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 Post subject: Tube tester home brew standard question
PostPosted: Jun Wed 18, 2003 12:31 pm 
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Given that it takes X amount of current to cause the needle of an emission tube tester to deflect to the 3/4 scale mark with the emission test circuit set up to measure a particular tube,and assuming we are willing to accept that 3/4 mark as the "normal"reading for that tube,could we then measure the circuit parameters taking place and use those measurements to construct a home brew standard resistance device to be used in calibrating similar emission testers when those testers were also set up to read that same tube type?<BR>Malcolm Leonard<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Wed 18, 2003 2:52 pm 
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You might as well use the tube itself. Some testers DO specify a resistor for calibration, but there is considerable variation among emission tester types. Some testers (Sencore) measure current between cathode and grid, some between cathode and plate, and some apply voltages to all elements. Also--emissions testers are not created equally-- and differ in their transformer's capability to deliver current to the tube under test. To add to this confusion--there is really no agreed upon standard for emission anyway. <P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Wed 18, 2003 6:19 pm 
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Some emission testers use AC and the tube as a rectifier. In this case a pure resistor wouldn't rectify and not give any reading.<BR>Don Black.<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Wed 18, 2003 8:02 pm 
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Location: Stafford, Texas USA
I have been thinking about this for the last month or two. I think that I have a way for a golden device for a tube tester. The one group of tubes that is check on all testers for emission is rectifiers. In Radio News October, 1947 Fred J. Lingel of Triplett Electrical Instrument Co. detail the complete construction for the new emission tester Triplett model 2413 tube tester. This design is what most emission tester used for the next 25 years by, Heath, Knight, Eico, NRI, Conar, Lafayette and others. This group of tube testers uses a combination of lever and rotating switches with the lever switches numbered to correspond to the RMA tube pin numbers. For maximum assurance against plugging tubes in the wrong socket, this tester provides only one socket for each type of tube base. The data looks differ from one tester to the other because of the game that was play with the wiring of lever switches; the basic circuit is the same. A 1 ma meter in series with a resistor on a switch most of the time called (A circuit) that was shunt by a pot called (C load) 200 to 300 ohms, Cathode return resistor of 50/51 ohms, and 30 vac out of the transformer. The golden device is in a socket 4,6,8, like Alan’s 83 replacement but a resistor is added in series from the center tap of the resistors to the cathodes of the 1N4007’s diodes. The value of the added resistor needs to be such that then the tester is set up for a 5y3, 83, etc the meter read 70%. To take one more factor out set the load to 0 before the value of the resistor is set. All resistors need to be 1% or better. Well my ride is here for HamCom in Dallas so if anyone is going I am at table A20 indoor flea market.<P>Jimmie<P>Don I think all tube tester use AC an turn the tube in a rectifier testing emission? <P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Thu 19, 2003 12:31 am 
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I had bookmarked that article years ago but hadn't read it lately; thanks for the reminder. I liked Fred's jab at "trick switching circuits" that made it difficult to understand what the tester is doing (take that, Paul Jackson).<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Thu 19, 2003 3:37 am 
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Jimmie or Alan.....I'd love to read that article.Any chance of getting a xerox copy if that is not putting you guys off schedule or making you go out of your way too much?<BR>Thanks,<BR>Malcolm<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Thu 19, 2003 4:21 am 
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Location: Rochester NY USA
I'd like to read it too. If someone can scan it, I'll put it on my web page for all to read. <A HREF="http://www.Aduiophile.cjb.net" TARGET=_blank>http://www.Aduiophile.cjb.net</A> <P>I'm thinking of building a transconductance tester myself, as described on Steve Bench'e page - link on my site above.<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Thu 19, 2003 7:36 am 
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I'm on my way to HamCom in Dallas I get back to Houston sunday I will send the article to all that would like it.<P>Jimmie <BR><P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Thu 19, 2003 11:26 pm 
