Need 7 and 9 megaohm resistors, where to get?

Discussion in 'General Electronics Chat' started by ScottCT, Oct 19, 2015.

  1. ScottCT

    Thread Starter New Member

    Feb 17, 2009
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    For a Heathkit VTVM, need 1% resistors at least 1/2 watt, 7 and 9 megaohms.
    Any idea where to get them, Mouser and Digikey no have.

    TY
    Scott
     
  2. GS3

    Senior Member

    Sep 21, 2007
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    What's wrong with 1 Mohm resistors in series?
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
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  4. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Why do you need at least half watt?
    It would take at least 2,100V to dissipate 1/2W into a 9Mohm resistor.
     
  5. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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  6. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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  7. strantor

    AAC Fanatic!

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    When I googled "Heathkit VTVM" I saw a bunch of VOMs that only measured up to 15VDC.
     
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    They are reference resistors for the vacuum tubes. I think 1/2 watt is recommended to limit heat extremes of "properly" sized resistors and limit heat effects on accuracy.
     
    strantor likes this.
  9. strantor

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    Oct 3, 2010
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    Got it, thanks!
     
  10. ScottCT

    Thread Starter New Member

    Feb 17, 2009
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    The 7 and 9 megaohm are part of the main voltage divider reference. The existing ones have drifted a little high, which throws off
    voltage readings. Ohmcraft might be a possibility if they will sell one off. TY Keepitsimple
     
  11. umphrey

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    Dec 1, 2012
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  12. JohnInTX

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    Jun 26, 2012
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    Here's a search at Mouser that gets pretty close. 9.09M 1/2 Watt, 6.81M .4W, in stock. Monkey around with the filters for other close ones. Lots more 1/8Watts. Maybe parallel a couple. Vishay is a good go-to for things like this.
     
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