Section I:  General Precautions

This unit uses potentially hazardous voltages.  During testing, these voltages are present on exposed terminals.  Do not touch any tube socket or jumper while testing is in progress, especially if any buttons are depressed.

The control box gets rather hot in certain areas after prolonged use.  This is normal.  Turn the unit off when not in use.

The sequence of what gets turned on or off first is not critical.  There is one exception.  Do not turn the control box on if the program is already running and a test has been started.  Exit the test first.

This unit is user programmable.  It is possible to program tests that can destroy a tube.  TubesontheWeb.Com, LLC, assumes no responsibility or liability for the misuse of this product.

Section II:  Initial Setup

After unpacking, set up the unit near the computer system to be used.  The computer should meet the following minimum requirements:


Getting started is easy.  Just connect the supplied cable from your computer's parallel port to the control box.  If using the floppy disk, load the software by running the setup.exe program that comes on the floppy disk supplied with your unit.  To run this program on a DOS computer, insert the disk, then type A:SETUP at the DOS prompt.  On a Windows 95 or newer system, click on Start, then select Run.  In the box that pops up, type A:SETUP and click OK.  The setup program then guides you through loading the software on your system. If using the USB stick, set your computer to boot from the USB port. If your computer does not support booting from USB drives, you can copy the tube tester software from the USB stick to your hard drive.

The software defaults to using parallel port LPT1 on your computer, which is usually addressed at 378 hex.  This is the most common configuration on computers that have only one parallel port.  If the port you connected the control box to is at a different address, you will need to enter this address during the software installation.  Valid addresses are 378, 278, and 3BC.  If you are not sure, just select the default.  This setting can be changed at any time by accessing the System Test Menu.

Be sure to connect the short jumper to the plate current meter jacks.  The unit will not work without it.

Once the software is installed, there is a one time setup procedure that should be performed.  This procedure sets the tester to match your AC line voltage.  To perform this procedure now, do the following:

NOTE: The software automatically selects the proper filament voltage for each tube, based on its current draw.  It is no longer necessary nor desirable to perform the filament standard adjustment for each tube.  If you do want to check it, do it before the tube is inserted.

Section III:  Software Navigation

The software is easy to use and generally self explanatory.  However, a few pointers about keyboard commands are in order:

Section IV:  Menus

The Main Menu has six selections:

(0) - Exit

(1) - Test Tubes

(2) - Add Custom Test

(3) - Calibrate Tester

(4) - Re-index Data Files

(5) - System Test Menu

Many of these selections are discussed in more detail in other sections of this manual.

Section V:  Testing Tubes

This section assumes you have inserted a tube and have called up a test.  Most of the following information can be found in the tube tester's original manual, but is repeated here for convenience.

Tube testing is a three step process for most tubes.  The tester's buttons and meter scales are labeled 1, 2, and 3 to correspond to these tests.  For the purposes of this discussion we will assume a tube is already inserted and the test started at the computer.  Never forget when calling up a tube to make sure you really are on the right tube.  Also note whether or not there are any special instructions.  Then press the "T" key to start the tests.

Step 1: Shorts and Leakage

Just below the meter there is a metal hood which shades 5 neon lamps.  These are the shorts indicators, and are the first thing you should check.  They become active as soon as the test is started at the computer, you don't have to press any buttons on the tester.  If any of these lamps are flickering or glowing, then an inter-element short in the tube is indicated and the tube should be considered bad.  Do not press any buttons and do not continue testing if any of the shorts indicators are glowing.

If you want to perform a more sensitive grid shorts test, open the hinged door on the right side of the tester and press the "Sensitive Grid Shorts" button.  It is a good idea to just get in the habit of performing this test, especially on audio tubes.  It will cause the grid shorts lamp to glow if the tube has even an extremely small leakage path to the control grid.

Now observe the meter.  With no buttons depressed, the meter is indicating the heater to cathode leakage.  We are on step one, so we read the top meter scale, appropriately labeled with a "1".  If the reading is not within the green area on the top meter scale, then the heater to cathode leakage current is excessive.  This completes the shorts and leakage tests.

Step 2: Quality Test

The quality test is performed simply by pressing button "2" and reading meter scale "2".  The meter indicates the tube's "quality".  Anything above half scale is passing, anything below that is failing.  You can consult the computer screen to convert this reading directly to uMhos or mA.  If the test is a transconductance (uMho) test, you can make sure you are getting a very accurate reading by pressing the "Grid Sig. Off" button.  Again this button is under the hinged cover on the right side of the tester.  This should make the meter drop to zero, indicating a perfectly balanced Gm bridge measuring circuit.  If the reading is something other than zero, you can use the Gm Balance controls to null the meter to zero.

