Questions tagged [vacuum-tube]
Any device that incorporates an evacuated chamber in which free-floating electrons are manipulated.
157
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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
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4answers
2k 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 ...
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1answer
264 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 new format.
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3answers
122 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
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2answers
109 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
...
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1answer
39 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 ...
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1answer
96 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....
5
votes
2answers
210 views
Troubleshooting Hum in a Tube Guitar Amp- Resolved!
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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1answer
205 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 ...
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2answers
86 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 ...
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2answers
105 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 ...
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1answer
153 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-...
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3answers
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 ...
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1answer
76 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 ...
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1answer
97 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 ...
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1answer
174 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
464 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 ...
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1answer
73 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 ...
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2answers
219 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
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2answers
70 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. ...
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1answer
291 views
Little Bear T11 tube phono pre-amp VACUUM TUBE upgrading
I have a Little Bear T11 vacuum tube phonograph pre-amp. It has three
Shuguang 6N2-J "Military Grade" vacuum tubes which I want to upgrade. The pre-amp also has a Chinese made 6z4-J Rectifier. The amp ...
3
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3answers
223 views
Coloured coating within CRT
I have noticed that a lot of CRTs have a coloured coating inside of them that would appear to have practical purpose other than maybe protecting the aquadag. Paints and plastics tend to be avoided in ...
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3answers
157 views
Vacuum tube stereo amplifiers with an odd number of tubes
While researching the world of vacuum tube audio amps, I noticed that many commercially available stereo amps have an odd number of tubes. Here's a random example.
How can a decoupled stereo sound be ...
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1answer
218 views
Power transformer question in vacuum tube circuit
I am having trouble wrapping my brain around this power transformer circuit. I must be missing something very fundamental, so I apologize in advance for that.
Can someone explain to me why the center ...
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0answers
135 views
Vacuum tube voltage regulator - capacitor on the output
I'm thinking about building a tube-based voltage regulator to provide the power for the screen grids of the output tubes.
I have seen multiple designs of this and am currently thinking of doing it ...
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2answers
100 views
Diode on op-amp output to drive tube
I am working on a tube based guitar amplifier, and found an interesting schematic online. There is an op-amp that has diodes across a resistor in the feedback path.
I understand what it makes the op-...
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2answers
216 views
Modify a 1629 magic eye tube circuit to a 6E5S tube?
I've an EICO 950B capacitance tester with me. It has an aging 1629 magic eye tube. I have a bunch of 6E5S tube with me. Can you guys guide me with the modification?
I know the first step to this is ...
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3answers
185 views
Why do tube amplifiers have such (relatively) small reservior capacitors?
In learning about guitar amps, I've been studying the schematics for solid state and tube amplifiers, and I found a pattern that I've never seen an explanation for.
If you consider any of the main ...
13
votes
4answers
2k views
Why put a step-down transformer after a vacuum tube in an a valve amplifier?
I'm researching valve amplifiers. I found this schematic for one:
So the input is amplified by the first valve, and then the amplified signal is amplified again by the second valve, right?
My ...
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0answers
160 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 ...
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1answer
128 views
Is it normal for the OC2 vacuum tubes to glow bright orange during operation & OA2 to flicker while running?
I just got this vintage Heathkit IO-10 oscilloscope from ebay. Just tried powering it up and it seems to be working fine. But I noticed that the OC2 tube seems to glow very bright orange and the OA2 ...
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2answers
340 views
Question on Use of Y2 Saftey Capacitor in AA5 Style Tube Radio
In a radio I am restoring, there is a 0.1 uF capacitor between B- and chassis, designated as C12. My thought process is that if this capacitor were to fail, I would not want B- shorted to chassis as ...
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4answers
1k views
valve tone control circuit build
Here I have built the following schematic but have encountered some problems. The treble was crackling and the bass was dropping out. I have somewhat fixed the treble issue with grounding the pots but ...
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2answers
317 views
Calculating current in an unknown transformer with multiple isolated secondaries
I have an old power transformer that I'm retrofitting into a new valve amplifier. Having measured the voltages on the secondaries when 230V is applied to the primary and got the following results:
P: ...
