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A simple workshop generator m.cz.

żarówka rtęciowa 14730 37

TL;DR

  • A homemade workshop sine-wave generator provides 100 Hz, 1 kHz, and 10 kHz outputs for servicing amplifiers and receivers.
  • It uses a Wien bridge oscillator with a dual TL082 op-amp, a 60V/20mA telephone bulb for amplitude stabilization, and a buffer stage.
  • The power supply runs from 230 V mains, uses a TS2/14 transformer with a Delon doubler, and delivers about 14 V DC plus 11 V AC.
  • The output level is adjustable from zero to about 4 Vrms, and the project cost only a dozen zlotys.
  • Recycled materials kept the price low, but missing parts stretched the build to about one year.
Summary generated by AI based on the discussion content.
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  • A simple workshop generator m.cz.

    Hello,

    Necessity is the mother of invention, sometimes the right equipment is needed for servicing, such as a low-frequency signal generator used to repair amplifiers and receivers. There are a lot of devices on the market, both new and used, but their price is unacceptable to me. So I thought that in order to save costs I would build something like this. The choice fell on a simple sine wave generator with three frequencies: 100 Hz, 1 kHz and 10 kHz, powered from the 230 V mains. I found a description of the electronic circuit on the Internet. It comes from the popular magazine Elektronika Praktyczna 1/95.

    The mechanical construction consists of a base made of steel sheet with two sides riveted to it. The lid is also cut from the same material. The metal pieces were cut with a hacksaw and then bent with a vice in my dad's garage. On it, the power supply is screwed with M3 screws through distance sleeves a few millimeters long. The front panel is made of plastic. On the latter, the so-called a small chassis with a generator board, a dependent isostat switch with frequency selection RC elements, a control lamp and a BNC output socket. The inscriptions were made with a thin waterproof marker. Before final assembly, the steel parts were painted with anti-corrosion paint. The box is permanently connected to the PE conductor of the power cable.

    The modules on the boards are connected by thin wires. The power supply includes a TS2/14 domestically produced transformer and a rectifier with a Delon doubler equipped with two filtering capacitors. From it comes the DC voltage of approx. 14 V and the alternating voltage of approx. 11 V to power the control lamp with the telephone bulb. The boards were etched in a solution of sodium persulfate heated indirectly by solar energy, the process for the power supply circuit took about 40 minutes. The Wien bridge generator contains a double TL082 operational amplifier placed in a socket. The first stage produces a sinusoidal signal with the selected frequency, the second is a buffer. A 60V/20mA telephone bulb is used to stabilize the amplitude, and the Telpod CN-15 cermet potentiometer is used to set it. The signal is regulated by a Telpod SP 1.2 carbon potentiometer from zero to approx. 4 Vrms. On the back there is an output ground switch.

    The approximate cost is a dozen zlotys and is low due to the use of recycled materials and parts, e.g. a three-core power cord with a plug is made of electronic scrap, the casing sheet was purchased at a local scrap yard, and the plastic is recycled. The rest of the used parts I had from my own stock. The elements that I bought myself are a mains transformer in a stationary store, two electrolytic capacitors (TME) low-SR Panasonic 470 uF/25 V/105 °C and a double operational amplifier TL082 (Allegro). Due to the shortage of some parts, work on this device took about one year.

    I add some photos of the project:

    A simple workshop generator m.cz.
    A simple workshop generator m.cz. A simple workshop generator m.cz.
    A simple workshop generator m.cz. A simple workshop generator m.cz. A simple workshop generator m.cz. A simple workshop generator m.cz.

    Cool? Ranking DIY
    About Author
    żarówka rtęciowa
    Level 38  
    Offline 
    żarówka rtęciowa wrote 3912 posts with rating 393, helped 364 times. Live in city Pelplin. Been with us since 2005 year.
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  • #2 20641570
    CosteC
    Level 39  
    Posts: 5336
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    Rate: 1652
    żarówka rtęciowa wrote:
    On the back there is an output ground switch.