As a part of the quality test, you may wish to perform the cathode activity test.  Press the "Cath. Act." button.  This reduces the heater voltage by 10%.  If after 1-1/2 minutes the reading has dropped by more than 10% of the tube's normal reading, then the tube should be rejected.

Sometimes the shorts lamps may flicker or glow during the quality test.  This is normal.  The only time you should pay attention to the shorts indicators is when button "2" is not pressed.

Step 3: Gas Test

The last step is the gas test.  Press button "3" to perform this test, and read meter scale "3".  If the tube is excessively gassy, the meter will deflect above the green area.

The tests are complete unless the lamp next to button "4" is lit.  This indicates a dual section in the tube that can be tested with a single test.  Simply perform all the tests twice, once with button "4" held down, once without.

If there are no other tests programmed for this tube, you are done.  The computer screen will indicate how many tests are involved for this tube (it could be anywhere from 1 to 6 tests) and which test you are currently on.  To end this test and/or go to the next test, release all buttons and press the space bar.  Please do not press the space bar (or ESC) before releasing buttons "2" or "3".

Section VI:  Software Overview

This section will take us step by step through calling up a tube, testing it, creating a custom test, and setting up a curve trace.  Please follow along on your computer.

When the software is launched, the Search Screen is the first screen we see.

Simply type the number of the tube to be tested into the upper field (fields are areas which you can type in and they are always blue) and then press ENTER.  If desired a partial number may be entered.  The lower field, Power Search,  is used to search the database more thoroughly and also lets us use the program as a cross reference (more on this later).

Type in KT66 and press ENTER.  Check out the screen we are presented with.  Whoa!  There is a lot of information there, but don't let that scare you.  In fact, if all we wanted to do is test this tube, we wouldn't be concerned with anything on this screen except to confirm that we have pulled up the right tube and the number of tests involved.  We could simply press the "T" key (for Test) and we are testing.  Now that's fast!  At this point the tester is operating just like we had inserted the KT66 test card.  We complete the testing procedure just like we normally would on any Cardmatic:

1) - Check for shorts by observing the tester's short lamps, and read the meter to check for any heater to cathode leakage
2) - Perform the quality test (press button 2 and read the meter)
3) - Perform the gas test (press button 3 and read the meter)

That's it!  It really is that easy to use.  If we wish, we can convert the meter reading obtained during the quality test directly to uMhos by consulting the color coded meter conversion chart on the right side of the screen.  If the tube has more than one test, we press the space bar to take us to the next test.  Pressing ESC takes us back to the search screen and we are ready to test the next tube.  If all you want to do is test tubes, you are done.  But, if you want to do more, read on.

The rest of the information on the screen is there only if we need it (or are curious).  For example, after studying the test parameters we may decide that for our application a more accurate test could be accomplished if we changed the conditions under which the tube is being tested.  To achieve this, we can easily add a test to the database that uses our parameters.  Lets do that by pressing ESC to return to the search screen, then pressing ESC again to get to the Main Menu (pressing ESC from anywhere always takes us back).

There are several options.  For now, lets just select item 2, "Add Custom Test", so we can input our modified KT66 custom test.

Since we will still be testing a KT66, we should answer this first question "Yes" and tell it to read the data from the KT66 already in the database.  That way things like the type of test, pin out, and filament voltage are already properly set for us.  If this question is answered "No", then we could change things like the type of test (Transconductance or Plate Current) and bias mode (grid or self).  For now answer yes, then KT66 for the tube to read the data from.

In this case we are looking at a Transconductance test using grid bias.  What we decide to change is the plate voltage.  We are going to set it at 180V.  Unfortunately we can't go much higher because we start to run into the limits on the amount of current we can draw from the regulated B+ power supply.  We will also need to increase (make more negative) our negative grid bias to keep the tube's operating point within the proper range for the gm measurement bridge circuit.

We start by giving it a name like KT66Spl (for KT66 Special) and changing the parameters just mentioned.  When we have filled in all the fields and reached the bottom of the screen, the program asks us to confirm our changes.  After pressing the "Y" key, it then stores our test in the database along with all the other tests.  The original KT66 test is still there too, untouched.  Now go back to the search screen, pull up KT66Spl, and lets look at it in more detail.

