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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: RE: Why do my NOS power tubes take so much to bias compared w/ new production? posted by blazter on April 29, 2007 at 15:16:19:
as tubes age (and decline in output) they require less negative bias (e.g. more closer to zero) to get to a certain current level. My guess is these are not as NOS as you might think, or at the very least are not biasing up within the spec range. (due to either being out of spec and/or low output, or both). The meter is showing the current draw on them, most likely. Since you can't get the current to the expected range, the bias is off. Changing the resistors may help but it will change the range for more normal tubes, and may also cover up the fact that these tubes may be past their useful life spec, despite what the tester might say (since they rarely measure at real-world operation currents)-Ed
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Follow Ups
- Re: RE: Why do my NOS power tubes take so much to bias compared w/ new production? - Ed Sawyer 18:00:20 04/30/07 (1)
- They certainly LOOK NOS? - blazter 02:48:21 05/01/07 (0)
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