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Don is correct--you need a diode in the circuit to rectify the AC supplied by the tester, and supply DC to drive the meter. Sencore specifies a plug in resistor/diode module like this, to calibrate the emissions function on the MU140 and MU150 models. But--the Sencore system measures current between the cathode and the grid only--it ignores all the other tube elements. On this model, the emissions function is just a secondary test. <P>More complex emissions testers (Jackson 648,Eico 666, Precision models) apply AC voltages to all elements so that an open element will affect the meter reading. This is why I suggest a tube might be a better way to go--as then you are working with the entire tester. Plus--I would not suggest calibration based on a high current tube like a 5Y3 or 83. On small emissions testers--the tube may have much more current capacity than the transformer in the tester can supply. In other words-these types of testers tend to see even weak tubes like this as good. Emissions testers tend to show less agreement on rectifier tubes than on other types--for this very reason. It does not seem like this would be so--but that is my experience.<P>So--I guess my opinion is that no one device would work to calibrate the many types of emissions testers that are found. Clearly, the people who made the tubes and the testers themselves did not completely agree on what was a good or bad tube. <P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Fri 20, 2003 2:38 pm 
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Chris,<BR>What about using 6 NOS tubes,all the same tube number,weeding out the highest and lowest reading of the six and averaging out the readings of those tubes that remain *after* the highest and lowest have been *eliminated* from the running?<BR>Let us say I ended up with three tubes (after weeding out highest and lowest) having readings of 70,76 and 74 respectively.<BR>The average would be 73.3.<BR>So,I then plug the tube that read 74 back into the tester(since I need a load of some kind in place at that time it and it is the closest reading tube to my ideal 73.3)) and I now set the internal needle calibration control for just a shade over 73 on the meter scale.<BR>Am I all wrong here,or does this make sense?<BR>Thanks,<BR>Malcolm<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Fri 20, 2003 7:32 pm 
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If I said ALL tube testers use AC I'd be deluges with examples that use DC. I guess most use AC but at least some laboratory type testers use DC. There was the remains of such a tester at the last HRSA auction that I think had 7 regulated DC power supplies. But these are unusual from the typical service testers. I've got enough nits without picking any more <IMG SRC="http://antiqueradios.com/forums/smile.gif"><BR>Don Black.<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Fri 20, 2003 8:20 pm 
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>>What about using 6 NOS tubes,all the same tube number,<P>But different testers check tubes at different currents. Signal diodes for instance (6SQ7 etc) are typically checked at 1mA or thereabouts, but a few testers run them at 10mA. If you had a tube whose total emission was 5mA, it would test fine in most testers, and work well in a radio, but would fail in a few testers. Who is right?<P>It's a can of worms.<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sat 21, 2003 3:52 am 
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So,without the data from the tester manufacturer we can never be sure,then?<BR>Or,as an alternate we could,of course,have somebody who owns the same model tester test a tube for us and copy his result,but only if his tester has been pre-set to factory specs?That seems to be the unfortunate situation here that we are up against.<P>I had heard that Hickok had test "jigs" of some sort.I guess these were resistance standards,actually?<P>I had read somewhere that most properly calibrated emission testers test most "good" tubes at about 70 on the meter scale.<P>I am talking about Heath,Knight,Precision,etc.,not the more costly,complicated "modified emission test" models.<BR>Malcolm<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sat 21, 2003 3:59 am 
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[QUOTE]Originally posted by Don Black:<BR>[B]If I said ALL tube testers use AC I'd be deluges with examples that use DC. I guess most use AC but at least some laboratory type testers use DC. There was the remains of such a tester at the last HRSA auction that I think had 7 regulated DC power supplies. But these are unusual from the typical service testers. I've got enough nits without picking any more <IMG SRC="http://antiqueradios.com/forums/smile.gif"><BR>Don Black.<P>Unfortunately,nit picking can be and often is overdone,but thankfully,the Forum is not as bad in that respect as some other places we all know about.<BR>The more basic emission testers I am somewhat familiar with use rectified AC for line adjust and "pure" AC for other tests as I recall, with the tube being tested at the moment acting as a rectifier whether it actually is one or not.<BR>Malcolm<P><P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sat 21, 2003 2:37 pm 