    The switch is visible in some photos, and in others it is not. BNC is also ordinary, not isolated, so it is at PE potential - the same as in most function generators. So what does this "output ground switch" do?
  • #3 20641606
    żarówka rtęciowa
    Level 38  
    Posts: 3912
    Help: 364
    Rate: 393
    Hello,

    CosteC wrote:
    The switch is visible in some photos, and in others it is not visible. BNC is also ordinary, not isolated, so it is at PE potential - the same as in most function generators. So what does this "output ground switch" do?

    The switch is designed to break the ground loop when the output ground of the generator is connected with the tested circuit and the analog oscilloscope, in which its input socket is is permanent connected to the PE (protective) conductor. The photos were taken at different times.
  • #4 20641609
    CosteC
    Level 39  
    Posts: 5336
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    żarówka rtęciowa wrote:
    The switch is designed to break the ground loop when the output ground of the generator is connected with the tested system and an analog oscilloscope, in which its input socket is permanently connected to the PE (protective) conductor. The photos were taken at different times.

    Can you make some diagram because I don't understand. I have, perhaps mistakenly, the impression that the ground loop break is in the wrong place.
  • #5 20641631
    Mateusz_konstruktor
    Level 37  
    Posts: 4265
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    żarówka rtęciowa wrote:
    The box is permanently connected to the PE conductor of the power cable.

    And what about the mains fuse?
  • #6 20641704
    żarówka rtęciowa
    Level 38  
    Posts: 3912
    Help: 364
    Rate: 393
    Hello,

    Factory-made Polish devices with these transformers, e.g. power supplies for radio receivers or emergency lighting modules. they have no mains fuses on the mains supply side. So there is no need to use them in my design.

    As for the ground switch, I will soon draw and post a diagram.
  • #7 20641728
    CosteC
    Level 39  
    Posts: 5336
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    Rate: 1652
    żarówka rtęciowa wrote:
    Factory-made Polish devices with these transformers, e.g. power supplies for radio receivers or emergency lighting modules, do not have mains fuses on the mains supply side.

    And what happens if the transformer gets a short circuit of, say, 200 ohms and starts to heat up to the point where it can ignite?

    I still don't understand what the switch does. Can you make a drawing?
  • #8 20642016
    prosiak_wej
    Level 39  
    Posts: 5273
    Help: 501
    Rate: 1459
    CosteC wrote:
    I still don't understand what the switch does.


    I believe it cuts the PE wire from the mains cord from the housing.
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  • #9 20642020
    pawlik118
    Level 34  
    Posts: 2425
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    Rate: 608
    CosteC wrote:
    BNC is also ordinary, not isolated, so it is at PE potential - the same as in most function generators.

    The front panel is made of plastic - it is non-conductive.

    Added after 1 [minutes]:

    I like. A reasonably maintained compromise of aesthetics to the amount of work.
    It is neat and looks decent.

    From what I remember, the fuse at the transformers, up to ~2.5VA, is not required. Perhaps this is due to the fact that the very thin wire of the primary winding is not able to carry the current that would give off power that could burn the insulation between the primary and secondary sides.
    e.g. Breve on their products
    gives the fuse value https://www.tme.eu/pl/details/tez6_d_6v/transformatory-do-pcb/breve-tufvassons/tez6-d230-6v/
    Does NOT provide fuse value https://www.tme.eu/pl/details/tez2.5_d_10.510...e-tufvassons/tez2-5-d230-10-5-10-5v/?brutto=1¤cy=PLN&gclid=EAIaIQobChMIi5eS0dD1_wIV5AuiAx0 VSwghEAQYAiABEgIZSPD_BwE
  • #10 20642060
    CosteC
    Level 39  
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    pawlik118 wrote:
    From what I remember, the fuse at the transformers, up to ~2.5VA, is not required. Perhaps this is due to the fact that the very thin wire of the primary winding is not able to carry the current that would give off power that could burn the insulation between the primary and secondary sides.
    e.g. Breve on their products

    I don't know such a recipe... It would be very strange, besides it assumes that there will be no magical failure anywhere else in the device that could lead to a fire..
    The fuse has two roles - protection against fire and protection against electric shock, of which it protects against electric shock only in specific cases - because depending on the position of the plug, the fuse can be on the neutral line.
    pawlik118 wrote:
    The front panel is made of plastic - it is non-conductive.

