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 Post subject: Updated Hickok 539 Calibration document
PostPosted: Dec Fri 16, 2011 6:22 pm 
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Joined: Jun Fri 23, 2006 4:15 pm
Posts: 34
Location: SE England
Hi,

With Daniel Schoo's approval, I've corrected, reformatted and updated his classic document on calibrating Hickok 539B/C tube testers - I have also included data on values need for 230VAC operation.

http://www.desmith.net/NMdS/Electronics ... ation.html

If you find any errors, please let me know.

Thanks


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Dec Mon 19, 2011 1:18 am 
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Nice job. I have another 539C to go thru over the winter. I will use your update, even though I have previously had no issues with the original document(s).


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Dec Wed 21, 2011 7:46 am 
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Joined: Aug Wed 31, 2011 11:23 pm
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Location: Tucson, AZ
Nice review and integration of the information. A few notes on this testing procedure, more FYI for people using this procedure.
Not sure on the statement "Remove the tester from the case and set it up on spacers so that the front panel is facing up in the normal operating position" as the front panel is level, not facing up.

Under the leakage Section, it is important to first adjust the bias so that it reads 40V at maximum bias setting, as this effects the impedance readings. I could not get the impedance to read correctly until this was corrected, the impedance range is driven from the bias voltage.

Under "6 LEAKAGE RESISTANCE METER TEST", one can use a slightly different procedure in accordance with the Hickok 539 manual for checking impedance.

In order for the leakage test to read accurately, the bias meter must be calibrated first so that it reads 40V at its maximum value on the 0-50V range (see Section 10). Connect two leads to the Grid (black pin jack) and Plate (red pin jack). Rotate the SHORTS switch to position B. Short the two leads and the Leakage scale should read 0 ohms, if needed adjust the bias volts (0-50 range) until the meter is zeroed. Connect a 1M, 1/2W, 5% resistor between the two leads and rotate the SHORTS switch clockwise to position B. The main meter should be reading approximately 1M ohms on the resistance scale. Rotate the SHORTS switch back to the TUBE TEST position and disconnect the 1M resistor/leads.

Daniel Schoo's article in AudioXpress in 2007 "Calibration of the Hickok 539C Tester" adds to this procedure. It would be nice to reference or provide a hyperlink to this article in the calibration document, as it adds significantly to the process.

"http://www.circuitcellar.com/AAI/media/schoo2798.pdf" may need to copy and paste in browser to pull up the article.

An alternative for the 83 tube in the Hickok testers is to build a solid state replacement using two standard diodes 1-3A/600-1000V followed by two 5.6V 5W zener diodes (back to back with each diode) and two 10 ohm 2 watt resistors see diagram. This gives 150V (+/-0.5) on the plate when taken with a 1000 ohms per volt meter. Without the Zeners I was seeing 156-157V on the plate, doesn't have a significant effect on GM but does effect plate current. There are slight variations on voltage drop between different standard diodes, usually the higher the voltage/current, the higher the Vf voltage drop. I use 3 amp versions. Since the Hickok testers need to be balanced for plate to plate of the rectifier (or diode to diode) differences, try to match the diodes/zeners within 5% of the Vf. This arrangement provided similar operating voltages/tube test results to the 83 tube at various operating points that I tested. An alternate in all other applications is to use two HV rectifiers such as HV05-08 diodes which have a 6-8V forward voltage drop per diode (NO zeners are required, they would need to be much larger) and the two 10 ohm 2 watt resistors. The HV rectifiers do not work well as a SS 83 replacement in Hickok testers (although they will give 150V on the plate of the Hickok 539) because the Vf can vary up to 0.5V between rectifiers and they are difficult to get a matched pair at different operating currents. This is not an issue when the voltage is filtered.

