Bias Probe - what to get? (2021 edition)

Discussion in 'The Workbench' started by Benighted, Oct 19, 2021.

  1. Benighted

    Benighted Member

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    This is a continuation of an older thread (below).
    https://www.marshallforum.com/threads/bias-probe-what-to-get.61179/

    Most of the probes recommended back then are no longer available (Weber, amp-head). Also, the few good ones remaining are back-ordered (Eurotubes Pro One).

    There are couple Chinese ones on ebay, but they either lack reviews or their reviews are bad.

    So, what would you guys recommend?

    Thanks
     
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  2. don550

    don550 Member

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  3. Chris-in-LA

    Chris-in-LA Well-Known Member

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    For now you could just use the 1ohm resistor and voltmeter method that many of us use. What amp and power tubes are we talking about?

    Take a look at the way Ceriatone adds 1ohm resistors from the power tubes to ports on the back of the amp. You don’t have to be that fancy, just run the resistors to ground. You read the Mv across the resistor and that is pretty close to what the bias is.

    http://www.ceriatone.com/ceriatone/wp-content/uploads/2016/09/JCM800_2204Ceriatone.jpg
     
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  4. RobS

    RobS Well-Known Member

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    agree with Chris above in using 10hm resistors.

    Plus the resistors act as a fuse should something go wrong & are more accurate than the plug in probes
     
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  5. Benighted

    Benighted Member

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    The amp is JVM410h/ 4xEL34
     
  6. pedecamp

    pedecamp Well-Known Member

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    I would think anywhere that sells tubes sells bias probes. Look around and see whats out there.
     
  7. Chris-in-LA

    Chris-in-LA Well-Known Member

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  8. fitz288

    fitz288 Well-Known Yinzer Silver Supporting Member

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    I have the Eurotubes probes, they work great.
    Bias Probes and Multimeters - Eurotubes
    I got a Pro One with the watts option and a basic octal probe that hooks to my meter.
    Can do 2 tubes at a time and dial in the bias settings for a pair.
     
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  9. KraftyBob

    KraftyBob Well-Known Member Gold Supporting Member

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  10. scotheath

    scotheath Active Member

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    Exactly the same set up I'm using, yes those sockets are a tight fit
     
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  11. _Steve

    _Steve Well-Known Member

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    Unfortunately these are backordered too, but good to know about thanks.

    Any others on the market that do both plate voltage and k current?
     
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  12. KraftyBob

    KraftyBob Well-Known Member Gold Supporting Member

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    If you click on "Technical Documentation" about half way down the page there's a link for the Bias Scout Assembly instructions including the parts list. Perhaps you can source the components yourself and built them?
     
  13. fitz288

    fitz288 Well-Known Yinzer Silver Supporting Member

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  14. anitoli

    anitoli Well-Known Member Gold Supporting Member

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    The HJS has the internal bias pins not sure about the 410h.
     
  15. Benighted

    Benighted Member

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    I considered these, but Nobsound probes have very low rating on Amazon. It looks eurotubes probe is the only quality alternative that is readily available.
     
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  16. cozmacozmy

    cozmacozmy Active Member

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