    I don't see it, the author can confirm/deny. I think it's October...
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  • #11 20642138
    123104
    Level 12  
    Posts: 22
    Rate: 17
    The author wrote: "The front panel is made of plastic."
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  • #12 20642153
    CosteC
    Level 39  
    Posts: 5336
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    Rate: 1652
    123104 wrote:
    The author wrote: "The front panel is made of plastic."

    I'm honored, yes. I missed it.

    Still somehow I feel bad without a fuse ... Indeed, a wire in a tiny power transformer should not fall out of the transformer and strongly limits the current ... But could not a short circuit inside the primary winding heat it up too much? Modern transformers often have a thermal overload fuse for this purpose.
  • #13 20642162
    pawlik118
    Level 34  
    Posts: 2425
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    Rate: 608
    I'd probably give a fuse, just to feel good. Some time ago, an older colleague, a designer, told me about the "lack of its requirement" in small transformers, and it concerned certified medical equipment (2VA transformer). It sounded convincing then. It would be worth checking, for example in Breve :)
  • #14 20642314
    acctr
    Level 39  
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    żarówka rtęciowa wrote:
    60V 20mA telephone bulb is used to stabilize the amplitude,

    Why this tension? Have you checked its characteristics for voltages equal to the amplitude present in the generator system?

    Moderated By Mirek Z.:

    Don't lower the level of the forum! You really don't need to write redundant posts.

    Helpful post? Buy me a coffee.
  • #15 20642317
    prosiak_wej
    Level 39  
    Posts: 5273
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    pawlik118 wrote:
    The front panel is made of plastic - it is non-conductive.


    A board made of foamed PVC?

    As for the fuse - recently I have been resuscitating Carel controllers from Liebherr MediLine freezers. The controllers have a converter, which is an independent module on four legs. There is no fuse in the controller itself, I don't know about the converter - it is flooded with resin. I got one driver that got flooded from the outside. The plate was fried until the protection in... the laboratory's installation worked. Also, even if the converter had its own fuse - it would be of no use, because the manufacturer of the controller did not give anything.
  • #16 20642541
    ^ToM^
    Level 42  
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    Nice product.
    I made such products myself somewhere in the 80s, following the example of Maria and Wojciech Nowakowski's systems. All the devices presented in their books were built by them and worked almost from the first switching on.
  • #17 20642544
    pawlik118
    Level 34  
    Posts: 2425
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    Rate: 608
    prosiak_wej wrote:
    A board made of foamed PVC?

    I do not know, there is info in the description, only that it is a material. Is PVC still an insulator?
  • #18 20642550
    ^ToM^
    Level 42  
    Posts: 9051
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    acctr wrote:
    żarówka rtęciowa wrote:
    60V 20mA telephone bulb is used to stabilize the amplitude,

    Why this tension? Have you checked its characteristics for voltages equal to the amplitude present in the generator system?


    The bulb is correct because the key parameter is its current, not voltage. Use a light bulb with as little current as possible. Its non-linearity is used for stabilization. This solution was used even in professional constructions.

    Here, Mr. Piotr Górecki described it more easily and I recommend an interesting reading of the PKE episode:

    pke14.pdf (1.68 MB)You must be logged in to download this attachment.
  • #19 20642590
    szeryf3
    Level 30  
    Posts: 2046
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    Cool, useful, cheap DIY. Well, and from the goodies.
    I know that the transformer should have thermal protection, but I would put a fuse. Just for my peace of mind. What you will do is up to you to decide.
  • #20 20642995
    pikarel
    Level 39  
    Posts: 5015
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    Rate: 1838
    The generator is the basis in the electronics studio for testing acoustic devices, and the circuit from the subject has an almost immeasurable value of distortion.

