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Digital Tube Tester VS Analog Tube Test

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The Digital tube tester , test the tubes at high voltage at 300 volts to 400 volts VS Analog Tube testers, test the preamp or power amp tubes at lower voltages?

Testing Tubes on an analog tube tester will PASS the test because the analog tube tester is testing them at a low voltage. But you slap those tubes that have passed the test and they will fail in the preamp or power amp because now they are in a 400 volt circuit.

Why do they fail with high voltage but now with low voltage?

Analog Tube testing , doesn't test the preamp or power amp tubes for Noise or Hum? but does a digital tube tester test the tubes for hum and noise?

The Digital tube tester , test the Plate current and Transconductance of a power tube, which analog tube tester don't?

Does an Analog tube tester, test the Transconductance of a preamp or power tube? I don't remember see a function on my analog tube tester

Power Tube Digital Tester:
**broken link removed**

Pre-Amp Tube Digital Tester:
**broken link removed**

  • Listen to your tubes with dual-RCA Direct Audio Output? is this to test for the NOISE of the preamp tubes?
 
Only audiophile wonks who can hear the sound difference between two different types of copper in their speaker cables worry about technology that's been obsolete for 50 years. :rolleyes:
 
Tube tester, Transistor tester, have the same problem. They need to be low cost and test most parts with out damaging any part. Most transistor testers test at 3 volts or less, (less than 9 volts) because some transistors are only rated for 12V, and because many are only powered by a 9V battery or two AA batteries.

Testing for hum is not a function on any tube tester I have seen. I remember on some high end testers have a filament leakage test that might be the same thing.

My DVMs have a transistor tester function. They test NPN/PNP and if the part has 'any gain'. It can not check to see if the part has the right gain at the right current. It does not test leakage or any high voltage conditions. (no high frequency test)

I have used $2000 curve tracers that test for many functions. You really need to test the part (tube or transistor) at all conditions that it might be used at. (low/medium/high voltage) same for current. At least test it for the condition you will use it at. Your tester needs to have a supply voltage as low as 12V for the little RF tubes and as high as 1000V. (how will we test the 10kv tubes?) You need a supply that can handle current over a large range. Many different types of loads. This is too much for a low cost tester. Too much for a high cost tester. Most people need a "go/no-go" test. Is the filament there? Is there any gain? Is there tooooo much leakage. and test at some safe low voltage and small low current.
 
The analog tube testers would have a LIFE test, you push a button and it would but a Load on the tube to make sure it was not Weak

I don't see this feature on the digital tube testers , do you guys ?
 
Why do you need to balance the GM? what does the GM do?

I don't remember my Analog Tube Testing , testing the GM Transconductance of my tubes? was it called something else?

The Digital Tube tester, tests the Plate current

I also don't remember my Analog Tube Tester testing the plate current

My Analog Tube tester had a button to do a LIFE TEST which would load the tube and see if it was weak or not

I don't see this Digital tube tester doing that right?

search
 
So the LIFE TEST is testing the filament? or the filaments voltage?

Why doesn't this Digital Tube Tester test this?

So if the Tube has BAD GM conductance , what does this mean? the tube doesn't have much gain or the output of the tube is low?

I use to test tubes on an Analog tube tester, it just tested the Emission of the tube

The Digital Tube Tester tests:
1.) Transconductance which is GM?
2.) Plate Current

An Analog Tube Tester doesn't test a tubes Plate current right?

It test the Tubes plate voltage either at 350v or 400v, an analog tube tester doesn't test tubes plate voltages at this its at 25 volts or lower right?

Does analog tube tester bias power tubes at -60, -48, -36, -24, -14 ?
 
What does it matter?, valves are long obsolete, valve testers are worthless and you can't even give them away.

But regardless, ALL testers only test a very limited degree of functionality, it's no proof that it's OK - although it 'can' be proof it's faulty.
 
Beyond the displays on the linked to tube testers what exactly distinguishes a digital tube tester from an analog tube tester? What am I missing? I don't get this analog / digital thing.

Looking at the cost of the linked to tube testers if I were to want to revisit the world of testing tubes I would think about investing in an old TV 7 ( )/U series tube tester on E Bay or from another source.

A few of the young engineers I worked with were into tube type amplifiers for their guitars. Looking at the limited number of tubes supported by the linked to testers my guess is they are aimed at the audiophile market. The 12AX7 preamp followed by a 6L6 output stage. Given a choice when I worked on amplifiers these young guys owned I used a DMM and Scope. Not difficult to inject a signal and signal trace those amps.

As to tubes? I found this PDF online of a circa 1960 book. Not a bad read at all for someone with an interest in vacuum tubes or for my friends across the pond, valves.

Finally I agree with Nigel in that a Tube or Valve tester really doesn't tell you very much as to how well the component will function for its intended use in a circuit.

Someone who works with tubes all the time, possibly repairing tube type amplifiers should just build their own test jigs.

Ron
 
Someone who works with tubes all the time, possibly repairing tube type amplifiers should just build their own test jigs.

No need - you don't test 'components' you test 'circuits' - so there's no need or point in testing a valve outside of the circuit it's used in.

Back in the old days (when valves were still used) we had a valve tester at work (it got destroyed in a fire a bit later on), but it was NEVER used for doing repairs in the workshop, it's sole use was testing valves for customers who brought them in (presumably like American drug stores used to?).

We've fairly recently acquired a similar Mullard Valve tester to the one we used to have from a bankrupt dealer we cleared out, I'm not sure if we've binned it or not?, as there was zero interest in it.
 
No need - you don't test 'components' you test 'circuits' - so there's no need or point in testing a valve outside of the circuit it's used in.

Back in the old days (when valves were still used) we had a valve tester at work (it got destroyed in a fire a bit later on), but it was NEVER used for doing repairs in the workshop, it's sole use was testing valves for customers who brought them in (presumably like American drug stores used to?).

We've fairly recently acquired a similar Mullard Valve tester to the one we used to have from a bankrupt dealer we cleared out, I'm not sure if we've binned it or not?, as there was zero interest in it.

And this is why I mentioned a DMM and a Scope. :)

No need - you don't test 'components' you test 'circuits' - so there's no need or point in testing a valve outside of the circuit it's used in.

I would only add Amen!

Ron
 
The Digital Tube tester , test Power Tubes at 400volts just like it would be in circuit

Yes Analog Tube testers are worthless to test tubes
 
So the LIFE TEST, is testing the Cathode? cathode's chemicals?

Analog Tube tester
1.) Test The Grid Emissions
2.) Test the Grid Leakage
 
So the LIFE TEST, is testing the Cathode? cathode's chemicals?

Analog Tube tester
1.) Test The Grid Emissions
2.) Test the Grid Leakage

One more time, the only difference between an analog tube tester and a new super duper digital tube tester is the display. There are analog tube testers that also have 400 volt and higher B+ plate supplies. The term "Digital" as it applies to a tube tester is no more than a marketing term.

Typical grid current in a triode vacuum tube is very low as in tiny as in nano amps. During normal operation as a tube functions, with a focus on a basic Triode tube, when energy in some form is applied to the cathode (heat energy) electrons are released or as some say cooked off. There are several methods used to heat the cathode (filaments) and we won't get into them. The cathode is a thin metal sleeve coated with electron emitting material such as alkaline earth oxides. The cathode, again, is heated by the filament. Over the life of the tube tiny micro particles of the cathode coating get emitted with electrons and smash into the grid. While over simplified this is what happens especially when tubes are pushed beyond their normal operating limits. When this happens the normally tiny grid current begins to increase. Grid leak current is inherent to the normal operation of the tube, only when this normally tiny current increases because of chunk emission of cathode particles does problems begin. If you want to test for excessive grid leakage then look at the grid current. Personally I believe the following quote to be true as stated.

Grid leakage is also a term that is frequently incorrectly used to describe the condition of a tube when tested on a tube tester. The correct term is inter-electrode leakage, which refers to leakage paths between the elements of a tube. Many emission type tube testers have leakage tests that far exceed the application of the tube being tested and will reject many perfectly functional tubes. Sencore sold tube testers in the 1960s that were claimed to have the "most sensitive leakage test in the industry".

As to life test? If you were to look at a schematic of most tube testers that have a life test button you would find that most simply reduce the filament voltage by about 10%. They do this by using a button switch to place a power resistor in series with the filament voltage lines. So a 6.3 volt filament now only sees 5.67 volts and a 12.6 volt filament now only sees 11.34 volts. The theory here is a good healthy tube should not drop below 90% of its operating characteristics. Personally I see this as more hype than anything else but if people choose to see useful information in this form of life test, then cool with me. So as to the cathode in a life test? Normally a cathode is heated to around 1050 Degrees K. Now obviously if we reduce the filament voltage 10% the cathode will run at a lower temperature. The question is running at a lower temperature how well will the cathode emit electrons?

The true test of grid leak current of life test is how well a tube is functioning in a circuit it was designed to function in? This is why most savvy engineers and technicians prefer to actually look at a tube in circuit using good equipment to evaluate the tube performance.

The attached below image should give an idea of what is going on. The purple trace I[V3} is the grid current, note it spikes as the tube goes into conduction. The Green trace is Vin and the Red trace is Vout. Vout starts to grow in amplitude as the filament heats the tube cathode up and it begins cooking off electrons. Conduction begins just beyond 4 seconds.

12AX7 Test Configuration.png

Ron
 
Yea but what if you had internal shorts inside a preamp tube or power amp tube or a tube rectifier and you were to turn the amp on , it wouldn't work and then the preamp section board at certain stages wouldn't work , so you have to use an oscilloscope to track it down

Plus if the tube rectifier is has shorts or other problems it will cause the amp to blow fuses

A Tube Tester HELPS you out with this stuff to Cut down the troubleshooting
 
Yea but what if you had internal shorts inside a preamp tube or power amp tube or a tube rectifier and you were to turn the amp on , it wouldn't work and then the preamp section board at certain stages wouldn't work , so you have to use an oscilloscope to track it down

Plus if the tube rectifier is has shorts or other problems it will cause the amp to blow fuses

A Tube Tester HELPS you out with this stuff to Cut down the troubleshooting

I guess what it all comes down to is I grew up in the 50's when the first transistors were being developed and coming available. My earliest education in electronics was pretty much all vacuum tube theory and circuits. For me I never had an overwhelming desire to own or use a tube tester, however, did use a few over the years. I mentioned the old TV7 series earlier. I am just one of those people who is comfortable tossing a vacuum tube amplifier or any other number of tube type devices on a bench and using other shop instruments to trouble shoot it. My opinion and just my opinion is I can just as easily do a fault diagnosis without a tube tester. However, if someone is more comfortable using a tube tester then cool with me. Be it a tube tester, VOM, scope they are all just tools. Use the tool you are most comfortable using.

Yes, I agree if a rectifier tube has shorts or other problems it will cause the amplifier to blow fuses. The most common rectifier tubes are likely the 5Y3 and 5U4 tubes. Both have the same pin out with the 5U4 rated for higher current. I have two plates and a single filament. I can yank the tube measure filament resistance and continuity test either filament pin to the plate pins in a min using a VOM. The majority of power supply failures I have seen have been failed (shorted) filter capacitors blowing fuses or failed (open) filter capacitors allowing a ripple component and audible 60 Hz. (US) hum in the output. The latter easily seen on a scope or testing the filter cap with a VOM.

So while you see merit to the tube tester I just do not. Matters not as we use what we are comfortable using.

Just My Take....
Ron
 
the 5Y3 and 5U4 tubes. Both have the same pin out with the 5U4 rated for higher current. I have two plates and a single filament. I can yank the tube measure filament resistance and continuity test either filament pin to the plate pins in a min using a VOM
.

Explain more about how you can test TUBES using a VOM or DVM?

testing the filter cap with a VOM

How do you test filter caps with a VOM or DVM?
 
Tomorrow I'll toss more out on how I go about it.

Ron
 
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