Questions tagged [tube]

The word "tube" may refer to a broad range of engineering items, including electron (vacuum or gas) tubes.

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1answer
117 views

Troubleshooting Hum in a Tube Guitar Amp

I have a Fender Deluxe Reverb Reissue guitar amplifier that hums whenever I turn on the reverb. It sounds like loud 60 cycle hum. The reverb effect is still applied, but is accompanied by the hum. ...
0
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1answer
83 views

How to measure the output impedance of a valve preamp?

I was trying to measure the output impedance of a DIY preamp for the past couple of days without any luck. Each time, I got to the same result of around 3K3 ohm, which is unbelievably low. This is ...
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2answers
65 views

Replacing elements in a tube amplifier

I assembled a tube amplifier.According to the specified scheme (Old Russian radio "Record 66"). 1.What is the function of capacitors C9 and C8 ? 2.What will change the capacity of these parts? Will ...
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0answers
103 views

Identifying Noise in 12AU7 Based Headphone Amplifier

I've been working on making a tube based headphone amplifier as a fun personal project. The amplifier is based around this 12AU7 vacuum tube. The project for the most part is following this existing ...
1
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0answers
126 views

Magic Eye Tuning Tube Variable Negative Voltage

I am thinking about several applications of magic eye tuning tubes as display pieces and had a question about their operation. I have attached a sample circuit from a datasheet for an EM84 tube. I ...
5
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2answers
423 views

UHF Tesla coil powered by low voltage?

I want to know if it is possible to use a 2.4 GHz magnetron as a oscillator for a Tesla coil circuit. The idea is to use a oscillating relay-driven step up transformer (12 V to 10 kV) and then charge ...
1
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2answers
484 views

What is a ESD tube?

In the ESP32 datasheet, what do they refer to with "ESD tube"?
0
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2answers
58 views

covering sides of LEDS without adding heat

I'm doing a project in which a 5mm LED is near a 5mm phototransistor. There are times in which the sensor must pick up external light even with the LED on. I understand one option is to turn the LEDs ...
1
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1answer
172 views

Tube amps on voltage regulator

I have one basic question, because I don't know much about tube amps. I live in a country where during winter, voltage can be from time to time low (around 160V-180V). I decided to keep my amp safe ...
2
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1answer
223 views

an/prm-10 grid dip question - how the voltage can be negative at the grid? [duplicate]

I am trying to repair a recently bought AN/PRM-10 grid dip. I have replaced some electron tubes by new ones and (almost?) everything seems to be OK regarding the voltages at the pins of the electron ...
4
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3answers
766 views

Open-air electron tube

So, I know that vacuum tubes only work because they're, well, a vacuum, and gas-filled tubes have a hysteretic effect relating to gas ionization. My question, however, is this: Would an open-air '...
0
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1answer
558 views

Preamp for Magic Eye VU meter [closed]

I want to build a Magic Eye Tube VU. This tutorial http://www.antimath.info/electro/vu-meter-em84/ says: If this circuit is used with a tube amplifier, the “IN” connection in the picture is ...
3
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2answers
514 views

12 - 330v boost converter

I recently bought a G10/241E tube and I need a power supply for it. There are no designs of a 330V DC power supply and no buck-boost converters would work with such voltage. The datasheet and example ...
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3answers
3k views

Triode - how come grid is “more negative” than cathode?

This is probably the most lame question of all the time here, but... I cannot understad grid-cathode "negative" polarization. For me, grid is always positive to the cathode. I mean, in practice, ...
8
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3answers
2k views

Why are thermionic valve/tube heaters generally designed to be 6.3 V?

Why are the heaters generally 6.3 V (or multiples thereof)? Does it make for an easy transformer winding ratio when used in countries with 120 VAC or 240 VAC mains? They often pull quite ...
0
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1answer
3k views

Compatibility & Interchangability of KT88, KT100, KT120 and KT150 Tubes in Tube Amplifiers

Are (immediately from the start or over time) the tubes that come with a tube amplifier (say the popular KT88 in Single Ended mode or Push Pull mode) replaceable with say the larger KT120 or KT150 any ...
3
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2answers
248 views

Replacement for tube-based trigger switch (Thyratron) in high-voltage supply

A now-deleted question asked whether it's possible to replace the trigger in a specific application (laser supply, source here): and other things. For me, it boils down to a single, less ...
1
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2answers
501 views

Why the current in X ray tube is in milli amps

If we see a X ray generating tube the voltage applying to tube is in kV, but the tube current is in milliamps. Why this current is in mAs not in amps?
2
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4answers
1k views

Step down transformer for vintage tube amplifier

Hi so I've just bought a 60's tube guitar amp from the U.S, I live in Australia. Through searches across the internet I've found a few potential issues with the safety of running the amp through a 240-...
0
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1answer
292 views

CAM 5 LASER CUTTER : needing to change the laser tube [closed]

My boss and I discovered that one of the laser tube needs to be changed, and when we figured which one needed it, I told him not to touch the red wire, that there may still be power in it. Well he did,...
0
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2answers
1k views

Tube amp low voltage [duplicate]

I am building a 18W tube amplifier based on this layout. I found a schematic for a similar amp. my problem is that there is low plate voltage on all of the tubes (by plate I mean pin 3): when I ...
0
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2answers
275 views

What component: a glass tube wrapped with a wire mesh and has a single metal pole inside?

I found this while trying to fix my noisy hot/cold water dispenser. It has a blueish glow and makes a loud buzzing noise of around 56-58 Hz. I'm planning to replace it, but there doesn't seem to be ...
0
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2answers
371 views

Guitar Tube Amp RC Filter frequency fluctuation

In a simple LP or HP RC filter, is there a scenario where the centering frequency can fluctuate? So say the filter is a low pass and its set to pass everything up to 800hz, is there a situation where ...
2
votes
1answer
149 views

Gas Tubes: neutralization of space-charge causes drop in tube resistance? Deionizing voltage re-combination?

The following paragraph is from Chapter 3 of the book Principles of Electronics. When cathode is heated, it emits a large number of electrons. These electrons form a cloud of electrons near the ...
3
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1answer
132 views

What is a Reacto Tester unit and are there any projects in which I can use it?

I was given an old piece of electronics. It is a Reacto Tester made by Antronic Corp from Chicago. After a quick glance at the manual it seems that its a tester for tube display units such as ...
7
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5answers
15k views

Vacuum tubes heaters supply, AC or DC?

Which way is better to feed the heaters of a vacuum tube on a guitar amp, AC or DC? With the same transformer, is it possible to change between AC and DC supply for the heaters?
2
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3answers
13k views

How do glass tube fuses work?

This may be the an unspeakably stupid question for an electrical/computer engineering student to ask, but I ran across a few parts I didn't recognize (which, after some research, I found out were ...
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4answers
5k views

How can I repair my old tube TV safely? [closed]

I got an old Nokia tube television from my grandmother. I tested it, but there is no picture. I can hear the audio. The filament is not glowing. I am studying EE, but there I only dealt with low ...
8
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1answer
2k views

Thyratrons: How they work, what they are used for, and how to read their datasheets

I recently ran into an interesting device called a thyratron. I have a basic understanding of thyratrons as gas filled vacuum tubes. I understand that they can switch large amounts of currents and ...