    Foamed PVC is a grateful material for front panels in all DIY; it requires only a knife with a sharp tip for cutting to size and scissors for making holes.
    The switch - is a substitute for what is offered in D-Boxes, i.e. you can disconnect the mass of the system from the ground. A plus from me.

    Now from a different barrel :)
    Who saw a mains fuse in the antenna power supply for the "grid"? - hand up.
    I do not see.
    Who has seen what a damaged transformer 2/XX looks like with the primary winding broken due to overheating?
    Anyone who has seen it knows that no such transformer had a breakdown between the windings, because the windings are not wound on each other, with insulating spacers - but side by side, on a carcass with appropriate insulation (from an injection molding machine).

    I - for example - put on a winter hat and gloves when I open the freezer, because I "believe" that the freezing temperature in it can freeze my ears and hands. Why am I doing this?
    Because the temperature of -20 ° C has frostbite many people's ears and hands, so I prefer to protect myself, and the fact that I look and act like an idiot - it's a little Pikuś.
    :)
  • #21 20643094
    pawlik118
    Level 34  
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    I saw a damaged Breve 2VA 9A transformer. A break in the primary winding, slightly swollen filler from the bottom.
  • #22 20646215
    yogi009
    Level 43  
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    żarówka rtęciowa wrote:
    As for the ground switch, I will soon draw and post a diagram.


    That's where I would start the topic. These photos don't say much about the project, and not everyone has an archival RE number on their shelf.
  • #23 20647191
    żarówka rtęciowa
    Level 38  
    Posts: 3912
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    Rate: 393
    Hello

    I've attached a diagram to clear your doubts.

    A simple workshop generator m.cz.

    prosiak_wej wrote:
    pawlik118 wrote:
    The front panel is made of plastic - it is non-conductive.

    A board made of foamed PVC?


    It is ordinary ABS plastic.
  • #24 20648352
    yogi009
    Level 43  
    Posts: 14697
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    żarówka rtęciowa wrote:
    I've attached a diagram to clear your doubts.


    A friend mocks, is the weekend difficult? is this a schematic?
  • #25 20648458
    ^ToM^
    Level 42  
    Posts: 9051
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    Rate: 2935
    yogi009 wrote:
    żarówka rtęciowa wrote:
    I've attached a diagram to clear your doubts.


    A friend mocks, is the weekend difficult? is this a schematic?


    Why. This is also a diagram, but rather a block diagram.

    Added after 12 [minutes]:

    yogi009 wrote:
    żarówka rtęciowa wrote:
    As for the ground switch, I will soon draw and post a diagram.


    That's where I would start the topic. These photos don't say much about the project, and not everyone has an archival RE number on their shelf.


    Not RE but EP and everyone has access, just go to:

    https://ep.com.pl/archiwum/1995/13113-jan-1995

    Description of the device in the attachment here:
    Generator ...oryjny.pdf (1018.42 kB)You must be logged in to download this attachment.
  • #26 20648594
    yogi009
    Level 43  
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    So just paste the link. Looking at the application itself, however, I would opt for the ICL8038 (or its newer variants). Three waveforms, larger range, little layout complication. And five adjustments (even offset).
  • #27 20650848
    Gismot
    Level 19  
    Posts: 282
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    Rate: 170
    CosteC wrote:
    pawlik118 wrote:
    From what I remember, the fuse at the transformers, up to ~2.5VA, is not required. Perhaps this is due to the fact that the very thin wire of the primary winding is not able to carry the current that would give off power that could burn the insulation between the primary and secondary sides.
    e.g. Breve on their products

    I don't know such a recipe... It would be very strange, besides it assumes that there will be no magical failure anywhere else in the device that could lead to a fire..
    The fuse has two roles - protection against fire and protection against electric shock, of which it protects against electric shock only in specific cases - because depending on the position of the plug, the fuse can be on the neutral line.


