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 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?
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.
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.
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.
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 =)
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?
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 =)
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?
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?
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.