First we will discuss at the upper section on the screen.  It contains three fields of information that we can edit if we wish:  the type number, an optional alternate number, and a place for remarks.  The type number is simply the number that the tube is known as.  The alternate number is used when a tube is also known by second number.  For example, the 6BQ5 is also known as an EL84.  This alternate number field is included in the search when using the Power Search that we mentioned earlier, which is how the program functions as a handy cross reference.  Next, the remarks field is used anything we might need to know.  For example, a test might be one that measures a tube's ability to achieve complete cut off, and any reading under 50 on the meter indicates a good tube.  In that case the remarks field will say "OK UNDER 50", so pay attention to this field.  We can add to it anything we like, but please do not change anything that is already in this field.  The upper section also shows the total number of tests involved for this tube and which test we are currently on.

The right side of the screen holds the meter conversion chart.  In this case it is a transconductance test so we can convert the meter reading directly to micromhos by consulting this chart.  If this were a current or voltage test, the chart would convert directly to mA or volts for us.  The chart is color coded: good tubes will register in green numbers, marginal in yellow, and failing in red.  It is a sliding chart that adjusts automatically to match the test.  At the bottom of the chart there is a notice that the letter "O" key (stands for Odd/Even) can be pressed at any time to toggle the chart between odd and even numbers.

The left side of the screen shows what tester line is connected to what tube pin.  This is worded as "tester lines" intentionally  because these lines are not always used for what they seem.  The tester circuit is so versatile that it is sometimes handy to use a line for something other than what it is labeled as.  Do not design your circuits using the pin out shown on this screen!

The central area of the screen shows the test parameters.  Some of these fields change depending of the type of test being performed.  In this case most of the parameter fields can be edited, or changed,  because this is our custom KT66 Special test that we added earlier.  These fields cannot be changed in the 3800+ tests that come with the tester.  Of particular interest is the "Adjusted Filament Voltage" field.  This is the voltage actually being chosen from the filament transformer taps, and is based on the amount of filament current being drawn.  It makes up for the voltage drop in the wiring so that the tube receives the proper filament voltage at the pins.  Low filament voltage, especially on low voltage high current tubes, has always been this tester's biggest weakness.  This problem has been completely eradicated since the computer picks the right voltage automatically!

At the bottom of the screen are the commands we can use.  They are all one key commands, so all we need to press is the key indicated in the parentheses.  Let's take a look at each, in order.  The first, (C)urves, is discussed in the next section.  The next command, (D)elete, is pretty much self explanatory, and appears only on custom tests.  None of the tests that originally come in the tester's database can be deleted.

Next, (E)dit, is used to change any fields on the screen that are allowed to be changed and is very simple.  When the "E" key  is pressed, the cursor moves up to the top field.  Make any changes needed using normal editing keys (delete, insert, etc.).  Use ENTER or the down arrow key to skip any fields that do not need changes.  Use the up arrow key to get back to a previous field.  After making changes, either press ENTER repeatedly to get to the bottom of the screen, or press Page Down to skip the remaining fields.  If one or the other isn't done, or ESC is pressed after making changes, then the changes will not be saved.

The (I)nstructions command is needed only if you have not read this document.  Pressing the "I" key in this case will give us only generic instructions that we have already covered.  On the other hand, if there are instructions that are specific for the tube being tested (such as most voltage regulator tubes), then the instructions will automatically pop up in the central area of the screen when you first call up that tube.  For example, pull up 0A2 and look at the test screen.  As you can see, the parameters that are normally presented in the central part of the screen has been replaced with instructions specific for this test.  Also a new command, (D)etails, has appeared that can be used to switch from the instructions to the parameter display that is supposed to be in the central screen area.

The next command, (R)elays, is a screen that shows which switches (relays) are closed for this test, and a graphical representation of the card, if we cared.  This screen is only used for diagnostic functions.

The all important (T)est command is next.  Simply insert the tube into the tester and press the "T" key to start the test.

The rest of the commands are simply (Q)uit, which exits the program completely, and representations of the left and right arrow keys, (<) and (>), which lets us quickly move backward and forward through the tube database in numerical order.  For example, to bring up our KT66Spl test, we could just type KT66.  When the KT66 test screen (the original one) comes up, pressing the right arrow key makes the program go to the next test, which in numerical order would be the KT66Spl test we are looking for.

Section VII:  Curve Tracing

First, we will be going through the process of setting up the curve test parameters for our newly added KT66 Special, but don't get confused here.  The set up procedure we are getting ready to discuss can be tedious, but once completed the process of creating the curve charts themselves is quick and easy (much easier than the initial setup procedure).  Here is a quick overview of the curve trace process, once the parameters have been set up:

Excel macros are provided on the program disk that automates the process of displaying and/or printing the curves.