    As a curiosity, I will add in the factory equipment of Polish production (metal housing) with 10VA transformers, the mains fuse on the primary side of the transformer was not always used either. The secondary windings of the transformer were always protected by fuses. E.g. tuner ELTRA T8010, T 3015, ZRK T7010, EQ DIORA FS 042.

    However, the V40.28 power supply in the Meratronik V640 multimeter does not have any fuse. (very often the transformer is damaged in them)

    In the case of devices in wooden or plastic housings (table radios), the transformer always had a fuse on the primary and secondary sides.

    Modern antenna power supply for continuous operation, which does not have any fuses.
    Power adapter with a cable and plug on a wooden surface. Transformer with wires and a capacitor on a wooden table.
  • #28 20650897
    yogi009
    Level 43  
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    Well, the function of the fuse was taken by the transformer. Such goovniane communist material savings in the face of Western economic sanctions.
  • #29 20653717
    dipol
    Level 34  
    Posts: 2598
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    Rate: 259
    I scrapped such a miracle when I started working at ZURiT in 1970. To make it easier to service the equipment, a multivibrator was added (to "sow" from early / early / mid-term) on germanium transistors. I had mastered the generators, because in the 4th grade of the technical school I had a shortwave transmitter made on 50 W lamps - for testing the mcz modulator of the transmitter.
    Me, a young goldfinch after a technical school, "old masters" stopped covering with caps so that "young" would not peep - and "borrow a generator" appeared.
    For them, transistors were the realm of SF. A helpful toy - I repaired over 200 radios a month. History has come full circle and has been rediscovered.
    I salute the young geeks.
    The lack of a fuse rather indicates a lack of elementary knowledge of health and safety.
    To protect myself from the "hot" mass, I still have a 500W safety transformer in my workshop from which I power the workbench. In this power supply there is a polymer fuse wound with the transformer winding.
    73!
  • #30 20653929
    Mateusz_konstruktor
    Level 37  
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    @dipole
    Which bulbs are suitable and which should be avoided?
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Topic summary

✨ The discussion centers on a homemade low-frequency workshop signal generator for servicing amplifiers and receivers, built as a simple sine-wave source with three fixed frequencies: 100 Hz, 1 kHz, and 10 kHz, powered from 230 V mains. The construction uses a steel enclosure with a plastic front panel, a mains transformer, and a ground-lift switch intended to break ground loops between the generator, the tested circuit, and an oscilloscope connected to protective earth. Participants debated the absence of a mains fuse, transformer protection, and the safety implications of relying on small transformer winding resistance or thermal protection. The circuit source was traced to an Elektronika Praktyczna 1/95 publication, and alternative generator ICs such as ICL8038 were mentioned as a possible design choice. The thread also covered practical details such as the use of foamed PVC/ABS for panels, lamp stabilization in generator circuits, and suitable indicator bulbs with low current ratings.
Summary generated by AI based on the discussion content.

FAQ

TL;DR: This DIY workshop generator delivers about 4 Vrms and uses a TL082 Wien bridge; as one commenter put it, "the bulb is correct." It is for amplifier and receiver servicing when commercial low-frequency generators cost too much. The practical issues are grounding, output hum, and whether to add a primary-side mains fuse. [#20642550]

Why it matters: This thread shows how to build a very low-cost audio test source that is useful in real bench work, while also exposing the safety and grounding decisions that matter most.

Option Waveforms Frequency approach Complexity Best use from thread
TL082 Wien bridge Sine only 100 Hz / 1 kHz / 10 kHz Very simple Low-distortion servicing source
ICL8038 Three waveforms Wider range Slightly more featured More versatile bench generator

Key insight: In a mains-powered metal generator, the enclosure should stay bonded to PE. The only switch that helps measurement problems is the one that interrupts the signal return path to reduce a ground loop, not the protective-earth bond.

