Volume 1 bought the farm

Discussion in 'The Workbench' started by Kunnz, Dec 11, 2009.

  1. Kunnz

    Kunnz Active Member

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    [FONT="Tahoma" ]On my 1969/70 superlead volume 1 has died. Can anyone supply me with a vintage 100k 1W HV carbon comp resistor. The one that ties the volume 1 anode of V1 to the HT?

    Kunnz [/FONT]
     
  2. MajorNut1967

    MajorNut1967 New Member

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  3. Iron Mang

    Iron Mang New Member

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    I think my brother is trying to find out the situation of how the input or channel blew or died? If the plate load resistor was burnt then it was pulling too much current through it. And most likely the tube is toast also or is the culprit.
     
  4. Kunnz

    Kunnz Active Member

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    The channel was working ok after I replaced the bridge-rectifier doides but it stoped working. Yes its a 100K ohm resistor thats for the plate of volume 1 on a 1969/1970 superlead. I de-soldered it out and it's completly open CKT.

    I'm maybe thinking that the HT isnt providing enough voltage for the amp and the components are drawing too much current as I'm having some mains issues.
    Please check the drawing I have circled it.

    Yip I'll change that valve too just in case.

    BTW it would be good to know what kind of voltages I'm supposed to be measuring at various pionts on th HT, I could lower the primaray mains tap to compensate. If you know what the voltages should be roughly then please let me know.
     

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  5. PaoloJM

    PaoloJM Well-Known Member

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    I'd be expecting to see somewhere in the region of 300-350Vdc on the HT side of that resistor. I'd be expecting somewhere between 460 - 530Vdc on the main B+ at the filter caps.
    A shorting preamp valve could easily have caused this and that's what I'd suspect first.
    Under voltage won't cause the amp to draw more current. In fact I'd expect it to draw less current and the valve heaters would be underpowered. Prolonged under voltage is not good and it does damage the heaters.

    What mains issues are you having? What voltages are you reading?
    Dropping mains voltage to compensate for a problem within the amp would certainly not be recommended.
     

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