To look at these steps in detail, we will start with our KT66 Special that we already have pulled up on the screen.  Again, please follow along on your computer, or none of this will make sense.

When we press the "C" key, one of two things will happen.  Normally, a tube will already have had its curve test parameters entered, in which case the program will take us directly to the curve trace test screen.  However, these parameters have not yet been set up for our KT66Spl, so when we press the "C" key we are taken to the curve setup screen.

Hopefully, to save time, there will be other tubes with similar characteristics that already have their curve parameters set.  If so, we can read the default data in from one of them.  Setting up a good curve is usually a process of trial and error.  Fortunately, once a curve is set up for a particular tube it is stored in the database.  Most common audio tubes already have the curve test parameters set up.  But for now we are going to answer "No" to this question and setup a curve from scratch.  This takes us to the first part of the setup process, the tube's pin out.

Remember the program can only guess at the pinout.  Even though most of the time it will be right, it is important to consult a tube manual or schematic at this point to verify that the pin out is correct.  After making sure it is correct and/or making any necessary changes, we can continue to the next part of the curve setup process, selecting the plate voltage.

Our choices range from 10 volts to 260 volts.  A chart is presented that shows the current limit of the B+ supply for any given voltage.  As you can see the maximum available current peaks at 150 volts, which is why 150 is the most common plate voltage used for testing.  You can exceed these limits by about 20% before the B+ regulation starts to suffer appreciably.  We decide to try a plate voltage of 180 volts.  Now, for the last part of the set up process, we need to enter the starting grid bias voltage and the amount to increment this voltage for each test.

This is the toughest part to decide on.  Use your best judgment based on your experience with the characteristics of the tube type being set up and the plate voltage you selected.  If you don't have any experience, don't worry about it, because you will almost certainly have to tweak the values later anyway.  In this case we are going to enter a starting voltage of -16 volts, and a voltage increment of 1 volt per test (more on why we picked these values later).  After entering these initial values we are now finished setting up the curve parameters for this tube.  The program automatically takes us to the curve trace test screen:

Actually, the screen you see here has already been edited with the final values decided upon by using a trial and error method.  That is why we don't see the bias for the first test starting at -16 volts and proceeding with 1 volt increments like we specified on the set up screen.  Since tubes are not very linear near cutoff, all properly set up curves have relatively large grid voltage increments for the first several steps.  As you can see, most of the grid bias voltage increments really are 1 volt apart once we get several steps into the tests.  When setting up new curves, pick a starting bias voltage based upon where you want the last test's bias voltage to be, not on where the first test will actually begin.  In this case it was decided to have the last test's bias at -1 volt.  Since there are 15 tests and the voltage increment is 1 volt, we started at -16 volts.  This resulted in the last test being at -1 volts (-16 + 15 = -1).  Note that not all curves need to be set up using all 15 tests, but the more we use the more accurate the results.  Most tubes need around 12 tests.

Notice there is an option for where to connect the suppressor grid.  If we are testing a pentode, we can connect it to either the cathode (normal connection) or the plate (triode connection).  If we wished to change this setting we would use the (E)dit command to do so.  The printed chart will indicate whether the curve was done in normal mode or triode mode.  The screen grid, if applicable, is always connected to the plate during these tests.

Lets quickly look at the commands available at the bottom of the screen.  First is (A)utoValues, which simply allows us to choose a different starting bias and/or increment voltage and then fills in the fields with these new values.  Use it to save typing if the bias values are so far off that they all need to be changed.  Next is (E)dit, which will allow any setting on the screen to be changed.  (Q)uit takes us out of the curve trace test screen and back to the normal test screen (pressing ESC does the same thing).  Finally, (S)tart actually starts the series of tests.  Lets press the "S" key see what happens.

Notice that the meter conversion chart is back.  It is not really necessary, but we can use it to tell how much B+ current we are drawing for the particular test we are on.  The numbers in the meter conversion section will turn yellow once the B+ power supply's rated current has been reached. They will turn red once 120% of the rated current has been reached.  If we reach the red numbers, then the meter readings cannot be trusted and we will need to edit the curve parameters to reduce the amount of B+ current being drawn.

Now that we finally have the curve tests underway we simply press button 2, note the meter reading, release button 2, then press the space bar.  The program will ask us to enter the meter reading before moving on to the next test.  If we need to go back to a previous test for some reason, we can press the BACKSPACE key.  It is easy to tell which test we are on because it is highlighted in yellow and has the applied grid bias voltage printed to the right.  This procedure is repeated until all the tests have been performed.

