them out before handling the circuit board.

  8. #8

    Default

    OK, guys. After an afternoon of tinkering and scratching my head... My DX4s are working again.

    A couple of helpful hints:

    -Replace the filter caps.
    -I ended up needing to replace the 12V regulator as well (78L12). This little guy runs the input op-amps (4558D) chips. Yours is probably fine. I think I killed mine by accident. I used an alternate part LM7812(available at radio shack which has the reverse pinout and different form factor! Just flip it around and double check the datasheets)
    -I also found that I had to replace a small transistor that switches the speakers off when you plug in your headphones.Replacement part is C1815. This might also have been popped while I was messing around.

    So the list of stuff I replaced is-
    Filter caps 4700uF 25V (I put two 50V caps in - they will last longer)
    Power Amp ICs TDA2030A (only one was blown, but they're cheap)
    12V regulator 78L12 (Radio Shack part is a LM7812C cat no. 276-1771 - remember to install reversed if used)
    NPN Transistor C1815 (Switches headphone on and speakers off)

    All these parts are less than $10. Plus you get to feel better knowing you fixed it yourself!

    Good luck!

  9. #9

    Default

    Quote Originally Posted by jonstar11 View Post
    If anyone is interested, I unsoldered the blown chip and put in a new one, replaced the fuses, and the DX4's are working again.

    I will say that the AV40's sound a bit nicer and have the much welcome addition of speaker grills to keep me from poking in the tweeters.
    hey how exactly did you manage to open up the DX4?? I removed the screws from behind but i dont know how to remove the backplate? any info?? thanks!!

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