Quick Facts

  • Output frequencies are fixed at 100 Hz, 1 kHz, and 10 kHz, selected by an isostat switch with RC elements. [#20641443]
  • The power supply uses a TS2/14 transformer and a Delon doubler, giving about 14 V DC plus about 11 V AC for the indicator lamp. [#20641443]
  • Output level adjusts from 0 to about 4 Vrms with a Telpod SP 1.2 potentiometer; amplitude is stabilized by a 60 V / 20 mA telephone bulb. [#20641443]
  • The enclosure cost was about a dozen zlotys, thanks to recycled sheet metal, reused mains cable, scrap plastic, and stock parts. [#20641443]
  • Bought parts explicitly named in the thread were 2 × 470 µF / 25 V / 105 °C Panasonic electrolytics and one TL082 dual op-amp. [#20641443]

How does the output ground switch work in a mains-powered signal generator with a non-isolated BNC socket and PE-connected metal chassis?

It works by interrupting the generator’s output return path, not by disconnecting protective earth from the metal case. The author said the chassis is permanently connected to PE, while the rear switch is used when the generator, tested circuit, and analog oscilloscope would otherwise create a loop through their grounded connections. With a standard BNC and metal case, that switch only makes sense in the signal ground path. [#20641606]

Why can a ground loop appear when a workshop generator and an analog oscilloscope are both connected to protective earth?

A ground loop appears because both devices can reference the same circuit through separate PE-linked paths. In the thread, the analog oscilloscope input socket was described as permanently connected to PE, and the generator chassis was also bonded to PE. When both then connect to the tested amplifier, loop current can flow in the signal return and add hum or misleading measurements. [#20641606]

What is a Wien bridge generator and why is it used to generate low-distortion sine waves at 100 Hz, 1 kHz, and 10 kHz?

A Wien bridge generator is an RC sine-wave oscillator that uses a frequency-selective bridge and nonlinear amplitude control, giving low distortion without complex circuitry. Here it was chosen because the EP 1/95 design is simple, uses a TL082, and provides three practical service frequencies: 100 Hz, 1 kHz, and 10 kHz. One commenter called its distortion value “almost immeasurable,” which captures why this topology is popular for audio servicing. [#20642995]

What is a Delon voltage doubler and how does it work in a simple transformer power supply?

A Delon voltage doubler is a rectifier circuit that uses two diodes and two capacitors to stack charging peaks, producing a higher DC output from an AC secondary. In this build, it follows a TS2/14 transformer and, with two filter capacitors, provides about 14 V DC for the generator while a separate roughly 11 V AC path feeds the indicator lamp. [#20641443]

How do you build a simple low-frequency sine wave generator based on the Elektronika Praktyczna 1/95 circuit with a TL082 op-amp?

Build it as a two-board mains device with a TL082 Wien bridge oscillator, a buffer stage, and a simple transformer supply. 1. Assemble the TS2/14 transformer supply with the Delon doubler. 2. Build the TL082 board with RC selection for 100 Hz, 1 kHz, and 10 kHz plus the lamp stabilizer. 3. Add the output level pot, BNC socket, and PE-bonded metal enclosure. The author completed the project over about one year because of parts shortages. [#20641443]

What role does a 60V/20mA telephone bulb play in amplitude stabilization in a Wien bridge oscillator?

It provides automatic gain control by changing resistance as the filament warms. In this generator, the 60 V / 20 mA telephone bulb sits in the Wien bridge feedback path, so a rising output increases lamp temperature and resistance, which reduces loop gain and stabilizes amplitude. The result is a cleaner sine wave than a fixed-gain RC oscillator usually gives. [#20641443]

Which bulbs work best for amplitude stabilization in RC audio generators, and which types should be avoided?

