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Panasonic SA-200HE receiver not turning on

Discussion in 'Troubleshooting and Repair' started by bookel, Mar 8, 2014.

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  1. bookel

    bookel

    1
    0
    Mar 8, 2014
    When plugged in I hit the power switch and I hear a click. No lights come on and no noise from the outputs.I've pulled every fuse I could find inside and all test ok per my multimeter. I have a schematic for the beast. Unfortunately I am inexperienced when it comes to reading them or electronics repair. I wouldn't even be attempting this but I can't find a repair shop that will look at it. I live far away from the big city. I hate to toss it since it is not a cheap receiver. Just dated but that's okay with me. Anyone want to point me on where to start? I like a challenge.
     
  2. kpatz

    kpatz

    247
    52
    Feb 24, 2014
    Start at the power supply. See if it's putting out the correct voltages. Having a schematic is an excellent first step, sometimes they can be hard to come by for consumer electronics. :)
     
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,267
    Nov 28, 2011
    Hi bookel and welcome to the Electronics Point forums :)

    Yeah, sure! That sounds like a worthwhile repair. And you've given all the important information in your initial question, and used a good thread title. This gets you high marks in my opinion. And you have a multimeter. Good!

    I downloaded the service manual from http://elektrotanya.com/panasonic_sa-he200_sch.rar/download.html. It consists of 22 separate PDFs.

    Search the block diagrams for "AC INLET" to find the power supply section. T701 is the main power transformer; it is energised when relay RL751 is activated.

    The standby circuitry is powered from T751, the "SUB TRANSFORMER". I guess since you hear a click when you press the POWER button, the standby circuitry must be OK.

    So you could start by checking the AC voltages coming out of T701. It has two small secondary windings (one of which goes to the fluorescent display) and one main winding with a centre tap, and four connections which connect to two bridge rectifiers made from discrete diodes.

    Search the schematic pages for T701 and you'll find the "SUB-TRANSFORMER CIRCUIT" section. The secondaries are on the left side of the transformer, and most of them go out on W701. The AC mains input voltage passes through RL751, then enters on CN751. Pin 1 connects to a pin on transformer T701 which goes through a fuse, then to the top end of the primary winding.

    This fuse is a thermal fuse. It goes open circuit if the transformer overheats. They can also fail randomly. If there's no AC voltage on any of the secondaries, but there is AC mains voltage on CN751 after you've pressed the POWER button (be SUPER CAREFUL when you measure this), then it's very likely the fuse has gone.

    Some thermal fuses can be removed and replaced; some cannot. If you can't find it, you might as well start unwrapping the tape to see whether you can get to it.

    You can bypass it temporarily, but NOT permanently, unless you want to void your fire insurance!

    It's possible that the transformer overheated because of some other problem downstream.

    If you DO have AC coming out of the transformer, you'll have to follow the voltages through the bridge rectifiers and on into the circuitry. We'll cross that bridge if we come to it.

    Also can you please put your location in your profile. This can be useful - we can tell which supplier to look at, if we need to specify a replacement part.

    Good luck! And be VERY VERY CAREFUL when measuring AC mains voltages. Connect the meter to the measurement points using alligator clips while the unit is unplugged, then plug it in, take the measurements, and unplug it again before you disconnect the clips.
     
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