[fields 100]

I am trying to understand the purpose of this tester.It is recapped and calibrated and it works, but in some strange way. For example, I have 2 globe 47s, which are very weak, I bought them as such. Using the tester, one shows 70%, another 80%. So, I am elated for a moment.Putting each of them to one of my sets- the volume as well as reception drops 50%. Any ideas?
Realizing it is a cheap tester, one should expect better than that.Thanks.

[Phlogiston]

For power output tubes a good mutual conductance tester is the best bet.

[morzh]

If tube has emission it simply means the tube is alive and will likely function.
However only mutual conductance gives you the measure of amplification the tube can provide.

Although I myself not quite sure what makes a tube lose conductance without losing emission. But then I do not know tubes well.

[fields 100]

Then away it goes.

[gregb]

I have both types of testers, emission and mutual conductance. I find a person needs to understand his tester and it will serve you well no matter which type it is. The best tester is the equipment it is to be used in and you use a tester to make sure there are no shorts, there is some amount of emission and maybe do a gas test. With my emission tester I can tell if a power tube is good or not based not on the end reading but on how fast it gets to that reading. If it goes to 90 on the scale within a few seconds of testing, it will test great on the mutual conductance tester and most likely do the job in a set. If it still tests up in that 80-90 range but takes a couple minutes to get there it will not test good in the mutual conductance tester and most likely will have an issue in the set but not always. It will depend on what the set design expects the tube to do. A lot of sets are designed so the tubes just idle along without any real stress on them where as others have a tube running at its extreme limits. A weak tube will work fine in the first application but will fall on its face in the second.
Understand what you tester is telling you and what your equipment expects of the tube and any tester that is working as designed will give you usable results.

Gregb

[fields 100]

Gregb

It is interesting. I will check the tubes again and time it. Do I have to give it a chance to warm up, then press the test switch and time it or start timing immediately? However, providing that the mutual conductance tester is affordable for one, what is the point of having the emission one? Is it the ease of use, say, during the service call or anything else?

[morzh]

Well....even today i can take an arrow Ohm-meter and tell you if an electrolytic cap is good or bad just using it alone.
I however much prefer to use a C-meter, and, when warranted, also measure leakage and such.

And in fact I knew a person who (having some genetically explained) high body resistivity could tell a live wire voltage just by holding in in his hand while touching the Earth with the other one.
I myself can tell a battery voltage up to 9V by putting my tongue to it

This said, unless the money is an issue, I always prefer tools created or at least well-suited for particular job, so it does not require adding my own personal special skills.

Now, if for what you do, this type of tester is sufficient, use it. If you feel you'd rather have direct answer to your questions, use another one.

Just an opinion.

[gregb]

I actually use three different testers on a regular basis depending on a number of factors.

The warm up time of a tube depends on the tube, a directly heated cathode should be up to full temp within a few seconds of power on. An indirectly heated cathode could take up to a minute or more depending on the tube design. Some tubes had controlled warm up times.

A lot of what I say is 30 years of testing tubes and just my experience with doing it and using my testers. If you really have an interest in doing this then there will some experimentation for you to carry out. You will need new tubes as reference and have some bad ones to see how they react in your testers and your equipment.

The other thing is just because a tester says a tube is good really means nothing until it works in the set. I have a 47 tube that I broke the seal on its box and tested and it was 100% as I would have hoped and installed it in a radio and had zero output. I did some trouble shooting and it appeared the tube was bad so swapped it with another known good tube and the radio played great.
I retested the original tube and it still tests 100% but will not work in a radio.

Have fun and don't be to quick to judge your tester, it might be doing what it was designed to do and some do it better than others for sure.

Gregb

[OldRestorer]

I have been looking for a tester for a while now. I look and look but havent gotten one. I have my grandfathers but it does not work.

This week I took it out and read up on it. Guess what? It does work and I am just dumb. Learn the tester before testing is my new motto... for today anyway.

I actually did get a great little tester from Sam so I can test many on his and the rest on my grandfathers..

[fields 100]

Thanks guys,
Now I am COMPLETELY lost, lol.
Someone on the Phorum have suggested some time ago, that the best way to check the tube is to switch it with another, known good one taken from the working set, or change places, whatever. Come to think of it, it makes healthy sense.Sounds like even Hickok may hick up at you.At this point, for some unknown reason all my tubes, from the sets and the spare ones test "like new". Too good to be true.BTW, I just checked the 2 of my 47, the week ones, the needle jumped to the 80% almost immediately.As much as I love attempting and sometimes succeed repairing the radios, I can not stand unreliable tester. And I love analog testers.Another day somehow ruined mine from 1963, had it for 30 years. There have been 24 hrs mourning.

[gregb]

It does sound to me like there may be an issue with your tester. Who did the repairs and calibration, are you confident in their workmanship?

Gregb

[fields 100]

There was no need for repair. It came operational. I replaced one cap (may be 2, can not recall) and calibrated it as per instruction. The piece is as simple as it can be. It was some time ago, but I believe there was only one pot to work with.All switches operate and the neon light works for "short". The filament voltages are correct.

[gregb]

Did you check the resistors? I find the resisters in tube testers are always way off and you want them as accurate as can be.

Gregb

[fields 100]

I'll follow up on that. Can't remember, but check all the same.
Thanks.

[codefox1]

Time Out! A tube tester can try to heat up the filament, check for shorts within elements, do a rough check of cathode-plate effieiency at diminshed voltages as a erzatz rectifier, and perhaps indicate or point to other anomolies of the grids or overall polution of the assumed "perfect" vacuum.

Did you ever hear the difference in a tired old AA5 when a much better 50XX was subbed? I did.