Quote:
Originally Posted by Electronpusher0
The LM317 has a max input voltage of 40V so it is unlikely that the battery charger is giving too high an output for the regulator.
Does the regulator get hot before it blows?
Do you have the recomended protection diode across the regulator (1N4002 Cathode to input, Anode to output)?
Are you using the original metal rectifiers in the charger (you did say it was old), if so change them to silicon types (if the 4700uf is getting hot it indicates that one of the rectifiers is breaking down and ac is getting onto the capacitor.
Have you got a 0.1uf capacitor close to the input terminal (input to 0V), this is recomended
"Ci is recommended, particularly if the regulator is not in close proximity to the power-supply filter capacitors. A 0.1-µF or 1-µF ceramic or tantalum capacitor provides sufficient bypassing for most applications, especially when adjustment and output capacitors are used."
And don't forget the capacitor from the adjustment terminal to 0V.
Just a few thoughts
Peter
Edit, looks like we are all thinking along the same lines.
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No protection diode across the regulator, The rectifier diodes are silicon, And the only capacitors in the circuit besides the smoothing capacitor are a 1uf 50v on the output and a 0.1uf on the input,
Edit, No it's not getting hot,