Need a 12.6 VDC power supply schematic

Dmeister · 21st May 2011, 02:32 PM

Hello everyone. I recently finished my hybrid 12AU7/IRF510 headphone amp, and it sounds wonderful

The problem is, there's a bit of hum every once in a while, and I think it's the power supply that's the problem. Here's a schematic for it:

Now I've tried building that schematic 2 times, but it outputs about 15 VDC

I'm looking for a regulator schematic that inputs about 15-20 VDC and outputs 12.6 VDC. If anyone has any suggestions I would be really thankful

TG · 21st May 2011, 02:40 PM

Changing RR1 from 120 to 270 Ohm will be quite enough.

Dmeister · 21st May 2011, 02:50 PM

Quote:

Originally Posted by TG

Changing RR1 from 120 to 270 Ohm will be quite enough.

Thanks, I'll do that and report back here

Dmeister · 28th May 2011, 05:05 PM

I changed RR1 but it still outputs about 15 VDC. I don't think it's the LM317, since I tried 3 different ones. Can anyone give me another schematic for a 12.6 VDC regulator ?

Dmeister · 28th May 2011, 05:17 PM

Can anyone please help me ? I need this quite soon...

TG · 28th May 2011, 05:34 PM

What voltage is at the LM317's IN terminal?

tomchr · 28th May 2011, 06:00 PM

The schematic is fine. The issue is with the resistor values. Try these values:

RR1 = 220 ohm
RR2 = 1500 ohm
RR3 (pot) = 1000 ohm

The output voltage is Vout = 1.25*(1+(RR2+RR3)/RR1) in your case. Hence, above values should yield an adjustment range of 9.8 ~ 15.5 V.

~Tom

Andy5112405 · 06:14 PM

I think your Vin is too low, the LM317 needs about 3V to operate. As an experiment try increasing Vin, try about 18VDC that should prove the point.

TG · 28th May 2011, 06:27 PM

Initial resistor values (with RR1 = 270 Ohm) are fine too.
I have a suspicion that DR3 and/or DR2 are mistakenly reversed.

With too low Vin LM317 should output about Vin-1.2..2V depending on load, so I believe this is not the case.

Dmeister · 28th May 2011, 08:35 PM

It seems the trim potentiometer wasn't properly working. Well, actually, not one, but THREE of them ! I am that unlucky. I bought a proper trim potentiometer so now it works.

21st May 2011, 02:32 PM	#1
Dmeister diyAudio Member Join Date: Aug 2010	Need a 12.6 VDC power supply schematic Hello everyone. I recently finished my hybrid 12AU7/IRF510 headphone amp, and it sounds wonderful The problem is, there's a bit of hum every once in a while, and I think it's the power supply that's the problem. Here's a schematic for it: Now I've tried building that schematic 2 times, but it outputs about 15 VDC I'm looking for a regulator schematic that inputs about 15-20 VDC and outputs 12.6 VDC. If anyone has any suggestions I would be really thankful

28th May 2011, 06:11 PM	#8
Andy5112405 Banned Join Date: Nov 2006 Location: Torpoint	I think your Vin is too low, the LM317 needs about 3V to operate. As an experiment try increasing Vin, try about 18VDC that should prove the point. Last edited by Andy5112405; 28th May 2011 at 06:14 PM.

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21st May 2011, 02:40 PM	#2
TG diyAudio Member Join Date: May 2002 Location: Kiev, Ukraine	Changing RR1 from 120 to 270 Ohm will be quite enough.

28th May 2011, 05:05 PM	#4
Dmeister diyAudio Member Join Date: Aug 2010	I changed RR1 but it still outputs about 15 VDC. I don't think it's the LM317, since I tried 3 different ones. Can anyone give me another schematic for a 12.6 VDC regulator ?

28th May 2011, 05:17 PM	#5
Dmeister diyAudio Member Join Date: Aug 2010	Can anyone please help me ? I need this quite soon...

28th May 2011, 05:34 PM	#6
TG diyAudio Member Join Date: May 2002 Location: Kiev, Ukraine	What voltage is at the LM317's IN terminal?

28th May 2011, 06:00 PM	#7
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	The schematic is fine. The issue is with the resistor values. Try these values: RR1 = 220 ohm RR2 = 1500 ohm RR3 (pot) = 1000 ohm The output voltage is Vout = 1.25*(1+(RR2+RR3)/RR1) in your case. Hence, above values should yield an adjustment range of 9.8 ~ 15.5 V. ~Tom

28th May 2011, 06:27 PM	#9
TG diyAudio Member Join Date: May 2002 Location: Kiev, Ukraine	Initial resistor values (with RR1 = 270 Ohm) are fine too. I have a suspicion that DR3 and/or DR2 are mistakenly reversed. With too low Vin LM317 should output about Vin-1.2..2V depending on load, so I believe this is not the case.

28th May 2011, 08:35 PM	#10
Dmeister diyAudio Member Join Date: Aug 2010	It seems the trim potentiometer wasn't properly working. Well, actually, not one, but THREE of them ! I am that unlucky. I bought a proper trim potentiometer so now it works.

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