Burning in tubes with the AT1000 tube tester

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The advantage of AT1000 is, it can run continuously under full power. Which only very few devices can do. However, because if a missing burn in routine, it has to be done by hand

First you need to set up the AT1000 better. Factory set up in not done right. Get yourself some old, used, single system triode from your collection. So no double triodes. You can do double triodes or expensive NOS later, but now first comes setting up of the system.

PART1 STAND ALONE MODE

I am always surprized again to see that appr 50% of the users do not use the computer mode, because you are missing the best of the AT1000. This first part here, is for stand-alone mode users.

First thing. For burning in virgin NOS tubes, such which were in the boxes ever since 50 years, first comes cathode cleaning. This is done by running the tubes with heater only, and not tube testing yet. The AT1000 can not do this in stand alone mode. So you need some kind of other tube tester, or other way, to achieve this. Run time is 15 minutes. Some use 10% more heater voltage. I recommend normal voltage, unless burn in, in the next step, is not successful. In such a case, you could repeat step 1 with 10% more heater voltage.

Second thing. You need to set your AT1000 in general to AUTO BIAS. The factory has set it to FIXED BIAS. This is wrong for general testing, and specific for burn in, it is more wrong. To change this, keep the left arrow key pressed while switching on the tester at the same time. Now comes the menu, and you need to keep on hitting the arrow key, to skip to “bias method”, and then change it to auto bias. Then switch the tester off. Switch on again, and check if a tube is tested auto bias now indeed. So this has to work first.

Third thing. You need to change the test method from automatic (timed) to “manual”. Same as above, with the left arrow key. After it was done, switch off, and switch on again, to check if testing is not “timed” any more, but was changed to 'manual' indeed. So this has to work first. In manual mode, the tube warms up with plate current, as long as you say, before testing. (In timed mode, it is timed automatically)

If these things are done correct, you can give it a try with a tube inside. So the tube will warm the heater first, and then the tester goes into auto bias mode. You can see in he display the tester will change the grid voltage, until the specified plate current is reached. In manual mode, as the tester in now, it will STAY THERE forever, until you stop it, and you MUST stop it.

There are two reasons to stop.

1) Emergency. That is when current rises more than 15% .
2) Burn in is finished, and you continue to final testing.

It is very important to keep on watching it, because AUTO BIAS forces a tube to 100% current, even when the tube is 60% only. However, now burn in begins. So after the tube reached 100% quickly, you will then see plate current rise slowly, above 100%. The minutes not much, but once burn in l begins, it will go faster. Plate current will rise…. 105%.... 110%.... 115%... However now, the tube begins to over heat. So at 115% you must stop with the “< Key” it is the emergency stop. Now, you do the test again, and the tube will restart at 100% and begin to rise again. Stop again at 115%. There will not be so many repeats, because each repeat adds 15% emission. So at some point it takes longer before again 115% is reached, or it will stabilize below that. If so, burn in is finished. Note, plate current indication is in mA, you need to calculate before you begin, what is the 115% limit in mA. Basically, 100% is the value the tester starts with.

After burn in, test the tube in auto bias mode, and go to “Next” if the tube becomes stabile, but not before 60 seconds. Now, Gm must be in specified range, and then the tube is good.

Best is to learn how to do it with some already used tube and not sacrifice expensive NOS for learning by doing.

PART2. COMPUTER MODE

USE THE TEXT OF PART1, so see what you have to do, but operation is now easier.