Author Topic: Building my own preamp power supply. Not working so far.  (Read 14609 times)

Offline Wavedude

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Re: Building my own preamp power supply. Not working so far.
« Reply #30 on: December 17, 2010, 04:37:04 PM »
They were out of the 34V at mouser, so I just went with the 36V Rob suggested. Its not much of a difference, and it might help to have that extra current. It's being processed and shipped as we speak :)

Until it gets here, I have all the parts for the rest of the DC power supply circuit. I hope everything works well.
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Offline Rob A

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Re: Building my own preamp power supply. Not working so far.
« Reply #31 on: December 17, 2010, 05:19:14 PM »
So what size (in microfarads) filter caps did you select? It's not real sensitive to the value, BTW--the voltage reg IC will cover the ripple.

Did you get bypass caps for the LM317? What are you building this on, perfboard?

Here's a 5V one that I made a decade or so ago using a 7805:



Heatsink is NOT optional





I am also hoping you got a fuse for the mains side, 1A should do.

Offline Rob A

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Re: Building my own preamp power supply. Not working so far.
« Reply #32 on: December 17, 2010, 05:21:44 PM »
Hehe if you hook the caps up backwards, you get this:


Offline Wavedude

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Re: Building my own preamp power supply. Not working so far.
« Reply #33 on: December 17, 2010, 05:53:34 PM »
Their 1000uf and 100uf eCaps and two .1 ceramic caps.

I didn't get a fuse, I'll make sure to get one. Mine is turning out a lot like yours. Its just like the one in the schematic sean posted. Except Im using a 33 ohm resistor in place of the 10k pot.
I'm also waiting on the transformer to come in of course.

Where should I put the fuse? It wasn't on the schematic.
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Offline Rob A

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Re: Building my own preamp power supply. Not working so far.
« Reply #34 on: December 17, 2010, 07:51:03 PM »
Fuse must go in the hot lead on the mains side. Must.

Offline Wavedude

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Re: Building my own preamp power supply. Not working so far.
« Reply #35 on: December 18, 2010, 12:37:36 AM »
Ok, before or after the the transformer?

...I'm sounding like such an airhead right now, haha. Sorry, I've never really known to much about fuses, and the tutorials online don't give any info about them.
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Offline Rob A

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Re: Building my own preamp power supply. Not working so far.
« Reply #36 on: December 18, 2010, 08:55:06 AM »
The primary winding of the transformer is connected to mains power. Mains power is a hot and a neutral connector. Put the fuse in so that it interrupts the hot when it opens--that is its purpose. It keeps you alive if the device fails. So it needs to interrupt the mains power to the transformer. Make sense? Please ask if it needs further clarification--this is a crucial part of the build.