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denon 3801

Discussion in 'Electronic Repair' started by JR, Jan 9, 2007.

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  1. JR

    JR Guest

    hello...yall might remember me trying to find problem with 3801 denon
    receiver i bought that wouldnt power on...wont do anything. Mark sent
    me a service manual, i tried to find problem and finally give up. I
    finally sent the receiver to a denon repair shop..they called today,
    said the micro processor was out and would have to be replaced before
    they could further troubleshoot, and could cost as much as 760.00 to
    repair. I told them nevermind and to send it back. Mark said he bet i
    had a cracked circuit board.awhile back when i was trying to find
    problem..any tips on how to locate a cracked board or an easy way to
    check? Would i have to tear receiver all the way down and pull all the
    individual boards to check?

    Thanks
    JR
     
  2. Arfa Daily

    Arfa Daily Guest

    I think I was actually the first to suggest a cracked board when you first
    posted. I would think that the system control micro being faulty, whilst
    possible, is unlikely. I have a friend who has this "rule" that the more
    pins a device has, the less likely it is to be faulty ... Just a joke, but
    actually, not a bad maxim to live your repair life by in practice.

    For sure, you could pull every board out and physically examine it, but
    really, it just wants either fault finding properly, or giving a second
    opinion by a reputable repairer. The lot you already took it to are taking
    the piss suggesting $760 to repair it. That actually says that they either
    can't do it, or don't want to, so are doing the old "price it ridiculously
    high and he'll walk" trick.

    The system control micro area is generally easy to troubleshoot for a fault
    like this. You only need establish that the 5v supply is good and accurate,
    the reset line is at the right level, and the system clock is running. After
    that, you check for activity on the switch matrix lines, in particular,
    those running to the standby switch. Make sure that they do something when
    you push the button, preferably right back at the appopriate pins on the
    micro, but at the switch pins will do at a pinch. After this, if all is
    well, you would need to check the "power on" line coming back out of the
    micro, which should toggle as a result of pressing the standby button. There
    are odd little problems that could throw a spanner in the works of this
    simplified procedure, but for 99% of cases, those are the checks, in that
    order, that will establish whether or not there is a sytem control micro
    problem. However, all this assumes that you have a 'scope to hand, and are
    able to read and follow schematics and layout drawings properly.

    Arfa
     
  3. carneyke

    carneyke Guest

    Arfa,
    Excellent microprocessor troubleshooting advice ! Take Care, Kevin
     
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