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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NE-77 neon glow bulb trigger electrode as signal source?
The NE-77 neon glow lamp is like the NE-2 externally but has a third electrode intermediate "trigger" electrode between the power electrodes.
The trigger electrode triggers the plasma by ...
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My DIY tube amplifier distorts more than I planned
I have built a JTM145 clone. The original amplifier is clean and distorts when the volume is turned up, but my own copy of that amplifier distorts at low volume at the second 12AX7 tube from pin 7 to ...
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Help understanding the control circuit of a gas discharge tube
I'm trying to interpret exactly how you get this famous IxU curve of a gas discharge tube you can find on several places, including the Wikipedia page about electric discharge.
Image - Original work: ...
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Tube preamp overdrive question
Is it possible to add an overdrive gain pot (instead of just simply a bypass switch) to a preamp tube circuit?
I am designing a new amplifier, and I want to include an overdrive/distortion option to ...
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RF power amplifier tuning of output stage tube vs transistor
In the old days with vacuum tubes for power amplifiers we carefully tuned the output stage, dipped the plate current to get maximum efficiency.
Looking at todays transistor PA circuits I don't see a ...
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Required transformer voltage for voltage regulator tubes in series
First of all some small context: I am attempting to design and build a clock with old electricial components, without silicon components. This question is about the power supply circuit. Note that I ...
user326520
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Is it possible to add a potentiometer instead of a fixed resistor to control negative feedback?
Here you see the circuit of my tube amplifier. Is it possible to replace the resistor with a 250k potentiometer to control the negative feedback, or can it cause some other problems?
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How does the feedback in this tube amp output driver work?
The figure shows the output stage of a vacuum-tube audio amplifier. While I was reading through this schematic, I noticed there is a some kind of feedback associated with R24. However, this feedback ...
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Voltage output on thyratron gas tube relaxation oscillator VCO?
I know that thyratron gas tubes can be used to make a sawtooth like relaxation oscillator:
My question is for a modification of this same circuit that makes it act like a voltage controlled ...
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Why is a pentode tube more power efficient than a triode tube?
As title.
I read some article and it says something like this:
Tetrode was invented to reduce grid-plate capacitance.
Pentode was invented to reduce secondary emission.
I also heard that a pentode ...
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Looking for Power Transformer for ECC99 OTL Headphone Amp
I'm planning on building an OTL headphone amp using a pair of ecc99 (I got matched pair of soviet 6n6p in my hand). Eliminating output transformer would reduce the complexity of the circuit and the ...
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What is secondary peak to peak of 290BEX transformer if primary pp is 325V and turns ratio 1:2.95?
I want to be absolutely sure of this because it is the first crucial part of my LTSpice Fender 5e3 simulation. Currently I have this .subckt(with comments):
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I have a carvin v3m 50watt tube amp head, red plating/bias help
The amp has 4 el84 tubes and 4 12ax7 pre amp tubes, the amp lost about half of its volume and the power tubes are red plating, is there any thing other than the tubes that I should be looking out for ...
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How to match harmonica impedance to a tube amp to eliminate feedback
What circuits eliminate feedback between hi z harmonica mics and high gain guitar tube amps?
Do FET circuits work? I have used tube bases attenuators in the past for 50 watt amps, but they reduce the ...
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Are fluorescent tubes dangerous?
I'm disassembling a Sega GameGear.
The capacitors inside are all rated 50v or lower, so it shouldn't be hazardous in that regard (I will discharge them anyway just to be sure).
However, the metal ...
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need for decoupling capacitor in a Fender Bassman
why is there no need for a decoupling capacitor in the second preamp stage (highlighted section)?
I would imagine a 0.02-400V capacitor just before the grid of the second half of the valve to block ...
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Gas discharge tube load type
I can not find any information about the type of load of neon lamps, for example neon probe or wall contact plug or extension cord with switch with small red lamp. I think this is a passive capacitive ...
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Short circuit in Peavey Valve King VK212
This is a follow up question from:
Guitar amplifier repair: burnt fuse, capacitor, what else?
I continue to work on the same case. In another module I've found a short to ground where the red dot is:
...
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Replacing selenium rectifier diode with silicon 1N4007
I want to replace this selenium diode on an old tube amplifier with a silicon equivalent. Normally, this diode would have a lower value resistor in series with it such as a 15 ohm. Instead, this one ...
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Photo-multiplier Tube Pin Configuration
Pin configuration of a photo-multiplier tube (PMT) is presented in its manual as can be seen in the attached image. All dynodes have been related to specified pins (numbered circles in the image) ...
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Biasing network for phototubes and photomultipliers
I have some doubts about typical biasing network for vacuum phototubes and photomultipliers.
Precisely, let's start by a simple photocathode.
I have seen some biasing network like this one:
In this ...
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Why is there a winding on a capacitor?
I just came across this tube RIAA preamp on which there is a coil on the input capacitor, can someone please explain what's the reason of such thing? The schematic and the actual circuit bellow.
The ...
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Obtaining 4-4.2V rail from 5V output of LM7805 voltage regulator
I'm creating a numitron clock with 4xIV-9 tubes (seven-segment filament displays) and have decided to illuminate them using shift registers controlled by an arduino. Each segment takes a voltage of 4-...
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Are these UV-C tubes meant to be run only on pure AC ballast?
I’ve this portable small T5 4W UV-A 300-400nm black light tube lamp with me. I’m trying to see if it’s possible to use a 4W UV-C lamp in the same fixture. But I noticed that the lamp has the violet ...
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Fuzzy digits when driving with TPIC6B595
I designed a schematic and PCB of a simple Nixie clock and I hope that someone will be able to explain what's happening.
The problem is that when I'm driving the cathodes with TPIC6B595 shift ...
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12AX7 Valve Overdrive/Distortion Effect Pedal
I'm following the schematic below using the recommendations plus a couple of extra LEDs. With the footswitch in the enabled position, I'm not getting any sound. In the bypass position, the input and ...
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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.
...
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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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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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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 '...
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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 ...
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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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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, ...
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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 ...
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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 ...
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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 ...
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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?
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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-...
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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,...
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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 ...
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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 ...
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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 ...
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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 ...
user41067