Replacing Audio Transformers in Radio Receivers

[michael1978]

hello
can somebody help me,
what can i use in place of audio transformer
because i was in electronics shop
the man he told they don't use anymore audio transformer in radio receiver

what to use in place of audio transformer?thnx

 

[jedishrfu]

Do you have the original audio transformer?

Some sources on the internet suggest removing some of the tape around the transfer where you might find a blown fuse that can be replaced.

https://electronics.stackexchange.c...pair-how-can-i-find-a-replacement-transformer

Here's some more repair info:

https://www.premierguitar.com/articles/Why_and_How_to_Replace_Your_Amplifiers_Output_Transformer

 

[michael1978]

Do you have the original audio transformer?

Some sources on the internet suggest removing some of the tape around the transfer where you might find a blown fuse that can be replaced.

https://electronics.stackexchange.c...pair-how-can-i-find-a-replacement-transformer

Here's some more repair info:

https://www.premierguitar.com/articles/Why_and_How_to_Replace_Your_Amplifiers_Output_Transformer

I have no audio transformer, i want to build on radio receiver, and i go to buy components like audio transformer, he told me they don't use anymore, what i have to use n place of audio transformer

 

[jedishrfu]

Like this one or something more powerful:

http://www.instructables.com/id/Radio-receivers-from-scratch/

or this one:

http://boyslife.org/hobbies-projects/projects/40/catch-some-radio-waves/

 

[michael1978]

Like this one or something more powerful:

http://www.instructables.com/id/Radio-receivers-from-scratch/

or this one:

http://boyslife.org/hobbies-projects/projects/40/catch-some-radio-waves/

dont take me wrong, i know that

but i have a problem, with which component to replace those audio transformer

T1: audio transformer 10K primary or 2K secondary
T2: audio transformer 120 to 500 primary , 8 secondary
T3: audio transformer 10K primary 10K or 7K secondary
T4: audio transformer primary 1.5K , secondary 600 CT
T5: audio transformer primary 4.8 CT, secondary 8

because in electronics shop , where i was, e told me they don't use anymore audio transformerand i want to build transistor radio

 

[NFuller]

the man he told they don't use anymore audio transformer in radio receiver

That's a plain lie. Plenty of devices still use transformers in the audio output circuit.

and i want to build transistor radio

In that case, the transformer you want will depend on the resistance of the speakers it is driving (likely 4 or 8 Ohms) and the design of the amplifier driving it. Do you have a schematic of the audio output stage?

 

[Averagesupernova]

because in electronics shop , where i was, e told me they don't use anymore audio transformerand i want to build transistor radio

Don't take this the wrong way, but I suspect they just did not want to bother with you.
-
Listen to what others here tell you. They know what they are talking about.

 

[tech99]

dont take me wrong, i know that

but i have a problem, with which component to replace those audio transformer

T1: audio transformer 10K primary or 2K secondary
T2: audio transformer 120 to 500 primary , 8 secondary
T3: audio transformer 10K primary 10K or 7K secondary
T4: audio transformer primary 1.5K , secondary 600 CT
T5: audio transformer primary 4.8 CT, secondary 8

because in electronics shop , where i was, e told me they don't use anymore audio transformerand i want to build transistor radio

We have suppliers in the UK such as Maplin, on the high street, that do T4 and T5 so I think they would be available on the web. I have also used small, low voltage mains transformers for audio purposes. You can find the turns ratio from the rated voltages. These days people try to avoid transformers in designs, as they have become expensive and big compared with the semiconductors, but in previous times transformers were used all over the place because they were reliable and reproducible. It is just the technology fashion of the moment. Everything was steam before that.

 

[michael1978]

That's a plain lie. Plenty of devices still use transformers in the audio output circuit.

In that case, the transformer you want will depend on the resistance of the speakers it is driving (likely 4 or 8 Ohms) and the design of the amplifier driving it. Do you have a schematic of the audio output stage?

How can be possible, he is a good man, i have a schematic i will put here

 

[michael1978]

Don't take this the wrong way, but I suspect they just did not want to bother with you.
-
Listen to what others here tell you. They know what they are talking about.

but how is possible, to bother, he say simple they don't use anymore audio transformer,
because i also find strange, this book which i am reading, is very good bood to build radio transistor

and i told him this book is from 2013 is not old book,

 

[michael1978]

the first
https://www.mupload.nl/img/eccf7t9nnfrau.png
the second
https://www.mupload.nl/img/qlmllyb0wq8da.png

but there are still other circuits which they use

T1: audio transformer 10K primary or 2K secondary
T2: audio transformer 120 to 500 primary , 8 secondary
T3: audio transformer 10K primary 10K or 7K secondary
T4: audio transformer primary 1.5K , secondary 600 CT
T5: audio transformer primary 4.8 CT, secondary 8

I take from the book build you own radio transistor
can somebody help me where to buy and how to select it, i am a beginner, i never buy till now transformers
thnx
have a nice wekend

 

[jim hardy]

Take a look at these
http://www.hammondmfg.com/5caud.htmBetter electronic suppliers will have them
https://www.alliedelec.com/view/search?keyword=audio transformer

and you might salvage one from a thrown away radio.

