Hopefully someone with more knowledge of power supplies can answer this. I've built a variable DC power supply based on the LM317 regulator to power my guitar effects. I have a wall wart with 20VAC output connected to a full bridge rectifier I made from individual diodes. The rest of the circuit is one of the designs I've seen for the LM317. Some of the designs I've seen have additional diodes across the 3 pins of the regulator and some don't. Mine doesn't. When I power the circuit up, the DC voltage out responds well (~2-24VDC) when I turn the adjustment pot. The problem is that I also have an AC component that also responds to turning the pot. I understand that ripple can occur, but the AC voltage goes a high as 70v! Is this normal? I'd hate to fry one of my guitar effects. Any thoughts would be greatly appreciated.
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DC Power Supply LM317
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Latest activity · 22 Feb 2017DC Power Supply LM317
Re: DC Power Supply LM317
#2do you have a schematic? dont hook any load up to it before you figure out whats happening. something is wrong.[quote=Peacock post_id=140 time=1487770276 user_id=77]Hopefully someone with more knowledge of power supplies can answer this. I've built a variable DC power supply based on the LM317 regulator to power my guitar effects. I have a wall wart with 20VAC output connected to a full bridge rectifier I made from individual diodes. The rest of the circuit is one of the designs I've seen for the LM317. Some of the designs I've seen have additional diodes across the 3 pins of the regulator and some don't. Mine doesn't. When I power the circuit up, the DC voltage out responds well (~2-24VDC) when I turn the adjustment pot. The problem is that I also have an AC component that also responds to turning the pot. I understand that ripple can occur, but the AC voltage goes a high as 70v! Is this normal? I'd hate to fry one of my guitar effects. Any thoughts would be greatly appreciated.[/quote]
The diodes are for protection (some of the protection is for the LM317 and some is for the load.
you might have a capacitor that is either bad or has a loose connection.
what is the output voltage and current draw supposed to be for this effects generator?