Mini audio transformer, where are you?

Makaram

Member

• Jan 25, 2012

• #1

this is an old radio which I was told should contain a mini audio transformer but I don't see it! is it there?

 

ronsimpson

Well-Known Member

Most Helpful Member

• Jan 25, 2012

• #2

You should not believe everything you are told.

 

ronv

Well-Known Member

Most Helpful Member

• Jan 25, 2012

• #3

Don't see one. It may have a large capacitor to the speaker and not a transformer.

 

JimB

Super Moderator

Most Helpful Member

• Jan 25, 2012

• #4

this is an old radio

Click to expand...

But it is not old enough, you need something from before about 1970.

JimB

 

Makaram

Member

• Jan 25, 2012

• #5

ahhh k thanks guys

 

audioguru

Well-Known Member

Most Helpful Member

• Jan 25, 2012

• #6

I got a portable transistor radio as a gift in about 1958 that used audio transformer.

Here is the schematic of a 1955 Philips audio amplifier that used an expensive mini output transformer but they avoided using an expensive mini driver transformer:

 

Attachments

• Philips transistor amp-1955.PNG

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JimB

Super Moderator

Most Helpful Member

• Jan 25, 2012

• #7

A trip down memory lane there AG.

I think there is a mistake in that schematic, the OC71 is a PNP transistor, the power rail at the top of the schematic should be the -ve rail.

In a PNP, the collector is negative with respect to the emitter.

JimB

 

audioguru

Well-Known Member

Most Helpful Member

• Jan 25, 2012

• #8

JimB said:

I think there is a mistake in that schematic, the OC71 is a PNP transistor, the power rail at the top of the schematic should be the -ve rail.

In a PNP, the collector is negative with respect to the emitter.

JimB

Click to expand...

I agree that in 1955 Philips got the polarity of the battery wrong.