 

[NFuller]

the first
https://www.mupload.nl/img/eccf7t9nnfrau.png
the second
https://www.mupload.nl/img/qlmllyb0wq8da.png

but there are still other circuits which they use

T1: audio transformer 10K primary or 2K secondary
T2: audio transformer 120 to 500 primary , 8 secondary
T3: audio transformer 10K primary 10K or 7K secondary
T4: audio transformer primary 1.5K , secondary 600 CT
T5: audio transformer primary 4.8 CT, secondary 8

I take from the book build you own radio transistor
can somebody help me where to buy and how to select it, i am a beginner, i never buy till now transformers
thnx
have a nice wekend

You should first consider what the impedance is of the speaker you will be driving. The output impedance of the secondary should match the impedance of the speaker.

The primary coil of the transformer is the load that the transistor will drive. The constraints on the primary resistance are that it must be large enough that the maximum current through the transistor stays below its maximum design value and small enough that distortion of the audio signal is minimal. I would say anything between a few hundred ohms to a kilo-ohm is fine. If you are interested in finding the specific behavior of the audio output, then you will need to draw up the load line for the output stage. If you have never done this before then here is a brief introduction
https://www.tutorialspoint.com/basic_electronics/basic_electronics_transistor_load_line_analysis.htm

 

[NFuller]

but how is possible, to bother, he say simple they don't use anymore audio transformer,

Transformers still find use in audio output circuits because speakers present such a low impedance load to the circuit. Although modern semiconductors can drive low impedance loads, most transistors will not be happy trying to dump hundreds of milliamps into a speaker. A transformer fixes this problem by turning the low impedance load of a speaker into a high impedance load on the transformer primary.

 

[CWatters]

What sort of electronics shop? I don't know any in my country that would sell audio stage transformers (apart from output stage maybe). You would have to go to a professional electronic components distributor.

Mouser perhaps..
https://www.mouser.co.uk/Mobile/Passive-Components/Transformers-Audio-Signal/_/N-5gbg

 

[michael1978]

Hello is possible to use in place of audio transformer , an ic audio power amplifier, one friend he told me
i relly find difficult to find audio transformer, i have no experience

 

[michael1978]

Take a look at these
http://www.hammondmfg.com/5caud.htmBetter electronic suppliers will have them
https://www.alliedelec.com/view/search?keyword=audio transformer

and you might salvage one from a thrown away radio.

hello can i use ic audio power amp in place of audio transformer

 

[michael1978]

What sort of electronics shop? I don't know any in my country that would sell audio stage transformers (apart from output stage maybe). You would have to go to a professional electronic components distributor.

Mouser perhaps..
https://www.mouser.co.uk/Mobile/Passive-Components/Transformers-Audio-Signal/_/N-5gbg

can i use maybe in place ic audio power amp

 

[michael1978]

What sort of electronics shop? I don't know any in my country that would sell audio stage transformers (apart from output stage maybe). You would have to go to a professional electronic components distributor.

Mouser perhaps..
https://www.mouser.co.uk/Mobile/Passive-Components/Transformers-Audio-Signal/_/N-5gbg

can i use ic audio power amp

 

[michael1978]

Transformers still find use in audio output circuits because speakers present such a low impedance load to the circuit. Although modern semiconductors can drive low impedance loads, most transistors will not be happy trying to dump hundreds of milliamps into a speaker. A transformer fixes this problem by turning the low impedance load of a speaker into a high impedance load on the transformer primary.

can i use ic audio power amp

 

[michael1978]

You should first consider what the impedance is of the speaker you will be driving. The output impedance of the secondary should match the impedance of the speaker.

The primary coil of the transformer is the load that the transistor will drive. The constraints on the primary resistance are that it must be large enough that the maximum current through the transistor stays below its maximum design value and small enough that distortion of the audio signal is minimal. I would say anything between a few hundred ohms to a kilo-ohm is fine. If you are interested in finding the specific behavior of the audio output, then you will need to draw up the load line for the output stage. If you have never done this before then here is a brief introduction
https://www.tutorialspoint.com/basic_electronics/basic_electronics_transistor_load_line_analysis.htm

can i use ic audio power amp

 

[michael1978]

Take a look at these
http://www.hammondmfg.com/5caud.htmBetter electronic suppliers will have them
https://www.alliedelec.com/view/search?keyword=audio transformer

and you might salvage one from a thrown away radio.

can i use ic audio power amp

 

[jim hardy]

can i use ic audio power amp

Sure. Plenty of them around. LM386 will drive a small speaker and is very easy to use, will operate fine from a 9v battery..
http://www.ti.com/lit/ds/symlink/lm386.pdf
several hobby kits available with a printed circuit board.

This kit and 6 inch speakers in a proper enclosure will fill a room with music.
http://www.kitsrus.com/pdf/k88.pdf
i've built several. Friends raved about the high quality sound.

old jim

 

[NFuller]

can i use ic audio power amp

Yes, you can use these without an audio transformer.

 

[michael1978]

Sure. Plenty of them around. LM386 will drive a small speaker and is very easy to use, will operate fine from a 9v battery..
http://www.ti.com/lit/ds/symlink/lm386.pdf
several hobby kits available with a printed circuit board.

This kit and 6 inch speakers in a proper enclosure will fill a room with music.
http://www.kitsrus.com/pdf/k88.pdf
i've built several. Friends raved about the high quality sound.

old jim

thank you man, you make me easy now, because this audio transformer i don't understand

 

[michael1978]

Yes, you can use these without an audio transformer.

thank you, now its easy for me...