Creative 5.1 PC speaker system stopped working

Discussion in 'General Electronics Chat' started by seedoflife, Apr 16, 2014.

  1. seedoflife

    Thread Starter New Member

    Feb 2, 2014
    Hi guys, I'm a newbie to this forum and am looking for help to find out what's wrong on a circuit. I have been using the Creative Inspire 5.1 PC speaker system for almost a decade. Sadly it stopped working about a few months back. There is a volume and bass control pod which sits on the desk, and when it stopped working, the green led light on it would not turn on.

    My knowledge in electronics is very limited, but I'm a hobbyist willing to learn. So I took it up as a project to restore this system. Over the last few months I have done the following checks on it and somehow brought it upto some stage where the green light on the volume control pod now turns on. But however, there is no sound output coming from the 5 satellite speakers or the subwoofer.

    Things I have checked and done so far include :

    • Checked the fuse on the circuit - it was ok
    • Checked the power source, which is an external transformer providing AC current at 13.5 volts @ 5 amps - both voltage and amps were good.
    • Checked the DC power conversion stage of the circuit - voltage and amps were good here as well.
    • Proceeded to check transistors, diodes and zener diodes. Found 1 shorted Zener Diode (C11) and two shorted transistors (H945) all of which were promptly replaced - However the green LED light would still not turn on.
    • Then I replaced the op amps (1 4556AD with a 4556D and 5 MC4558CNs with 4558Ds) - still no sign of green light turning on
    • I proceeded to replace the 3 volume control ICs (M51132L) and lo and behold the green light now turned ON. However there was no sound output.
    • Thinking it is something wrong with the 2 audio amplifier ICs (TDA8947J) I have replaced them as well (these were the last of the components leaving aside caps and resistors that i have not replaced on this board). Im still not getting any sound output.

    I think I have hit a wall and am scratching my head all over. Which is why I'm looking to this forum for help. I have noticed that now when I turn on the circuit the highlighted Zener Diode and 4 transistors all go hot within a minute or so (see pictures attached). This so happens to be the Zener Diode that I have replaced which was previously shorted. I am not sure what is going wrong.

    I have seen a previous thread ( with a similar outcome like mine - no green light and no sound. Yet somebody managed to help the OP with his problem. I wish I had that insight to figure out what's wrong here - the kind of knowledge that let you isolate areas of circuit take measurements and figure out which components were bad, rather than having to replace all of them and still get no sound output.

    thanks and regards,
    Metalmann likes this.
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Welcome. Glad I am making new members here. :)

    The knowledge I have is due to the fact that I live and breath electronics and also mainly cause I did study it. :D

    I dunno how I can make some one as good as me like you said but I am not that good. I just fix them.

    I will go thru your post and will reply. Standby
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Inspect ur Board and check and double check for solder bridges.
    You need clean the solder side of the board with a brush and mild alcohol or may be acetone.

    Remove all the IC's. This will eliminate probable shorts if there is a shorted IC. You would need to desolder the soldered ones. Keep the Amp chips desoldered. They can be soldered at the very last minute.

    Third and most important is to check the remote cable for continuity. This will always be the issue in 90% of the time. Take apart remote and check for continuity in every conductor inside the remote cable. You would need to straighten and twist the cable while checking each cable cause then the wire will break and make and show you if it indeed is OK or not.

    We will hit a dead end if the cable is faulty and you did not find. If you get careless and report the cable is OK without properly checking than I wouldn't understand what is wrong with the board.

    I need 100% assurance that the cable is OK or not.
    A faulty cable will result in.
    1. Intermittent power led turning on
    2. No sound.

    Next check if the Zener and transistors still get hot when all the IC's are out of the PCB
    Last edited: Apr 16, 2014
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Looking at the age and complexity of the circuit, and the nasty mess you made of the soldering and massive amount of work that has already been done to no effect, I would suggest scrapping it and just buying a new amp.

    Sorry to be the bearer of bad news. :)
  5. seedoflife

    Thread Starter New Member

    Feb 2, 2014
    Hey guys, update due long time. I managed to get this working. I found out the problem - it was the fault of the cable as pointed out by Rif@@.

    Not wanting to give up, i checked out the other post mentioned above and knew that I should read voltage across the board. When reading the voltage across the volume control IC (M51132L) I found that the volume pin which should be getting a voltage of between 0v and 5.2v, was getting a flat 0v, which made clear why there was no sound output. I checked the spec sheet for this IC and it was quite helpful even for a beginner like myself. I incidentally shorted output to the input and there was sound coming out which clearly indicated that this was a problem with the volume control.

    After carefully testing the cable of the volume control I found that the volume pin was shorting with the ground pin which is why the volume was always 0v. I stripped a few inches of the cable and sure enough found exposed ridges of wire due to maybe twisting and use.

    As of now the circuit is still outside for testing. Hope it works clean and clear as it used to when I re-asseblme the circuit insde the subwoofer cabinet.
  6. wayneh


    Sep 9, 2010
    Well done!
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Job well done.