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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: Resetting the line adjust on a Hickok with Plate Current Flowing posted by Steve O on September 4, 2003 at 21:26:01:
I tried testing a 6L6 on a TV10, and it behaved much as your TV7 did--the value went up about 10% with the reset. The line adjust circuit is different on these military testers from civilian Hickoks--they have separate instrument rectifiers that drive the meter during the line adjust test. The civilian testers take rectified DC from one of the tester's tubes to drive the meter during the line adjust test.Still, the instructions for the TV10 are pretty clear about setting the line when you turn on the tester and again when you put the tube in to test it. The next step is to press the appropriate test button. There is nothing about resetting the line with the Gm test button depressed at the same time. Even though this CAN be done, the roll chart data is not based upon the tester being operated that way--and if it were--the instuctions for the TV7 and TV10 would have called out the step you described. So--if you don't operate the tester as outlined in the manual, the reject points in the manual would no longer be valid. These reject points would have to be adjusted upward based upon the plate current of the tube under test. There are two more factors to consider. First--it may be that resetting the line with the Gm button depressed COULD damage the tester with certain types of tubes--or with certain types of tube shorts--this I don't know. Second--on testers like the 539 (where the AC line is reset with plate current flowing), the bias must be reset also--something that would require an additional meter.
While I must agree that your reset method does seem to bring the voltages closer to what WE think they should be--this is clearly NOT the way the military intended the testers to be used. We don't know all the reasons why the procedure was written as it was, and my advice is still to operate these testers per the manual. The people that designed all this stuff were pretty clever, and trying to "second guess" their operating procedures is probably not a prudent course to follow.
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Follow Ups
- Re: Resetting the line adjust on a Hickok with Plate Current Flowing - Chris Haedt 04:22:05 09/05/03 (0)
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