3
votes
1answer
229 views
Amplify Raspberry Pi Zero W Audio with 60s Tube amplifier circuit
First of all, thank you for taking a look at my question.
Electronics is not my field of expertise, and I have found myself a bit stuck.
I have been restoring some old 50s and 60s tube amplified ...
0
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1answer
54 views
Calculating voltage, current, and impedance values on an old transformer
I'm working on an old valve amplifier, with the intention of reusing the transformers in a new project. I've used what I know of transformers to calculate the ratio of each winding the corresponding ...
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0answers
271 views
What is happening to this vacuum tube?
I’m trying to repair a 63 year old record player. Opening it up, all of the electronics have aged badly, except for the drive motor, which is basic enough that it operates properly. I know enough ...
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4answers
158 views
Help me trying to understand transistor and vacuum tubes? [closed]
Obviously I'm a newbie in electronics and I think I understood how transistors and previously, vacuum tubes work (as a electrical switch, I'm disregarding amplifying in this question).
But for me is ...
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1answer
337 views
Tube power supply capacitors replacement
I'm building the following power supply (credits to Audio design guide):
I would like to replace C5, C8 and C9 with 1000uF capacitors (with the same voltage rate). From my understanding these ...
4
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1answer
330 views
Need help reading a schematic, is this a 220k log b pot?
This is saying a 220k log b potentiometer for the tone pot VR8, correct? That is such an extremely odd value, but I don't see that sort of notation very often either and I wanted to make sure I'm not ...
6
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3answers
703 views
Which particular transistor types represent triode and pentode vacuum tubes best?
If you encounter an old text which uses tubes instead of transistors, and if you are not familiar with the tubes, which one of the transistor from the following transistor tree would you think of to ...
3
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2answers
472 views
MAX6966 a suitable sink driver for nixie tubes?
I recieved some IN-14 nixie tubes for Christmas, and was hoping to implement them in a project i have been considering for some time. The details are unimportant, except that each nixie tube should ...
6
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2answers
1k views
Tube cathode biasing with CCS
I'm unable to understand how the biasing of the 12AX7 Tube in the schematic below works.
In particular, I can't understand how the LM334 can switch on, where does it find the required voltage to ...
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1answer
332 views
Method for inductance measurement of iron core vacuum tube audio output transformers
I am involved in the direct measurement of inductance of vacuum tube audio output transformers. Inductance levels vary from around 1 H to 50 H for the primary and down to just a few mH on the ...
0
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1answer
139 views
What type of resistor component is this?
I have an RCA Victor 35x tube radio and I need to know what type of resistor this is and what it's purpose is?
There is some wire wrapped around the resistor and it's attached to the antenna.
...
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2answers
1k views
What do “cycles” in a capacitor mean?
I'm trying to replace some old leaky capacitors for this radio I'm working on and in the data sheet they have this rating of cycles for the large capacitors near the bottom of the sheet here:
What ...
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2answers
247 views
Edison effect in vacuum
I was reading this page which says:
What Edison discovered (and it was promptly dubbed the "Edison
effect") was that electrical current doesn't need a wire to move
through. It can travel right ...
5
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3answers
1k views
How to identifiy this “2222 063 90025” vintage capacitor?
I am restoring an old stereo valve amp and would like to test (and replace if needed) some components. I don't know the history of the amp, but it's made in New Zealand and looks to be from the 1960'...
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1answer
172 views
Can a vacuum tube Triode increase the voltage in a circuit above the voltage rating of the batteries in the circuit?
I guess this will take a little explanation. I have not mastered the "sketching" used on this website yet. The triode in question has one plate circuit connected to a 90 volt battery and the filament ...
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2answers
76 views
Can an audion tube amplify a pulsating direct current or must the current be converted first to an alternating current? [closed]
Can an audion tube use a pulsating direct current as input and magnify the signal from the electrons flowing from the filament without first converting it to AC current? The reason I ask is that :
I ...
