Help on JVC EX-TD55R - no sound

Discussion in 'Electronic Repair' started by Bruno Willi, Aug 1, 2003.

  1. Bruno Willi

    Bruno Willi Guest

    Hi,

    my JVC EX-TD55R (a compact stereo system) works fine, just without any
    sound coming out...

    There are two relays on the amplifier-pcb. The always 'clicked' when
    the thing was switched on - no they keep silent. There are some big
    capacitors (2x 2200µF, 2x 3300µF) - could they make the problem?

    Maybe someone can send me schematic of this compact system, it would
    help me a lot.

    Bruno
     
    Bruno Willi, Aug 1, 2003
    #1
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  2. Bruno Willi

    Sofie Guest

    Bruno Willi:
    If you are thinking that the "some big capacitors....." are causing the
    symptoms you are reporting with the JVC stereo system then I am just about
    certain that the schematic will not be of any help to you. A schematic is
    only most helpful to experienced and knowledgeable techs with the proper
    test equipment, tools and replacement parts..... there are no step by step
    troubleshooting instructions on the schematics or manual that will offer
    much help to the novice.
    There is a lot of troubleshooting that can be done right now without the
    schematic..... Most shop techs fix the majority of equipment without the
    expensive and sometimes hard to obtain service manual and schematic.
    Certainly the PS is a good place to start but it is quite unlikely that the
    big capacitors are bad..... more than likely there are other components
    such a open resistors, leaky or shorted smaller capacitors, faulty
    semiconductors, etc..... also do some tests on the APO stage and check for
    shorted, open or faulty components there.... check for DC on the speaker
    rails before the protection relay. These are all things that can cause
    the "no sound" symptom..... also lots of other things too.
    --
    Best Regards,
    Daniel Sofie
    Electronics Supply & Repair
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


    "Bruno Willi" <bruno*nospamplease*@brunowilli.de> wrote in message
    news:...
    > Hi,
    >
    > my JVC EX-TD55R (a compact stereo system) works fine, just without any
    > sound coming out...
    >
    > There are two relays on the amplifier-pcb. The always 'clicked' when
    > the thing was switched on - no they keep silent. There are some big
    > capacitors (2x 2200µF, 2x 3300µF) - could they make the problem?
    >
    > Maybe someone can send me schematic of this compact system, it would
    > help me a lot.
    >
    > Bruno
     
    Sofie, Aug 1, 2003
    #2
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  3. Bruno Willi

    Wdyorchid Guest

    You might not need a schematic. Just right under the relay are some point you
    want to tap in on them. With a speaker wire to ground and the other to sound
    part of the relay, (not the 6-12 volt or -6-12volt pin) you should hear a
    sound. If not then then it needs to be brought in for repairs. On these make
    I've seen or experince a blown amp a lot.

    >Hi,
    >
    >my JVC EX-TD55R (a compact stereo system) works fine, just without any
    >sound coming out...
    >
    >There are two relays on the amplifier-pcb. The always 'clicked' when
    >the thing was switched on - no they keep silent. There are some big
    >capacitors (2x 2200µF, 2x 3300µF) - could they make the problem?
    >
    >Maybe someone can send me schematic of this compact system, it would
    >help me a lot.
    >
    >Bruno
    >
     
    Wdyorchid, Aug 8, 2003
    #3
  4. Bruno Willi

    Wdyorchid Guest

    The 'click' when switching on is the PROTECTION circuity.
    I am reposting this post correctly below in its intirety due to its valuable
    content. I hope the original poster does not mind for the sake of expanding
    knowledge for humanity:

    Begin:
    I am glad that you CORRECTLY corrected yourself.
    There seems to be a common mis-conception about the PROTECTION circuity in
    audio amplifiers and stereo receivers...... especially among the non-tech
    types.... but even some "techs" may get it twisted a little.
    Here is my treatise on this matter:

    My many years of repair experience with all kinds of audio equipment
    suggests that the "protection" circuity actually protects the speaker NOT
    the amplifier, in most designs.

    When the protection circuitry in the amp senses DC on the speaker
    rails due to an audio stage component failure, the protection relay
    will drop out thus disconnecting and PROTECTING the speakers from the
    very damaging DC... usually full power supply B+ voltage and current
    which can fry the voice coils in most speakers just about instantly.

    Failures in the amplifier circuitry can be easily caused by shorted
    speaker wires, running too many speakers, too loud of a volume driving
    the amp into severe distortion, other component and circuity failures
    due to heat, stressed components, bad solder connections, old age and
    "just because" it was time for a part to fail.

    In most designs, an amp will "try" to drive all of it's power into a
    short or overload (too many speakers) and will quickly cause component
    failures that can NOT be reset.... the protection circuity will sense
    DC on the speaker rails which indicates component and circuitry
    failures that MUST BE REPAIRED ..... in most designs it will NOT
    sense shorted speaker wires and will not PROTECT the amplifier..... the
    purpose is to PROTECT your speakers. Usually when an amplifier displays a
    "protect" message or the protection relay does not click or energize.....
    IT IS TOO LATE...... repairs and replacement parts are needed......
    removing the shorted speaker wires or disconnecting the "too many" speakers
    will not usually fix the problem.

    Best Regards,
    Daniel Sofie
    Electronics Supply & Repair
    End:

    For complete thread see "Anyone know about repair of A/V receivers?" in this
    newsgroup.
     
    Wdyorchid, Aug 9, 2003
    #4
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