Use low-current incandescent bulbs, typically about 5–20 mA, because the thread stresses current more than rated voltage. Examples given were 12 V bulbs at 5–20 mA and telephone bulbs such as 24 V / 20 mA or 60 V / 20 mA. Avoid high-current lamps, because they are less sensitive in this role and make amplitude control poorer. As one reply put it, “the key parameter is its current, not voltage.” [#20656920]

Why are people concerned about the lack of a mains fuse in a generator powered by a TS2/14 transformer?

They are concerned because a fault in the transformer or wiring can overheat the device before anything external trips. Several replies challenged the author’s no-fuse choice and explicitly raised fire risk, including a case where a controller board burned until the installation protection operated. The concern is not only transformer failure, but any internal short on the 230 V side. [#20642060]

What are the fire and shock protection arguments for adding a primary-side fuse to a small mains transformer device?

A primary-side fuse limits fault energy and can reduce both fire risk and some shock scenarios. One commenter stated that a fuse has two roles: fire protection and, in specific cases, shock protection, though that second benefit depends on plug orientation because the fuse may end up in the neutral line. Even when small transformers sometimes omit a fuse, the thread repeatedly argues that adding one improves safety margin. [#20642060]

How does a plastic front panel made from ABS affect grounding and safety when the enclosure itself is metal and connected to PE?

It keeps the user-facing front surface non-conductive while the metal enclosure remains safely bonded to PE. The author later confirmed the front panel material is ordinary ABS plastic, and the original post states the box is permanently connected to the protective-earth conductor. That combination reduces accidental contact with grounded metal at the controls without removing chassis earthing. [#20647191]

What output level can you expect from this TL082-based generator, and how do you adjust it from zero to about 4 Vrms?

You can expect an adjustable output from 0 to about 4 Vrms. The thread says the level is set with a Telpod SP 1.2 carbon potentiometer, while a separate Telpod CN-15 cermet potentiometer sets the stabilized amplitude inside the oscillator. In practice, one control trims oscillator behavior and the other acts as the front-end output level control. [#20641443]

ICL8038 vs a Wien bridge TL082 generator — which is better for a simple workshop signal source for amplifier and receiver servicing?

The TL082 Wien bridge is better when you want a simple, low-distortion sine source for audio servicing. The ICL8038 was suggested because it offers three waveforms, wider range, and even offset adjustment, but that is a different priority. For amplifier and receiver alignment at 100 Hz, 1 kHz, and 10 kHz, the thread favors the Wien design’s simplicity and sine quality over broader feature count. [#20648594]

How can you wire the generator output and oscilloscope connections to avoid hum and grounding problems during amplifier testing?

Use one clear signal-return path and avoid duplicating the earth-referenced return through both instruments. 1. Keep the metal generator enclosure bonded to PE. 2. Connect the oscilloscope and generator grounds to the tested circuit carefully, watching for duplicate return paths. 3. If hum appears, use the generator’s output-ground switch to open the signal-return loop, not the chassis PE bond. This method addresses the exact loop problem discussed for analog oscilloscopes with PE-linked inputs. [#20641606]

Why is bulb current considered more important than bulb voltage in amplitude-stabilized sine wave generators?

Current matters more because the stabilization depends on how easily the filament’s resistance changes with heating. The thread explicitly says to choose a bulb with “as little current as possible,” and explains that its nonlinearity is what stabilizes the oscillator. That is why bulbs such as 20 mA telephone types are preferred even when their printed voltages differ, such as 24 V or 60 V. [#20642550]

What low-cost recycled materials and parts can be used to make a DIY workshop signal generator enclosure and power supply?

Use scrap steel sheet for the case, reused three-core mains cable, recycled plastic for the front panel, and stock components wherever possible. The author built the chassis from hand-cut and bent sheet metal, used a locally bought scrap sheet, and reused a mains cord from electronic waste. That kept the total cost to about a dozen zlotys, with only the transformer, TL082, and two 470 µF capacitors clearly bought new. [#20641443]
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