NAD 4080 ... Lights on, nobody home

Discussion in 'Tuners' started by jeffn, Nov 4, 2017.

  1. jeffn

    jeffn Mid-Fi Crisis

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    This nice tuner worked perfectly. Then one day went silent. Meters unmoving. Then another day started up again.
    Now it's silent.
    Lights on, nobody home.

    Any knowledge here on typical issues on these units? I think they're uncommon so I'm expecting too much hands on experience. Thanks in advance.
     

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  2. I LIKE MUSIC

    I LIKE MUSIC Super Member

    Common places to start, switches, power supply and connections, then go from there.

    Are both AM and FM not working?
     
  3. jeffn

    jeffn Mid-Fi Crisis

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    Yes both AM and FM not working.
    I tend to think it's not a switch. The first time it went dead it recovered by itself just by leaving it turned on for a couple of days running then it suddenly worked again.
    The thing lights up so the power supply must be good.
     
  4. I LIKE MUSIC

    I LIKE MUSIC Super Member

    That is not necessarily correct.

    To be clear, it is not uncommon for there to be separate internal power supplies for the lamps and the other internal electronics. Just because the lamps come on does not mean that the tuner section or other sections of the tuner are receiving the correct voltages.

    In terms of trouble shooting, checking for the correct power supply voltages not only means checking to see in the power supply is producing the correct voltages (working) but that those voltages are making it to the correct part of the tuner.

    It may not be a switch issue, but just because it worked then did not work does not in and of its self rule out a switch issue.

    While there are other possible causes for the issue, the only way you will know is to do some basic trouble shooting. Given the symptoms, starting with making sure the correct operating voltages are making it to the tuner section is a very good idea. This is basic trouble shooting 101.

    If the correct voltages are in the correct places then you move on with the trouble shooting process.

    Some additional information. Note the different connections, circled in red and blue for the lamps and the rest of the power supply. The lamps can work without the correct voltages for the rest of the tuner.

    I took a quick look and did not see a schematic for the 4080, this is from the 4020, but is likely to be similar, at least with the dial lamp and operating power supplies being separate.

    upload_2017-11-4_18-40-22.png

    Again, there may be other issues, but one needs verify correct power supply operation, including voltages making it to the correct place (possible bad connections, solder or otherwise), then move on the other possible causes.
     
  5. jeffn

    jeffn Mid-Fi Crisis

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    Wow
    Wow man, thanks for the detailed response. That gives me a great flight path to head off on. I'll let you know how I get on.
     
  6. NAD80

    NAD80 Super Member

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    Last edited: Nov 5, 2017
  7. Dandy

    Dandy Super Member

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    I worked on the NAD 7020 a while back. One of the stereo FM channels was out and it turned out to be one bad capacitor. I then replaced all the other caps, but this was the only one that was bad.

    I agree that checking the voltages is your best next step. It could just be a dry solder connection somewhere. If systematic troubleshooting is not possible, clean all connections and reflow all the solder joints.
     
  8. gadget73

    gadget73 junk junkie Subscriber

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    I'd also give a +1 on caps and solder connections. NAD stuff was decently engineered but their construction wasn't the most amazing. I've only had my hands in two broken NAD items, one had bad solder, the other was bad caps. I found the solder connection by tapping around until it responded, and moving closer to the area with lighter and lighter taps until I found the specific broken joint. Much of the rest of the board had crappy looking solder but one joint had completely broken loose and it would make contact at random.
     

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