Power Supply on Dumont Model 526 Stereo Console Smokes

Discussion in 'Technical Repair' started by shazam96, Jun 26, 2016.

  1. shazam96

    Thread Starter New Member

    Jun 26, 2016
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    Hello Everyone,
    Just purchased a Dumont model 526 stereo console with a Garrard turntable. And found a Eagles Hotel California album at the same flea market. Excited, but knowing this beast is older than me (and I'm old) ... Brought it home.. rewired the power and plugged it in.. It worked! The FM radio and the turntable... I was so excited... Sounds awesome! However, after a few minutes or less I smelled something burning. So, I unplugged and pulled the back panel off. Plugged back in and identified where the smoke came from. Power supply or amplifier... not sure... There is two components on the side that, I believe look like transformers... That's where the smoke was coming from.... so, I turned it off and ..... found this thread..... I'm sure most people would ask if this power supply/ amplifier is worth fixing and/or replacing.... or just put a new amp and hook up to the speakers.. Thanks!
     
  2. JWHassler

    Member

    Sep 25, 2013
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    Could be the dust burning off... if it hasn't been run in awhile
    Look around for schematics.
     
  3. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Yes, indeed it may just be dust burning off.
    Make sure you are supplying it with the correct power voltage.
    After running it for a little while, switch off and feel the transformers - they may be gently warm but should not be hot.
    Also have a feel of large metal can capacitors (like on the right side of 165457.jpg) they should be cold - even warm would indicate a problem.
    Be careful poking your fingers into it immediately after switching off as there will still be some stored voltage on capacitors.
     
  4. shazam96

    Thread Starter New Member

    Jun 26, 2016
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    Thank you JWHassler and AlbertHall. I plugged the Dumont back up and it continued to smoke. So I pulled the amp out and the transformer for one of the speakers is fried... So, I went to a stereo shop and asked about getting a new amp... He said he needs to know what the impedance is for the speakers ..... Any idea how to find out?
    Cheers!
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Can you measure the DC resistance? What you read will be somewhat lower than the quoted impedance. So a 4 ohm speaker will read around 3 ohms, an 8 ohm speaker around 6 ohms, and a 16 ohm speaker around 13 ohms.
     
  6. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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  7. shazam96

    Thread Starter New Member

    Jun 26, 2016
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    Hey Albert, finally got a meter checked the speakers. It read high 5's ohms.
     
  8. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Fairly safe to say they are 8 ohm speakers then.
     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    The wax filled capacitors need to be replaced and the old carbon resistors will have drifted way higher in value than the color code indicates.
    Getting reliable operation would require an extensive replacement of components.
     
  10. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Check Post #4.
     
  11. shazam96

    Thread Starter New Member

    Jun 26, 2016
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    Thank you Albert!.. now I need to figure out were to get components... the waxed capacitors and resistors.. also when I had it powered up the tunes were very hot
     
  12. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    I checked #4, but the components I named still need to be dealt with.
    If you mean you already mentioned such, I fail to see it.
    My apologies if you did and I missed it two times
     
  13. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Confused... Are you replacing this amp or repairing it?
     
  14. shazam96

    Thread Starter New Member

    Jun 26, 2016
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    Sorry for the confusion. I'm going to attempt a repair... thank you for taking the time, Albert, I appreciate it.
     
  15. shazam96

    Thread Starter New Member

    Jun 26, 2016
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    Hello! I have finally made it home with my Dumont 526. I'm ordering parts for the amplifier now. Just wanted to reach out and ask where I might have any luck in purchasing paper condensers... Here's the specs on the component.
    United Condenser Corp
    UNICON
    MP .033
    WVDC 400
    outside foil
     
  16. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Unless you are desperate to keep it with original parts, use ceramic or plastic film capacitors.
    I don't think anyone makes paper capacitors, so any you get will be old and they slowly absorb moisture from the air and become leaky.
     
  17. tcmtech

    Well-Known Member

    Nov 4, 2013
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    By chance have you had the tubes tested to make sure they are within working specs?

    If you have a bad one on the side with the cooked transformer it could be due to a shorted tube which if so will just cook your replacement transformer.

    As others mentioned, unless your going for originality just replace the old components with modern version that match the values which in the case of you old can type capacitors you can cheat and have the original look but new parts by gutting the old cans and sticking the now physically much smaller modern ones inside.
     
  18. shazam96

    Thread Starter New Member

    Jun 26, 2016
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    Haven't been able to find a tube tester. ... and I'm completely fine with modern vs. originality. .... Right now I'm going for the obvious to me. And since I'm very rookie-est to this work... Thank you for the heads up on the tubes... Obvious, so far, is replace the transformers, paper condensers, and test tubes...
     
  19. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The paper capacitors may well be the cause of the cooked transformer. Where a paper coupling capacitor is connected between an anode and the grid of a 'tube', any leakage raises the grid voltage and anode current. If that 'tube' has only a transformer at its anode the transformer releases the magic smoke.

    BTW I have a valve tester but that difference in terminology tells me that I am at least 3,500 miles away from you!
     
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