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Location: Grand Blanc, MI USA
Alan makes good points about the variations in testers, and how they "view" different tubes. This seems to be even more evident in the emissions tester field. While the readings obtained on mutual conductance testers may vary, most properly working machines will agree upon what is a good tube and what is a really bad tube. This is not always the case with emissions testers, nor is it always the case when a mutual conductance tester is being used to test for emission on a rectifier tube.<P>The initial question posed to the Forum was certainly reasonable, but shows how there is generally more to a subject than would first appear. Sadly, we are unable to speak with the people that designed the testers and ask them why they chose the standards they did. But--since the standards varied--it is hard for us now to calibrate different testers with a universal device. <P>As a practical matter--I do think you could select an "average tube" (I suggest a 6V6 or 6K6) and use it to test most emissions testers. But--once you have done that--you must be sure that a weak tube reads weak also. Remember that the ultimate purpose of the machine is to identify weak tubes that would cause trouble in a radio, not to identify "average" tubes. <P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sun 22, 2003 4:41 am 
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<P>As a practical matter--I do think you could select an "average tube" (I suggest a 6V6 or 6K6) and use it to test most emissions testers. But--once you have done that--you must be sure that a weak tube reads weak also. Remember that the ultimate purpose of the machine is to identify weak tubes that would cause trouble in a radio, not to identify "average" tube<BR>Chris,<BR>I know you calibrate tube testers on a routine basis,sell and guarantee them.Would you share, in a specific manner with us what your own approach is to calibration of a low end(Heath,Precision 612,Knight,Eico 625,Paco) tube tester?<BR>Thanks,<BR>Malcolm<P><P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sun 22, 2003 5:17 am 
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I have a data base of hundreds of testers and how they have tested various tubes. Each tester I calibrate needs to properly identify the good/bad/marginal tubes (as well as the particular machine design can be expected to do so). I do the thing with tubes and there is no real way to transfer that easily to others. There is certainly some judgement involved, and it is not an exact science. I wish I could make it more exact--but for the reasons we have discussed--there is no simple approach.<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sun 22, 2003 5:24 am 
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There's a loaded question. A lot of this knowledge is acquired through time-consuming (which means expensive, if it's your means of support) trial and error.<P>Guaranteeing your own work is one thing; making mistake-proof procedures for others to follow, is beyond your control.<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sun 22, 2003 4:03 pm 
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Alan,<BR>I don't recall requesting "mistake proof" information nor did I intend holding any man here responsible if his information was less than perfect.<BR>Such an attitude on the part of any member here toward any other would certainly be a new experience to me.<BR>Information is neither demanded nor expected to be faultness in this Forum that I am aware of.<BR>It is all very much **voluntary**.<BR>However,should anyone feel inclined to with hold hard earned,money making information;then,so be it.<BR>But in that case it is best not to comment at all rather than offer only the negative aspects for consideration by less knowledgeable members,who may be led to feel that a particular technique is simply too much trouble to bother learning.<BR>While I do admit that your electronic knowledge far exceeds my own,I do not believe that calibrating a simple emission tester of the general type mentioned earlier in this thread is a terribly difficult undertaking that requires years of hard earned experience and almost alchemical knowledge.<BR>Why? Because the instruments themselves are incapable of anything approaching pin point accuracy anyway.<BR>A $39.95 Heathkit tube tester is hardly rocket science.<BR>Anyway,I do thank you and everyone else for your time and feedback on this post.<BR>Malcolm<P>------------------<BR>


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 Post subject: Tube tester home brew standard question
PostPosted: Jun Sun 22, 2003 4:55 pm 
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I'd have worded my reply a little differently if I'd known that Chris was answering first. Sorry if it seemed a bit confrontational.<P>------------------<BR>


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