Any electronics boffins here?

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esox

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May 15, 2003
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I like to listen to the radio whilst tinkerin` in the garage.
Due to the violent destruction after the recalcitrant piece of crap ****** me off one time too many sad demise of the mini hi-fi that i used to have installed in the workshop i now find myself listening to an ancient car radio-cassette rigged up to the battery charger...

The trouble is that there is an audible background hum through the speakers which is inaudible during music play - as long as a reasonable volume level is selected, but annoyingly present whilst listening to The Archers interesting and factual documentaries from the BBC .

The hum is (i assume) coming from the battery charger and i`m guessing it needs some kind of capacitor or other doo-dah to smooth out the power supply?

Does anyone know what i need to do to electronically eradicate this musical malady?
 
The hum is indeed coming from the battery charger.
The bad news is that it is highly unlikely you will ever totally get rid of it as a charger just isn't designed to give a clean supply as, when performing its designed function, it just doesn't need to.
A large electrolytic (with a resistor) across the output, and a decent choke in line with the output might reduce the hum, but tbh I think you will just be wasting your time, and money.
How about a bluetooth speaker and google play/tune in radio on your phone?
 
Ted's onto something here: the DC output from a battery charger is probably as rough as a dog's a**e, complete with 50Hz hum. It won't matter to a lead-acid battery.

A car radio won't needs masses of current, a simple regulated bench top power supply with do the job, if you're up for lopping off the connector and splicing the wires to a couple of spade connectors..

https://www.amazon.co.uk/dp/B015ONUNKE/?tag=amazon0e9db-21

Cheers,

Gaz
 
Hi,
Can you not find a used radio with mains input at your local car boot for perhaps a fiver or even less? I was going to suggest, that, if you must use a battery charger, then find an old 12 volt battery, charge it, and use your old radio off of the battery. But the reality is, and being pragmatic to just get yourself a radio with a mains input and job done.
Steve
 
You might reduce the hum by putting a car battery into the circuit.

Failing that, charge battery (without radio) then run radio from battery.
 
You may need a smoothing capacitor across the 12v supply from the battery charger. Easiest was is put a 12v battery in the circuit, but make sure it can handle the charge or you may boil the battery. i.e. the battery must be in reasonable condition. or if you want to get technical Smoothing Capactitors | REUK.co.uk
 
Won't matter for long; 17 volts of half wave rectification will kill it soon enough, I expect. Either plug it into a charged battery or build a smoothed and regulayed full wave rectified circuit instead. Hint: if you don't know what I am on about, use the battery.
 
Cheers guys.
Yep, buying a cheapo radio for the garage seems to be the sensible answer, but for someone like me who likes to `upcycle` and use whatever i have to hand it goes against my religion!
I guess i`ll have to endure the hoi-polloi at a car boot sale sometime soon..
 

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