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Wrong transformer?

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qimqim

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I have a radio but cannot find the transformer that allows me to connect it to the mains. There is a mention of 4.5v where the transformer plugs into the radio. My question is: what happens if I plug a different transformer rated either higher or lower? Does it damage the radio? Will any transformer rated at 4.5v be acceptable?

I live in Europe where the current is 240v

Thank you
 
qimqim said:
I have a radio but cannot find the transformer that allows me to connect it to the mains. There is a mention of 4.5v where the transformer plugs into the radio. My question is: what happens if I plug a different transformer rated either higher or lower? Does it damage the radio? Will any transformer rated at 4.5v be acceptable?

I live in Europe where the current is 240v

Thank you
hi,
Is the power connector on the radio a circular 2 pin type.?

Are there any symbols marked on the radio connector indicating the voltage and polarity.?

Some radio's expect a 'dc' 4.5V input and others an 'ac' 4.5V input.
This will determine what type of mains power supply you need.
You can buy 'wall wart' mains plug psu's for a wide range of selectable voltages.
 
It is a Sony ICF-2001 (quite old...)

The socket on the radio is a circular 1-pin connection and it says DC In 4.5V and below the socket a little diagram for Polarity: it is an horizontal diagram qith + on the left and - on the right. Both are enclosed in a circle and led by an horizontal line to a middle larger circle. This circle is open on the right allowing the - sign to go inside it.

Does this help?

Thank you very much
 
Hi,

Is the + connected by the line to the middle? or is it the - that goes to the middle of the circle? This will indicate the polarity.
You should be able to buy a "wall wart" transformer to suit the radio. With some it is possible to switch the polarity and the voltage to suit your requirements. Maybe try ebay for something suitable.
 
it is the - that goes to the middle of the circle; so, it seems to be negative polarity, right?

Where I am there is no "wall wart" but I have several transformers laying around. What I need to know is whether I can use a transformer that has a higher or a lower output (assuming that they all have the same polarity.

Thanks
 
Just checked the service manual...
It says 4.5VDC 95mA - FM, 225mA - AM... so you'd need around a 300+mA adaptor. Yes it is a centre negative input.
There is a linear DC/DC converter following the input so if you raise the input voltage, it's going to be raised by the same factor through the circuit. I.E. It doesn't have a voltage regulator.
So try not to go above 5VDC.
The polarity is easily solved, if you have a plug pack that is 5VDC 300mA or whatever, cut the wires and switch them if it is a centre positive one. Ensure to wrap them nicely in electrical tape or heat-shrink so they don't short.

While they're cut, you can add a ferrite bead to stop any rubbish coming through =)
 
Great, thanks.

But what if I use a transformer with less than 5V DC? Would it damage the radio? Would it work?


For instamce: I have in front of me two transformers:

Input 230V - 50 Hz
Output 9V - 1A 9 VA

Input 230V - 50 Hz 0.13A 22W
Output 24V - 500 mA 14.4 W


Thank you very much.
 
Last edited:
You can't use anything less than 4 or above 5. If you use 4, you will need slightly more current.
 
Sorry, I amended my last post. I'm not sure if you saw it.

Anyway, I will go hunting for something between 4 and 5. I think somewhere I have one with selectble output. Would that be ok?

Thanks
 
qimqim said:
I have a radio but cannot find the transformer that allows me to connect it to the mains. There is a mention of 4.5v where the transformer plugs into the radio. My question is: what happens if I plug a different transformer rated either higher or lower? Does it damage the radio? Will any transformer rated at 4.5v be acceptable?

I live in Europe where the current is 240v

Thank you
You mean the voltage is 240V.

What sort of transformer is this?

Are you talking about one of those heavy wall plugs?

What is the current rating?

Does is output AC or DC?
 
I have several, but right in front of me:

Input 230V - 50 Hz
Output 9V - 1A 9 VA

Input 230V - 50 Hz 0.13A 22W
Output 24V - 500 mA 14.4 W

Thanks
 
Do those have AC or DC outputs?

What about the radio?

Does it say it requires 9V AC or DC and does it have a current rating?

The 9V 1VA looks your best bet at the moment.
 
Please see Erosennin above:
Just checked the service manual...
It says 4.5VDC 95mA - FM, 225mA - AM... so you'd need around a 300+mA adaptor. Yes it is a centre negative input.
There is a linear DC/DC converter following the input so if you raise the input voltage, it's going to be raised by the same factor through the circuit. I.E. It doesn't have a voltage regulator.
So try not to go above 5VDC.
The polarity is easily solved, if you have a plug pack that is 5VDC 300mA or whatever, cut the wires and switch them if it is a centre positive one. Ensure to wrap them nicely in electrical tape or heat-shrink so they don't short.

While they're cut, you can add a ferrite bead to stop any rubbish coming through =)
 
Sorry, I was talking nonsense, you need a regulator, the 9V adaptor on it's own will fry it.

Use the 9V adaptor with an LM7805 on the output which will provide 5V and which isn't any higher than an unregulated adaptor will give.
 
hi,
Where in Europe do you live, we maybe able to give a supplier and part number for +4.5V 500mA mains plug type psu.

A transformer on its own is not suitable for the radio.
 
Hi

I'm in Portugal at the moment, but the radio will go with me to the UK (via Malta...)

Why do you say the transformer is not enough?

Problem is, though, that I am not sure that the radio works. And if it does not I don't want to cart it around across half of Europe. If you say a transformer is not enough, how could I try it out?

Thanks
 
Last edited:
qimqim said:
Hi

I'm in Portugal at the moment, but the radio will go with me to the UK (via Malta...)

Why do you say the transformer is not enough?

Problem is, though, that I am not sure that the radio works. And if it does not I don't want to cart it around across half of Europe. If you say a transformer is not enough, how could I try it out?

Thanks

hi,
The radio requires a 'dc' supply, a transformer only has an 'ac' output.
A transformer would require a rectifier, smoothing and a 4.5v voltage regulator.

Does this help.

You could plug in a 4.5V battery, be sure to observe the correct polarity, this will give a quick radio check.
 
Use this circuit to power your radio. The 5V supply shouldn't damage the radio, three fully charged AA cells would give up to 4.8V and think that it's at least rated to 5V.

**broken link removed**
 
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