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 Post subject: Proper way to test tubes?
PostPosted: Nov Fri 13, 2015 3:44 am 
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Trying to see if this is the proper way to test tubes or if I've been doing it wrong all along...

When using a tube tester, before a tube is plugged in, I do a line test (which isn't that important I'm assuming) then after all the settings are in place for the tube, I plug the tube in and do a shorts test. 99% of the time there are no shorts, so I go on to test the tube, but before I do, I do another line test with the tube in and it usually is off due to the drain the tube is having on the tester, so I make a line adjustment to center it with the tube in.

This is what I'm questioning... am I supposed to center the line test after the tube in plugged in? This is especially important for power tubes which always seem to be a good away from the line and so I center the line before hitting the rectifier button.

So is that right or am I getting incorrect readings because of this additional line adjustment?


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 Post subject: Re: Proper way to test tubes?
PostPosted: Nov Fri 13, 2015 4:20 am 
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Location: Tucson, AZ
It depends on the tube tester. Most Hickok tube testers, you do the adjustment when you turn it on, and readjust the line test/set with the tube plugged in (i.e. under filament load but not when testing). "This adjustment is made with the control settings properly arranged for the tube being tested and the tube in the test socket".

Some of the laboratory grade testers like the Hickok 539 and 580 series, the voltage adjustments are done with the tube plugged in and with the tube being tested. 539A "Voltage adjustments are made while the tube being tested is delivering its rated load"; 539B/C "Readjust after pressing the P4 Test Button".

The actual readings also vary be tube tester, some state the minimum value, others are the value of a new or bogey tube.


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 Post subject: Re: Proper way to test tubes?
PostPosted: Nov Fri 13, 2015 4:22 am 
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We have to know what tube tester you are using,on some you set the line adjust and leave it, on others you readjust it after inserting the tube. Read your manual it will tell you what method to use.

Dave


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 Post subject: Re: Proper way to test tubes?
PostPosted: Nov Fri 13, 2015 4:37 am 
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Using a TV7 and an I-177. So far it sounds like I'm following the proper process by doing a line adjustment once the tube settings are all set and the tube is plugged in.


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 Post subject: Re: Proper way to test tubes?
PostPosted: Nov Fri 13, 2015 4:01 pm 
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The whole point of the line voltage adjustment is to make sure the tests start from a known place. For the majority of tube testers you are supposed to do this after you've set the switches, plugged in the tube, and given it a chance to warm up. But there are exceptions to this rule, as others have noted, so you have to go by the manual for your particular tester. But it sounds like you've already got the procedure down right for your testers.

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 Post subject: Re: Proper way to test tubes?
PostPosted: Nov Fri 13, 2015 4:22 pm 
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Thanks for validating.


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 Post subject: Re: Proper way to test tubes?
PostPosted: Nov Fri 13, 2015 7:11 pm 
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My Dad had a rather simple approach to testing tubes. He threw them against wall, if they popped, they're good :|

Seriously, be mindful that a tube tester will only test a tube as it would be used in one condition. Most likely if it passes it will work. But high output tubes will be tested at some proportion of there true service load. So it is possible that a tube may well test good but perform poorly in service. For that reason a tube tester is not really adequate to "match" tubes.

GL

Chas

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