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JVC DR MV1B , DVD/VCR recorder

Discussion in 'Electronic Repair' started by N Cook, Mar 21, 2007.

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  1. N Cook

    N Cook Guest

    Not my usual area but willing to at least look at it despite inglorious
    reputation googling about.
    Owner was prepared to live with having to press on/off ten times from cold
    before it would settle into on/standby but now there is a sound problem.
    After 2 days powered up all audio functions gradually fail to white noise,
    ie play anything , record anything VCR or DVD or off-air.
    I've located 2 SIL, LA.... (closely surrounded in tiny lytics so cannot
    read) in area of board marked Audio In/Out , any suggestions. ?
    I get the impression it was on left and right so trace power line back to ps
    and selectively heat to induce problem.?
     
  2. b

    b Guest

    You've probably done it I imagine, but change all the capacitors in
    the power supply secondary- these units tend to have abysmal
    ventilation and hence run hot. This gives rise to all kinds of weird
    problems such as the on-off trouble you mentioned. from there, after
    elimination you can delve into the trickier area of the audio circuit.
    -B.
     
  3. N Cook

    N Cook Guest

    Its a dual tuner jobby so worth cobbling something together
    I've now read the numbers on this JVC DR MV1 audio SILs as LA7151 and
    downloaded the pdf, they are dual amps so maybe just a problem with one
    pack, but I'll trace back to the ps anyway.
    There is certainly browning of the pcb around the ps primary side driver?
    STR G6653? and browning to a lesser extent on the heatsink/pcb mounting
    areas, despite a reasonable size heatsink. The owner actually suggested
    putting in another or bigger fan. I will try and find what a Sharp PQ5EV3 is
    also in the ps
     
  4. N Cook

    N Cook Guest

    10.1V supply to the audio amps using an E-line 300mA pass tranny and a 10V
    smoother in the ps. Will uprate those and choke back the easy air supply on
    on the wrong side of the ps to force a greater fraction over the SMPS driver
    and add heatsinks to the 2 unsinked regulator devices. The fan seems
    powerful enough despite its small size, just the internal air run seems
    misdirected as though the ps was the wrong way round, the primary side is at
    a blocked off dead end almost and gaping holes into the rest of the chassis
    at the other end.
     
  5. N Cook

    N Cook Guest

    I RTFM and this m/c blinks for 50 seconds from initial plugging in by
    design.

    Made the changes, will have to see in 2 days time whether repaired.
     
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