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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sun 22, 2003 6:03 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1265
Location: Grand Blanc, MI USA
No one is trying to withold information here. I am trying to be as helpful as I can. In the case of the Heathkit unit you mentioned, the schematic will tell you the voltages that should be present. If these voltages are proper, and the resistors in the unit are all within tolerance, and the meter is of the proper full scale sensitivity--then the tester is probably working as it should. <P>I don't think there are any calibration pots on those testers to fool with. When there are adjustment pots for the meter sensitivity, things get more complicated and judgement and standard tubes are what I must rely upon. If I had the calibration information for all this old stuff from the manufacturers--I would use that. Since such information is usually not available, I rely upon standard tubes, careful records, and experience. So that is the technique--it's as scientific as I can make a rather imprecise subject. <P>One thing to remember too--is that even if we discovered the calibration methods used by folks like Jackson and Precision--the methods and procedures used would likely be very different. For example, some manufacturers call for calibrating the line adjust to the primary on the power transformer, some to a high voltage secondary winding, and some to a low voltage filament winding, and some with a specific load applied to a filament winding. There was no one method used by everyone. <BR><P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sun 22, 2003 9:47 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5191
Location: Rochester NY USA
I guess tube testers are / were a bit of a black art - the tubes don't have a spec for emission, in most cases, or for transconductance at more than a few operating points (none of which are likely to be used in a tester, maybe AVO...)<P>And the tube tester manufacturers didn't want their calibration methods known - it would make things too easy for their competitors. <P>The best bet would be to look up the assembly manuals for some of the "kit" testers, since they HAD to provide calibration instructions. The Knight 600 manual on BAMA, for instance, has a cal procedure using a 6V6. <P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Mon 23, 2003 4:18 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2846
Location: Warwick,RI
[QUOTE]Originally posted by Chris H:<BR>[B]No one is trying to withold information here. <P>Chris....I didn't think you were holding back.I was commenting on Alan's statement that *could* be taken to mean that I was asking for something that someone else had paid a price in sweat and time to obtain.<BR>Of course that **is** exactly what I *was* asking for,but Forum members share such hard earned data here,all the time;every day as a matter of fact.That would not be setting a precedent on my part.<BR>However, there *are* some tube tester repair people who certainly *do** hide their knowledge;this I know because they have outright refused all requests for help and given reasons very similar to what Alan had to say about information learned at a personal price over a period of time.One guy saidto me in an e-mail:"I am not about to shoot myself in the foot to help you"<BR>Thanks,<BR>Malcolm<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Mon 23, 2003 4:45 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2846
Location: Warwick,RI
<P><BR>One thing to remember too--is that even if we discovered the calibration methods used by folks like Jackson and Precision--the methods and procedures used would likely be very different. For example, some manufacturers call for calibrating the line adjust to the primary on the power transformer, some to a high voltage secondary winding, and some to a low voltage filament winding, and some with a specific load applied to a filament winding. There was no one method used by everyone. <P><BR>[/B][/QUOTE]<BR>Ok,but it seems to me that the various methods outlined above all have the same *end result*;but different manufacturers chose to implement the *exact procedure* a bit differently.Right?<BR>So,if we know **why** we are being told to carry out a particular procedure we should be able to apply the **principles** of that procedure to other,similar equipment by a different manufacturer.<BR>In my opinion,singling out the *exceptions* and emphasizing the *differences* in approaches to the same problem as specified by the manufacturer is not the *gist* of the problem,but an **aside**,that must ,of course,be understood *but* only within the context of the bigger,overall picture.<BR>Somebody needs to write up a "General Guide To Tube Tester Calibration for Emission Type Testers."<BR>The procedures that are *known* for certain testers would be given and then the reader would be told how to **interpolate** <BR>"as best as the author has been able to determine"information for unknown testers.<BR>Of course,there would be a disclaimer by the author that he is not responsible for errors,because he cannot know every tube tester or every modification that might have been made to every tester.<BR>There are people here who are qualified to write such a booklet and they could sell it on the internet.<BR>Thanks,<BR>Malcolm<BR><P>------------------<BR>


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