Questions tagged [vacuum-tube]

Any device that incorporates an evacuated chamber in which free-floating electrons are manipulated.

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18
votes
5answers
2k views

Why is this meter giving different readings depending on its orientation?

My newly-restored (re-capped) 1950s vacuum tube voltmeter is now operational...but there's one further issue. The meter gives correct readings when lying on its back, but when oriented vertically- as ...
0
votes
0answers
80 views

600V DC Switch method question

I am making a linear PSU capable of O/P 600v @ 300mA. This is for vacuum tube experiments. I need to connect/disconnect the load from the PSU using a switch. I will not turn OFF the PSU itself. I ...
0
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0answers
55 views

Designing a hybrid RF ampilifier with tube and transistors

I have an 807 vacuum tube and I want to design a RF power amplifier with it. Since I have only one tube so I want to use transistors for the rest of the power amplifier circuit. The 807 tube will be ...
0
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1answer
74 views

Strange ringing/oscillation in guitar tube amp

So I finally finished building my guitar amp. It sounds great, except for one thing that occurs when gain is too high. What happens is that when I turn one of the preamp volume pots high enough ...
0
votes
1answer
169 views

Restoration/mod of mid-1960s PP 2xEl844 4x6AT6 guitar amp, voltage, hum problems. Similar to Fender 5F10 schematic

Is this the right place to find solutions to the above problems? I'm trying to make this amp usable, but after some rebuilding and reconfiguring, I still have a hum problem and what seems to be odd ...
0
votes
0answers
40 views

Drive an older VFD tube via an Arduino et. al

I have a beautiful old itron DP95A4 tube that I would like to use as a small display to visualize some data. I suppose I'd need a driver and some sort of multiplexer, preferably used with an Arduino ...
1
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2answers
90 views

Vacuum tube DC amplifier circuit

I am currently working on a project to amplify a very small signal (about 10 millivolts) using a vacuum tube. I understand vacuum tubes were used as amplifiers and transistors back in the day, but I ...
2
votes
0answers
38 views

Vacuum tube emission (anode current, transconductance) percentage that is considered GOOD

Russian vacuum tube datasheets almost always specifies anode current like Ia = 100 mA +/-20mA at some conditions. The same with transconductance. But western tube datasheets specifies only one ...
2
votes
1answer
77 views

Tube amplifier preamplifier

I received this little two tube preamp http://www.gikfun.com/electronic-diy-kits-c-7/6j1-tube-preamplifier-board-20-stereo-multiple-diy-kit-p-730.html It comes with 9 470uF caps. The symbol on the ...
3
votes
1answer
205 views

Can you cover tubes?

All of the tube amp designs i see have the tubes exposed to air. Is this a design feature for heat dissipation or is it simply because some find it pretty?
2
votes
1answer
152 views

Powering 6E1P vacuum tube VU meter

This will probably be a rather lengthy and detailed question(s). I wanted to break things up, but since everything is kind of related, I've decided to keep it as one post. I do apologize if that's not ...
-2
votes
1answer
97 views

Replacing X-ray or any radiation generating vacuum tubes with solid-state alternatives? [duplicate]

What are the reasons X-ray vacuum tubes could not be replaced by solid state alternatives? I'm thinking if it is possible to make a compact solid-state X-ray or higher energy photons generator just ...
2
votes
1answer
68 views

Which ground plane shape is more appropriate in my application?

I've been working on re-making the two PCBs in the HP 211A square-wave generator from 1955, as the traces on the one I own are starting to peel off. Focusing on one board, the multivibrator, for the ...
3
votes
5answers
763 views

Can a lower voltage overheat a magnetron?

Background I am working on a microwave oven that starts to emit an odor after 2 minutes of full heating despite otherwise working correctly. The smell is the same as that "sweet", ...
0
votes
2answers
100 views

Why does triode voltage drop change as a function of grid voltage?

