Nad 705 repair

Discussion in 'Solid State' started by Eastham, Jan 23, 2018.

  1. Alain L

    Alain L New Member

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    I will do that and see how it goes.

    Thanks for your help.

    Alain
     

     

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  2. Alain L

    Alain L New Member

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    Chatted with Mouser or Digikey and they dont have any matched pair's... Is matched pair's a must?
     
  3. Eastham

    Eastham More Class-A than ever!

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    So long as you get them from the same batch it should be fine not to have matched.
     
  4. Eastham

    Eastham More Class-A than ever!

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    Nad, we did it! It was IC403 all along! Tuner is working and pulling in stations like a trooper!

     
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  5. Eastham

    Eastham More Class-A than ever!

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    Adjusted L402 for 3.05v and now I get full signal on 96.7which is the closes station to me.
     
  6. tanker 200

    tanker 200 Well-Known Member

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    I pulled my 705 out of storage last week and have it connected to a pair of Dynaco A-35's, It sounds very nice. I saved it from the scrap pile a while ago and other than replacing the bulbs for the display it worked great. It has a great sound

    [​IMG]
     
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  7. Eastham

    Eastham More Class-A than ever!

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    They're great little sleepers.
     
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  8. NAD80

    NAD80 Super Member

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    Great news!!!!!. Glad you have it working. Enjoy the MUSIC!!! Now you learned some methods of troubleshooting along the way.
     
  9. Eastham

    Eastham More Class-A than ever!

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    Yup, I also learned a bit about tuners as well, I can't thank you enough for the help.
     
  10. NAD80

    NAD80 Super Member

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    Your welcome. If you have any more questions just ask.
     
  11. Eastham

    Eastham More Class-A than ever!

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    Will do!

    Decided to clean up the previous tech's messy repaste job.

    Before:
    DSC_0971.JPG

    After:
    DSC_0975.JPG

    I used silicone pads and a little bit of arctic cooling MX-4 thermal paste smeered on the pads.
     

     

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  12. NAD80

    NAD80 Super Member

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    Looks much better. Hopefully the thermal paste is non-conductive.
     
  13. Eastham

    Eastham More Class-A than ever!

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    Nope, Arctic cooling's website states the paste is non-conductive, I fired off an email to them and they told me it would be fine to use in this application and will probably perform much better than the original silicone base stuff. Currently have a thermocouple monitoring the temp of one of the outputs, all looks fine so far. Got the Idle current and DC offset all dialed.

    Edit:
    Outputs are currently at 38°c and the heatsink is measuring 37°c so I'd say the pad's and paste are pretty efficient.
     
  14. NAD80

    NAD80 Super Member

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    What is the TC saying the temp is? Glad that it's non-conductive. If it was it could really mess things up.
     
  15. Eastham

    Eastham More Class-A than ever!

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    Edited my post with the temp reading so far. It's been running for about 1 hour now.
     
  16. NAD80

    NAD80 Super Member

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    Nice temp reading, given that Nad doesn't have the largest heatsinks. What are you using to read the TC?
     

     

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  17. Eastham

    Eastham More Class-A than ever!

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    My multimeter, an Extech EX330, pretty solid bit of kit not anything like a Fluke but it's very accurate and built pretty well.
     
  18. NAD80

    NAD80 Super Member

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    Been using a Fluke 12 for years. At work have a Agilent 1242a. Keeps getting borrowed by QA, DC Test guys. I primarily test the AC gear.
     
  19. Eastham

    Eastham More Class-A than ever!

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    Fluke's are the best of the best and make my meter look like a toy, since I only do this sorta stuff as a hobby I can't really justify Fluke prices. The most expensive piece of equipment I own is my oscilloscope a basic, analogue, 20MHz job but it does what I need it to do and I have my MM for testing frquencies.
     
  20. NAD80

    NAD80 Super Member

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    The Fluke was gotten from work years ago. Have 2 Tek 475 scopes to bring up to working status. But for the price I got them for couldn't argue. Saw a single 475 on a cart for 10X what I paid for both. Just have to clean them up. Reseat the connectors, transistors, clean the switches. Then I ought to be good. Got to build the DBT now.
     

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