Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [substitution]

Involving or pertaining to electronic component or circuit substitution.

43 questions
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Can a thyristor be built from two transistors?

Supposedly, an SCR/thyristor is just a simple, four layer PNPN semiconductor. If that's the case.. When a circuit calls for a SCR/thyristor, and there isn't one available, can it be substituted by (i.e. crafted from) two BJTs (or other discrete…
voices
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Question about long-term support for legacy board designs

This question is summarized from a discussion on the Electrical Engineering StackExchange chat. It is reproduced here in hopes to generate a discussion with long-term value Question for anyone with experience with long (> 30 years) life cycle…
Anindo Ghosh
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No germanium diode available for small crystal radio -- can active components handle the task?

I know that germanium diodes are trivial to find online, but as this is for a demonstration I'd rather not spend $6-7+ on shipping for a single 5 cent part for a project that's academic in exercise anyway. RadioShack has proven stereotypically…
Bryan Boettcher
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Can I safely substitute a 4.7uF cap for a 5uF cap?

I'm working on a circuit that calls for a couple 5uF caps. I have 50v and 25v 4.7uF at my workbench. No cap voltage is specified in a schematic or parts list. The circuit has 12VDC coming in, one negistor that'll be connected to the path of the caps…
dwwilson66
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Can an X-class safety capacitor be used in series with a load (i.e. where steady current flows through it)?

Many applications that need a low voltage supply that is not isolated from the mains use a capacitive dropper circuit to get it -- an example is shown in the schematic below. simulate this circuit – Schematic created using CircuitLab In this type…
ThreePhaseEel
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How would a transistor's hFE affect a phase shift oscillator?

I have a phase shift oscillator circuit from a drum machine that I would like to reproduce as faithfully to the original as possible. My problem is that the 40 year old design uses a transistor (2N3394) that is no longer available. But... the others…
Jay
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Is there a relevant difference between these capacitors?

I am planning to try designing a board that incorporates a switch-mode DC-DC converter, using this Texas Instruments reference design for their TPS54386PWPR regulator part: The bill of materials for the Texas Instruments circuit specifies C1 as a…
Kaelin Colclasure
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Getting a small AC "reference" from a DC power supply?

I have a 1970s-vintage video generating board that I'd like to do some work with. I do not have the PSU that it was meant to be connected to. The board wants +/-5V, -12V DC, plus a small 6V AC "reference" rail that shares the same common/ground…
BZo
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MOSFETs not activating - is this transistor the problem and can it be subbed?

I'm trying to repair a DC motor controller that moves a caravan. The positive side is relay switched, and it turned out that the negative side of the motor supply was switched by a pair of IRF3205 MOSFETs on each side (two motors, four MOSFETs) and…
Caius Jard
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How to choose an alternative for a specific BJT transistor?

I'm trying to reproduce some circuits with electronic pieces that I've at home. Unfortunately I miss some recommended transistors so I'm trying to understand how to replace them with an alternative transistor and overcome this problem. How can I…
G M
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What is a secondary transformer?

On a number of projects I'm building, there's a transformer between wall power and device power. In the parts lists, the transformers are usually designated by "12v secondary transformer" or "18v 4a Secondary Transformer". Because the flow goes from…
dwwilson66
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How do I determine if I can safely substitute potentiometers?

I've got a number of audio projects on the workbench, and of course, each of them requires different potentiometers. Instead of waiting for another box o' parts to arrive, can I substitute? What are the rules of thumb for that? While my first…
dwwilson66
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Need advice in repairing my obsolete 44-year-old OEM Ovation acoustic guitar preamp

Preamp (9VDC): 6 capacitors (4 MMKO box film caps and 2 CAPAR axial 4.7uF 50v electrolytic caps), 1 3-pin junction transistor (M2N5458), 2 unknown transformers, 5 resistors. See attached image. Problem: The volume when plugged in has reduced over…
tayglo
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Do circuit reclosers of substations respond to any fault on the low voltage side of distribution transformer?

As I don't have any practical experience in power distribution networks, I'm pretty confused about a few things. Typically a lot of transformers are connected to an 11KV distribution line ( 11KV feeder.) For an 11KV/440V three-phase transformer, if…
Sadat Rafi
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Diode substitution for FMXG26S

I been hunting for an equivalent for a Diode in TV Power Supply - its a FMXG26S. Does anyone have any idea of an equivalent? Or where I can look one up? The datasheet advises the following for the…
Neale Francis
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