If at any time during this procedure we need to change the parameters of the test we are currently on (which we will since this is the first time this set of curve tests have been used and the meter sensitivity settings will almost certainly be wrong), we can press the "E" key.  This will allow quick editing of the bias voltage and/or the meter sensitivity of the current test only.  When setting the meter sensitivity, it is recommended that a value be selected that results in a meter reading of between 50 and 70 for a typical tube.  This gives an accurate current measurement while providing enough meter scale leeway to allow for unusually strong tubes.

Once all the tests have been completed, the program will ask to save the data.  When told "Yes", the program will prompt us with the tube's serial number.  This is simply a sequential number used to identify individual tubes.  It is also the name given to the file that the curve data is stored in.  The computer will automatically increment and remember this number, so we can just press ENTER to accept the number the computer assigns.  We also need to mark the tube itself with this number.

The last question we are asked is where to save this data file.  If the program is being run on the same computer that will be used to print the curves, meaning that it is a Windows based computer that has MicroSoft Excel loaded, then it is recommended to save the data files in C:\MYDOCU~1\  (the way DOS sees the C:\My Documents\ folder).  This is because the Excel macros look for the files there.  If the files need to be transferred to a different computer for display and/or printing, then save them to a floppy disk (A:\).  The program remembers where the last file was stored, so after telling it the proper location once we can just press ENTER to accept the default in the future.

During this whole procedure of editing and testing the filament power was always on.  This allows for quickly moving through the tests since no warm up time is needed between tests.  The filament power is not removed until either the tests are successfully completed and the data stored or the curve trace screen is exited.  There is a prompt displayed on the lower right portion of the screen that shows at any given time whether or not the filament is powered.

We are now through curve tracing this tube, and can move on to the next tube.  We can do as many as we like in one setting even if we are storing them on a floppy disk (the files are very small).  Once you get the hang of it you can create curves for a lot of tubes in a short time.  The macro that prints these curves will print all of them with just one keystroke.

Section VIII:  Setting up MicroSoft Excel for Printing Curves

This procedure gets the macros used for displaying and printing curves ready to use.  It consists of opening the macros in a text editor such as Notepad, then cutting and pasting into Excel.  This needs to be performed only once, and is done on the computer that will be used to print curves, which is not necessarily the same computer that is running the tube tester software.  Step by step instructions follow.

  1. Insert the original software disk in drive A:
  2. Open Excel
  3. Open Notepad (Start -> Programs -> Accessories -> Notepad)
  4. Click on File -> Open
  5. Click on the "Look in" box, and select A:
  6. Click on Dispcurv.txt
  7. Click on Open
  8. Click on Edit -> Select All
  9. Click on Edit -> Cut
  10. Switch to Excel
  11. Click on Tools -> Macro -> Record New Macro
  12. In the Macro Name field, type DisplayCurve
  13. Assign a shortcut key if desired (Control-D is recommended)
  14. Click on OK
  15. Click on Tools -> Macro -> Stop Recording
  16. Click on Tools -> Macro -> Macros
  17. Click on DisplayCurve then click Edit
  18. Click on Edit -> Select All
  19. Click on Edit -> Paste
  20. Close Excel, answering YES to save changes (Do not skip this step)

Now repeat the above procedure, this time using Princurv.txt in place of Dispcurv.txt, and use Control-C for the shortcut key.

Section IX:  Displaying and Printing Curves

Printing curves requires that the files created by the curve trace tests be stored in C:\My Documents.  If you are using the same computer for both testing and printing, then these files will already be there.  Otherwise, you need to manually copy them there.  The easiest way to do this is with Windows Explorer.  The filenames all have an extension of .csv.

Once you have the files in the My Documents folder, open Excel.  Use the following steps to display a single curve test on the screen:

If you wish to print all the curves stored in My Documents, simply press Control-C.  Make sure your default printer setting in Windows is correct first.  Once you have printed all the curves, you will need to either delete or move the .csv files out of the My Documents folder.

Section X:  In Case of Difficulty

The most commom problem is forgetting to connect the jumper to the plate current meter jacks.  Always check this first.

Support is best obtained through email.  Quick and concise answers to problems can be obtained this way.  Send email to:

You can also call during normal business hours, although many times you might get a machine instead of a human.  Email is usually quicker, but if you wish to call the telephone number is 405-340-9062.

Be sure to check the web site FAQ for answers to common questions.  Program updates and fixes are there too.  The web site address is: