Digital Tube Tester VS Analog Tube Test

[Billy Mayo]

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?

Use a 20,000 Ohm / Volt VOM To test Tubes? why a 20K ohm Volt meter?

 

[Reloadron]

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



How do you test filter caps with a VOM or DVM?

Use a 20,000 Ohm / Volt VOM To test Tubes? why a 20K ohm Volt meter?

Billy, the popular 5U4 and 5Y3 rectifier (dual diode) tubes share the same pin out. When using these tubes the filament serves as the cathode and each plate is an anode. The filament pins are 2&8 for both tubes. A 5U4 filament voltage of 5 volts and the normal current draw for the filament is 3 Amps. Therefore 5 Volts / 3 Amps = 1.6666 Ohms filament resistance. Pretty much a no brainer to measure the filament resistance and know if my filament is good. Pin 4 is Plate #2 and Pin 6 is Plate #1 so I should be able to measure between either filament pin (2 or 8) to pin 4 then pin 8 and read infinity (open circuit) using my meter. There isn't a hell of a lot to a dual diode rectifier tube to test it using a meter.

To test electrolytic filter capacitors using a VOM like a Simpson 260 set the meter on RX1 and connect the (+) lead to the cap + and the (-) lead to the cap neg. You will see the meter needle move up the scale. Now on a Simpson 260 use the polarity switch (AC + -) and switch between + and - watching the needle. You will see the cap slowly charge then discharge. While this is low voltage and will not show if the cap is breaking down it will tell you if the cap is open or not and if it behaves like a cap should. Matters not as to the 20K Ohm / Volt, that is the sensitivity of the Simpson 260 on DC voltage ranges.

Ron

 

[Billy Mayo]

The filament pins are 2&8 for both tubes. A 5U4 filament voltage of 5 volts and the normal current draw for the filament is 3 Amps. Therefore 5 Volts / 3 Amps = 1.6666 Ohms filament resistance.

So I set my DVM fluke meter to ohms? and put my meter probes on pins 2 and 8? it should measure 1.6 ohms?

But where does the 5 volts and 3 amps come from? my DVM fluke meter doesn't output this

Pin 4 is Plate #2 and Pin 6 is Plate #1 so I should be able to measure between either filament pin (2 or 8) to pin 4 then pin 8 and read infinity (open circuit) using my meter.

So Plate#1 should measure Infinity open circuit on my meter?
Plate#2 should measure Infinity open circuit on my meter?

While this is low voltage and will not show if the cap is breaking down

What will show the caps breaking down? what do you mean by breaking down?

How can you use a Simpson 260 to test a caps leakage or ESR?

 

[cowboybob]

There are some serious, basic electronics misunderstandings here...

Billy, a few quick quiz questions for you:

Using Ohm's Law:

1. If you had a 10 ohm resistor attached to a 5 VDC source, what would be the current flowing in that circuit?
2. If you had 4 amps flowing in a circuit made up of a 10VDC source and a resistor, what is the value of the resistor in ohms?
3. If you had a 15 ohm resistor with 3 amps flowing through it, what is the level of the voltage source?

Note: you could manually derive the answers using virtually any VOM.

 

[Reloadron]

To quote the infamous cowboybob:

There are some serious, basic electronics misunderstandings here...

Billy, if you have any aspirations of any form of a career in electronics you need to start learning the basics, starting with basic theory as in EL-101. If you have any aspirations of being able to work on vacuum tube / valve type amplifiers I suggest you forget about tube testers and start with the fundamentals of how a vacuum tube works, even the simple ones like a diode tube. However, basic DC Theory comes first.

This is a data sheet for a 5U4 common dual diode vacuum tube. Note the tube drawing and look at my post. The data sheet tells us the typical filament voltage is 5 volts and the filament current is 3 Amps. The filament is between pins 2 & 8 of the tube base. Knowing two of three variables (5 Volts and 3 Amps) I can apply basic ohms law and derive the filament resistance. Voltage / Current = Resistance. Therefore 5/3=1.66 Ohms so call it 1.7 Ohms. If I measure between pins 2 and 8 I should see about 1.7 Ohms and I don't need a tube tester to tell me that and most won't.

So, what are the answers to cowboybob's questions?

Ron

 

[Billy Mayo]

1. If you had a 10 ohm resistor attached to a 5 VDC source, what would be the current flowing in that circuit?'

500 milliamps

2. If you had 4 amps flowing in a circuit made up of a 10VDC source and a resistor, what is the value of the resistor in ohms?

2.5 ohms , 50 watt resistor

3. If you had a 15 ohm resistor with 3 amps flowing through it, what is the level of the voltage source?

45 volts

 

[Billy Mayo]

Pin 4 is Plate #2 and Pin 6 is Plate #1 so I should be able to measure between either filament pin (2 or 8) to pin 4 then pin 8 and read infinity (open circuit) using my meter.

So Plate#1 should measure Infinity open circuit on my meter?
Plate#2 should measure Infinity open circuit on my meter?

While this is low voltage and will not show if the cap is breaking down

What will show the caps breaking down? what do you mean by breaking down?

How can you use a Simpson 260 to test a caps leakage or ESR?

 

[ChrisP58]

So Plate#1 should measure Infinity open circuit on my meter?
Plate#2 should measure Infinity open circuit on my meter?

​

What will show the caps breaking down? what do you mean by breaking down?

How can you use a Simpson 260 to test a caps leakage or ESR?

Yes, the plate should measure open circuit to the filament.

Voltage breakdown on a cap is when you reach a voltage where it starts to conduct DC current. To test that you need a current limited power supply voltage higher than the rated voltage of the cap. If the breakdown voltage is lower than the cap rating, then it is bad.

You can't test ESR with a Simpson 260, or any standard multimeter.

 

[Billy Mayo]

Voltage breakdown on a cap is when you reach a voltage where it starts to conduct DC current. To test that you need a current limited power supply voltage higher than the rated voltage of the cap. If the breakdown voltage is lower than the cap rating

If you put a higher voltage than the Caps rated voltage it will damage the cap right?

How would you know that a cap is conducting DC current? do you need to use a DC amp meter?

You can't test ESR with a Simpson 260, or any standard multimeter.

Yes I know, AT work i use a LCR meter to test the ESR

I mostly get .02 to .05 on the ESR readings. How do you know what is good and what is bad ESR?

the plate should measure open circuit to the filament.

This is just for the Rectifier tube right? or for preamp tubes and power amp tubes?

 

[cowboybob]

1. If you had a 10 ohm resistor attached to a 5 VDC source, what would be the current flowing in that circuit?'

500 milliamps

2. If you had 4 amps flowing in a circuit made up of a 10VDC source and a resistor, what is the value of the resistor in ohms?

2.5 ohms , 50 watt resistor

3. If you had a 15 ohm resistor with 3 amps flowing through it, what is the level of the voltage source?

45 volts

Excellent. 100% Nice addition of the resistor's wattage requirement on question 2 .

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