got given a Acturus "BLUE" globe 127 marked Detector tube today.put it in my tube tester to check it out and something happened with the tester and it suddenly sent a shot of voltage through to the tube and made it go real bright and before I could shut it off the tube made a flash and I guess is now junk.guess now it is nothing but something for display.just my luck.the tester is the only working one that I have that tests 4 and 5 prong tubes.guess that is junk now too.

If it burned out a filament it must have been a major malfunction. Even a shorted line rheostat shouldn't have placed that much voltage on a filament. Are you certain the filament didn't sag and touch the cathode? If so, the tube was a goner anyway.

not sure what did happen.it happended when I was adjusting the line on the meter before starting the test.

I agree with Johnnysan's observations, 100 percent. Adjusting the line
calibration would hardly account for this sort of failure. Unless the filament
voltage setting was grossly mis-set, there is no logical explanation for the
tube failure.

Pete

Tube must have had some sort of internal short. If you bought it as a working tube online, you might see what you can wrangle out of the seller. Although usually the internal shorts test is the first thing to do.

I suggest that a dummy 5-pin plug set up with a 2.5 volt lamp as a filament load. Then attempt to duplicate the disaster settings and try and roast the lamp. All the while paying strict attention to what control is being manipulated.

YMMV

Chas

It's an easy mistake to make for even the most experienced tech/restorer. I always try to remember to turn the filament voltage down all the way when I finish testing tubes and to check for it when I begin to do more tube tests.

Blue 27's are rather common so it's not a great loss. Had it been a blue audio tube, you would need to take away my belt and shoe laces.

Pete

So then how are you supposed to adjust the line voltage control? The manuals for every tube tester I've ever owned tell you to bring the needle to the mark with the tube in, so you are adjusting for the heater load.

Basic emission testers often have voltages applied at all times, so no switches or controls should be changed on those while a tube is in a socket. But better quality testers do not apply voltages until the "Test" button is pressed, so it is perfectly safe to change settings as long as you are not holding the button down. Of course, one had better make sure the heater voltage is properly set before plugging a tube in, but that goes for any kind of tube tester.

The 27 tube has a 2.5-volt, 1.75-amp heater. This is a strain for the transformers on many tube testers. Consequently, it is doubtful that the line voltage control on the OP's tester would have had enough range to cause the tube to burn out. It is far, far more likely that the filament was brittle from age and handling, and it simply broke. Happens to everybody sooner or later.

Noted but I'd recommend doing the following:
Set the load control and all the other settings FIRST, then double-check to make sure they are right, then plug tube in, let it warm up and then re-check the load setting before doing the actual test.

Never had a catastrophic failure doing that.

Then, you've never had a Hickok TV7.

It's right in the manual... to push the button, and adjust the line voltage control to bring the needle to the center mark, AFTER putting in the tube and turning on the tester. The readings are WORTHLESS, unless you do this... you have no idea how they compare to standard. Might as well not bother to calibrate the tester in the first place, unless you are willing to actually follow the instructions...

That's how the US Army did it for MANY years...

Regards,
Gordon.

This makes no sense at all. After making all the sure all the setting are correct i install the tube. Depending on how much current the tube is drawing you will see the meter move. How can it be possible to set the meter without any load on it? Have to ask you a question. What is with the font color? Do you like blue?
Stan Ski

Many testers require the line be set after inserting the tube... It can be set prior but as mentioned when the tube is inserted there will be some voltage sag so setting will have to be increased... On my old Precision 920 I know approx how much increase is necessary, unless it's a battery operated tube, I set it slightly high and it usually only needs a minor tweaking...

My B&K707 automatically sets line, uses two #55 lamps to monitor line current similar to some Hickoks...

Tom

I have a triplett tester.you have to bring it up to line then use other knob and turn left or right for the basic tests.today it seemed to do what it was supposed to.

For the Heathkit IT-17 Step 1 says to adjust the line control without the tube in the socket. Step 7 says to readjust the line control after the tube is installed.

This is normal procedure for many tube testers.

Dave

An IT-17 is an emissions tester, is it not? I wouldn't think that it would be as critical as a good Dynamic Mutual Conductance tester, like the TV-7 mentioned above, or my Hickock 539 or my trusty old I-177B. Emissions testers were the dope back in the early 'thirties, but by the time the War came just about every tech who could afford one jumped for the more sophisticated unit. A dynamic tester is also helpful when selling tubes. Back when I was flogging fifty to seventy high-end audio tubes a week I found it worthwhile to pick up a calibrated Hickock 600 (a less sophisticated contemporary of the 539) at some considerable expense simply because many of my prospective customers in the former Greater East Asia Co-Prosperity Sphere were familiar with that common unit.

As for the line adjustment, well I've been adjusting the line adjustment whilst the power transformer is under heater load AS PER TESTER MANUFACTURER'S INSTRUCTIONS for nearly forty years, now, ever since I picked up my first surplus I-177B when I was in fourth grade. Never had a tube go out while under test due to incorrect line adjustment, either, even though I've always tended to test a lot of the more delicate stuff, '99's, WD-11's, 101F's, 216's etc.

I would assume that as long as one's tester is reasonably well calibrated and one follows the manufacturer's instructions, and the tester os of reasonable quality one will get reasonably repeatable results. Of course, even the best tester offers only a general gauge of quality. many weak tubes perform well in certain applications, and some strong tubes don't perk very well in others.

What sort of tubes do you deal with, by the way? Early stuff, or the late heater cathode things?