Imagine a thermionic diode connected in series with a resistor \$R\$. The circuit is hooked up to a voltage source \$V\$. The diode conducts a certain current \$I\$ and \$\Delta V_\text{diode}\ + \...
1
vote
1answer
134 views

What Causes Voltage Drop In A Vacuum Tube Diode

This question is about the voltage drop across a vacuum tube diode. Consider a circuit that consists of a battery, a vacuum tube diode, and a resistor all wired in series. My understanding is that, at ...
2
votes
3answers
222 views

Why most particle accelerators used vacuum diodes instead of transistors?

HERMES III (High Energy Radiaton Megavolt Electron Source) at the Sandia at Sandia National Laboratories is the world's most powerful gamma ray generator. HERMES-III produces a highly energetic beam ...
5
votes
3answers
194 views

Amplifiers without vacuum tubes or transistors?

Are there amplifiers that can work without vacuum tubes or transistors? Is it possible to create a working amp with high power without vacuum tubes or transistors?
0
votes
1answer
59 views

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) ...
2
votes
2answers
42 views

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 ...
1
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0answers
94 views

Guitar Amp Power Supply Issues

I have a B-52 AT100 guitar amp on my bench (naturally, it wouldn't let me attach the .pdf I have of the schematic, so I had to attach it as two .jpegs. The schematic can easily be found online though, ...
14
votes
1answer
295 views

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 ...
4
votes
1answer
2k views

Insane power dissipation on EL34 tubes in push-pull power stage

Here's my circuit: (now without voltages) It uses two EL34s biased to -30V (fixed bias). Here's the loadline (made with this calculator): When no signal is applied voltage on EL34 anodes is 360V, as ...
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0answers
33 views

How to detect if vacuum tube is overdriven?

I want to somehow indicate(with LED diode for example) to user when vacuum tube is overdriven (When grid voltage is greater or equal than cathode voltage). My first idea was to connect a LED diode ...
1
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3answers
173 views

Plate current use of 12Ax7 vacuum tube at low voltage

Does anyone know the current used by at 12Ax7 (or similar) vacuum tube when in normal (triode) operation using a plate voltage no more than 10VDC? I'm not considering the heater current (~300mA at 6....
0
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1answer
166 views

Headroom of cathodyne phase inverter (in vacuum tube amplifier)

I know that gain of cathodyne is almost 1, so if it's going to produce 12V peak output, it has to take 12V peak input. However, if the bias is set to something like (-)1-1.5V, then peak voltage of ...
5
votes
4answers
2k views

In a parallel plate capacitor, how does placing a metal in between the plates reduce the capacitance?

This source claims that putting a metal plate in between the capacitor plates greatly reduces the capacitance. How is this possible? Two equal capacitances in series decreases the capacitance by ...
2
votes
3answers
218 views

Lighting up old vacuum tubes and making them turn on/off

I know there were older posts about lighting up old vacuum tubes but I would also like to turn them on and off. I am a complete newbie with no real electronic experience here so please bear with me. ...
5
votes
2answers
359 views

Low power tube headphone amplifier design

I have never worked or even listened to tubes/valves before, so its about time I did. I wanted a simple design to work with being my first tube project, and have found this from diyaudioprojects.com: ...
1
vote
0answers
88 views

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 ...
0
votes
0answers
264 views

How close can an output transformer be to a preamp tube?

Imagine a layout for a tube amplifier. The power transformer is on one side, and the output transformer, input jack, and preamp tubes are on the other side. (Take a look at the Soldano SLO for example)...
3
votes
4answers
3k views

Measuring voltage across 1 ohm resistor

This might be a very stupid question, but I can't seem to figure this out and I'm going nuts thinking about it. Assuming you are trying to adjust the fixed bias of a tetrode push pull pair in a tube ...
1
vote
1answer
356 views

Is there a chart that translates old tube symbol to the new tube symbol [closed]

Im looking for a chart that helps you translates the old tube symbol into the updated format.
1
vote
6answers
436 views

Magnetron Working Principle

I was reading this simple description of magnetron working principle. Can you explain me why when electrons go near the cavities, they start to resonate at microwave frequency? I do not see the link ...
3
votes
2answers
206 views