Another helpful article/calibration tool is Joel Hatch’s “Transconductance Tube tester Standard” article in the February ’05 issue of AudioXpress. It is very simple to make this standard and sidesteps many of the issues around the usual "Hickok 6L6 standard tube" and it does not change between testers or with time. When building the Transconductance Tube Tester Test Standard, you can also add a 3 way switch to short R1 of the voltage divider to give a transconductance of reading of 3000, and either parallel R3/R4 (284 ohm) resistor with a 220 ohm resistor or switch R3/R4 to a 124 ohm resistor(s) for to get a GM of 6,000 with R1 shorted. So you get a solid state standard that gives a GM of 1,500, 3,000 and 6,000. It can be used to verify plate draw which is 11.1 ma with R3/R4 of 284ohm or 22.1 ma (+/-0.1) for R3/R4 of 124 ohm. I recommend keeping the bias at 0 volts when using Joel's "Transconductance Tube tester Standard”, as the IXYS 10M45S can overload with too high a bias setting (between 0-2.5V there is no change in the GM reading, and it is not affected by different plate voltages 100-250V). I also recommend using an external 10 ohm x 50W load resistor for the heater load. The accuracy of the standard was within 3% between validation testing and also between several calibrated Hickok tube testers. It did not work in my AVO testers. Although I have/use several other "calibration tubes" , they drift over time and need to be rechecked/validated periodically.


Attachments:
SS 83 with Zeners.jpg
SS 83 with Zeners.jpg [ 60.3 KiB | Viewed 2722 times ]
SS 83 with NO Zeners.jpg
SS 83 with NO Zeners.jpg [ 61.59 KiB | Viewed 2722 times ]
HV05 Rectifiers Specs.jpg
HV05 Rectifiers Specs.jpg [ 94.82 KiB | Viewed 2722 times ]
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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Dec Wed 21, 2011 3:32 pm 
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mksj wrote:

Daniel Schoo's article in AudioXpress in 2007 "Calibration of the Hickok 539C Tester" adds to this procedure. It would be nice to reference or provide a hyperlink to this article in the calibration document, as it adds significantly to the process.




Yes. That was something I was hoping would be incorporated into the document.


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Dec Thu 22, 2011 7:29 pm 
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Joined: Jun Fri 23, 2006 4:15 pm
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Location: SE England
Thanks for the feedback - I was aware of the AudioXpress article and I appreciate the comments made - over the "holiday" (some chance!) period I'll try to integrate your comments into the main document.

Cheers


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Dec Fri 23, 2011 1:28 pm 
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Your effort is appreciated. Adding the above would make it the only document one would need.


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Dec Fri 23, 2011 3:32 pm 
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Location: Latham NY
This is a great post and thanks to Nick , MKSJ and everyone who contributed. Daniel sure has made it easier to understand and calibrate Hickok testers by his articles on the subject. I am interested in the 6L6 calibration tube sub mentioned (Joel Hatch’s “Transconductance Tube tester Standard” article in the February ’05 issue of Audio Express). Is this article available online anywhere?


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Dec Fri 23, 2011 10:09 pm 
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Joined: Aug Wed 31, 2011 11:23 pm
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Location: Tucson, AZ
Not sure how to access back copies currently since AudioXpress was acquired by the Elektor Group, I do see back issues for sale on occasion. I use to subscribe so had the paper copy. Attached is an adaptation of the circuit diagram, I wanted to test a wider range of GM/MA values as shown. Fairly simple to make and only needs a small heat sink if not run for long periods, parts from Mouser Electronics. I mounted mine in an octal test base and used PVC tubing for a housing. Switch and jacks for external heater load resistor mounted on the top. Should work in most tube testers within the parameters noted. This calibration standard did not work in my AVO tube testers, probably because they use AC or 1/2 wave unfiltered DC on the plate. The 539B is shown with the calibrator at GM=1500 (0-3000 scale), but I suggest using the 0-6000 setting as the signal voltage is lower (0.5V). The readings are the same on either setting of the Function Switch. Let me know if you have any questions.

When calibrating the 539B/C, there are some helpful additions that I feel are important to consider. Once you have checked that all internal components meet specifications, consider adding a multiturn pot for R52 so the grid signal can be adjusted if your signal level is off. I added a switch to disconnect the grid signal (mounted by the function switch), which I often use to check that the GM meter reads 0 when testing tubes. This detects an imbalances or offsets in the tester/tube. I also added a Grid bias fuse bulb, as added to later Hickok testers. It has saved my grid pot from going up in smoke several times.
Mark


Attachments:
Transconductance Tube Tester Standard GM 1500, 3000 and 6000.jpg
Transconductance Tube Tester Standard GM 1500, 3000 and 6000.jpg [ 132.89 KiB | Viewed 2644 times ]
Transconductance Tube Tester Standard Hickok 539B GM1500.jpg
Transconductance Tube Tester Standard Hickok 539B GM1500.jpg [ 137.93 KiB | Viewed 2644 times ]
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