Fixing an old radio [closed]

I am trying to fix an old radio that my girlfriend just bought. It's from around 1964. I'm just a normal electrician and I am not used to fixing things like this. Radio model: Huldra 7-45 Skapmodell ...
0
votes
1answer
70 views

Calculating Capacitance / Rolloff Frequency for Across the Line RFI Supression

I’m in the process of restoring my first All American Five (AA5) tube radio – in this case, a GE Model 115 from the late 1940s. As I’m getting ready to order replacement capacitors for it, one of ...
0
votes
1answer
236 views

Heating vacuum tube filament via capacitor

As I understand vacuum tubes (like triode / pentode) usually are designed to be heated with certain current through the filament. And usually it is about low-voltage and comparatively high-current. E....
6
votes
2answers
571 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. ...
2
votes
2answers
910 views

Tube Transmitter Issues

I'm back working on my friend's 807 tube transmitter. I've had some previous posts on this and I'd like to thank all the people who responded for your help! I bought an oscilloscope and a dummy load ...
0
votes
2answers
177 views

Electrodes and number of pins in vacuum tubes

I am confused regarding the terminology 'diodes', 'triodes' etc and the number of pins in these elements. If a diode has a cathode, an anode, and a supplementary anode (the control grid or plate) and ...
-1
votes
2answers
112 views

How to obtain 360vdc from 240vac for audio use without a transformer?

I'm in the process of creating a tube guitar amplifier with an output power of ~6w (fender vibrochamp AA764) which requires the use of 360-400vdc. How could I obtain such a voltage from mains without ...
1
vote
1answer
253 views

Why would a tube radio leave the 6.3V heater tap on the transformer disconnected?

I'm attempting to repair a Clarion C104 tube radio. I started the repair years ago, put it away, and now I'm giving it another attempt. When I started the repair, the transformer (Clarion part no. C80-...
10
votes
4answers
2k views

In a vacuum triode, what prevents the grid from acting as another anode?

A triode vacuum tube has three electrodes, namely an anode, a cathode and a control grid in between of those. Assuming that the filament is hot, current would readily flow from the cathode into the ...
0
votes
1answer
96 views

+/- 96 V transformer less power supply design

I know this is a dangerous practice, but obtaining a transformer to make a vacuum tube power supply in my country is prohibitively expensive. So i have to go for transformer less psu. I am just making ...
1
vote
1answer
406 views

tube amp - high power supply voltage ?! troubleshooting

So I started working with troubleshooting a channel imbalance on the schematic attached, 12ax7 + 6L6GC push pull. But the problem seems to be a bit different... My voltages seem to be a bit hot!! (a ...
0
votes
1answer
467 views

Triode Regenerative Receiver Circuit - room for improvement and possible errors

I've designed this radio circuit, it's made to work on the 80m and maybe 40m band. Regen is controlled using a pot in the tickler coil. Tube is ECF82, coil is air cored on a 30mm former. Will it be ...
6
votes
2answers
1k views

Tube transmitter tuning

I am trying to tune/tweak/repair this transmitter for a friend of mine. It is oscillating, and it has rf power on the antenna, but it just doesn't seem as "strong" as it should be. The diagram says ...
0
votes
1answer
120 views

Tube transmitter plate current meter question

Can I install the mA meter in this schematic directly in the circuit? This is the high voltage plate supply and there is RF on it. The diagram doesn't specify if there is any circuitry to adapt the ...
0
votes
2answers
405 views

3.5 MHz 2W AM vaccum tube transmitter [closed]

What do you think of my 80m band radio transmitter I designed? Originally I though about using an Armstrong oscillator, due to its simplicity and sine wavyness, but I heard that crystals are better, ...
0
votes
2answers
100 views

Phase splitters/inverters using valves with directly-heated cathodes

I'm building an audio amplifier using Raytheon 6418 valves and I'm struggling with the phase splitter. The 6418 has a directly-heated cathode and I'm wondering what limitations this might introduce. ...