Acdc voltage issue

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desol
Posts: 10
Joined: Mon Feb 22, 2010 7:36 am

Acdc voltage issue

Post by desol »

Hi there

I have a version 2 or 3 ACDC. I want to use it to power a couple ADR scamp modules which require +/- 28vdc.

The acdc has been sitting in a drawer for a while. I powered it up today and for some reason i can only adjust the phantom voltage up to about 33vdc and the bipolar rails only up to around +/- 16vdc...but not any higher. I have a 30va toroid powering it...primaries in parallel, secondaries in series for 24vac.

Not sure what could be the problem here. Maybe one of the capacitors? Any help appreciated...thanks!

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Joe Malone
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Re: Acdc voltage issue

Post by Joe Malone »

desol wrote:Hi there

I have a version 2 or 3 ACDC. I want to use it to power a couple ADR scamp modules which require +/- 28vdc.

The acdc has been sitting in a drawer for a while. I powered it up today and for some reason i can only adjust the phantom voltage up to about 33vdc and the bipolar rails only up to around +/- 16vdc...but not any higher. I have a 30va toroid powering it...primaries in parallel, secondaries in series for 24vac.

Not sure what could be the problem here. Maybe one of the capacitors? Any help appreciated...thanks!
This will be due to how you have wired the transformer secondary to the AC/DC kit. You need to wire the 24vac (no centre tap connected) between 0v and one of the AC in to make the voltages you need.

It sounds like you have the the 24vac wired between the 2 x AC in with centre tap to 0v which will make the voltages you mention.

The ideal transformer would have been a 2 x 22vac wired as 44vac centre tapped wired to 0v and each 22vac end to a AC in each.
Joe :-)
JLM Audio
Capturing Audio without Injury

desol
Posts: 10
Joined: Mon Feb 22, 2010 7:36 am

Re: Acdc voltage issue

Post by desol »

Joe Malone wrote:
desol wrote:Hi there

I have a version 2 or 3 ACDC. I want to use it to power a couple ADR scamp modules which require +/- 28vdc.

The acdc has been sitting in a drawer for a while. I powered it up today and for some reason i can only adjust the phantom voltage up to about 33vdc and the bipolar rails only up to around +/- 16vdc...but not any higher. I have a 30va toroid powering it...primaries in parallel, secondaries in series for 24vac.

Not sure what could be the problem here. Maybe one of the capacitors? Any help appreciated...thanks!
This will be due to how you have wired the transformer secondary to the AC/DC kit. You need to wire the 24vac (no centre tap connected) between 0v and one of the AC in to make the voltages you need.

It sounds like you have the the 24vac wired between the 2 x AC in with centre tap to 0v which will make the voltages you mention.

The ideal transformer would have been a 2 x 22vac wired as 44vac centre tapped wired to 0v and each 22vac end to a AC in each.

"JLM AC/DC Ver. 2 kit is a Linear based universal power supply which can generate 3 voltage rails from a single or dual 24 to 30vac."

Hi Joe. I didn't think the input voltage could be as high as 44vac? So, from the above statement you could input as much as 60vac into the acdc? 30+30?

I don't quite understand how the secondary setup translates to what dc voltage is output...

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Joe Malone
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Re: Acdc voltage issue

Post by Joe Malone »

desol wrote:
Joe Malone wrote:
desol wrote:Hi there

I have a version 2 or 3 ACDC. I want to use it to power a couple ADR scamp modules which require +/- 28vdc.

The acdc has been sitting in a drawer for a while. I powered it up today and for some reason i can only adjust the phantom voltage up to about 33vdc and the bipolar rails only up to around +/- 16vdc...but not any higher. I have a 30va toroid powering it...primaries in parallel, secondaries in series for 24vac.

Not sure what could be the problem here. Maybe one of the capacitors? Any help appreciated...thanks!
This will be due to how you have wired the transformer secondary to the AC/DC kit. You need to wire the 24vac (no centre tap connected) between 0v and one of the AC in to make the voltages you need.

It sounds like you have the the 24vac wired between the 2 x AC in with centre tap to 0v which will make the voltages you mention.

The ideal transformer would have been a 2 x 22vac wired as 44vac centre tapped wired to 0v and each 22vac end to a AC in each.
"JLM AC/DC Ver. 2 kit is a Linear based universal power supply which can generate 3 voltage rails from a single or dual 24 to 30vac."

Hi Joe. I didn't think the input voltage could be as high as 44vac? So, from the above statement you could input as much as 60vac into the acdc? 30+30?

I don't quite understand how the secondary setup translates to what dc voltage is output...
1 x 22vac to 25vac between the 0v and one AC in will work fine but the update to the capacitor bank will only we half wave 50 or 60Hz causing high ripple.

Using 2 out of phase 22vac windings both between 0v and both AC ins will give same unreg voltage but at full wave rectification of 100 or 120Hz so smoother unregulated dc voltages for the regulator to work with.

If you read the AC/DC Powerstation build thread and questions under that thread on this forum you will see this has question has been asked and answered many time there. Always best to use the online JLM calculator link on that thread to work out the best AC voltage input needed between 0v and one AC in which should be one secondary winding value. To do full wave you will need 2 secondary windings of the same value.
Joe :-)
JLM Audio
Capturing Audio without Injury

desol
Posts: 10
Joined: Mon Feb 22, 2010 7:36 am

Re: Acdc voltage issue

Post by desol »

Joe Malone wrote:
1 x 22vac to 25vac between the 0v and one AC in will work fine but the update to the capacitor bank will only we half wave 50 or 60Hz causing high ripple.

Using 2 out of phase 22vac windings both between 0v and both AC ins will give same unreg voltage but at full wave rectification of 100 or 120Hz so smoother unregulated dc voltages for the regulator to work with.

If you read the AC/DC Powerstation build thread and questions under that thread on this forum you will see this has question has been asked and answered many time there. Always best to use the online JLM calculator link on that thread to work out the best AC voltage input needed between 0v and one AC in which should be one secondary winding value. To do full wave you will need 2 secondary windings of the same value.

Ok. I'll look for that calculator...and that's good information.

I did some searching and reading on half wave vs full wave, and while understanding the basic pro's and cons...how does using one or the other affect noise or transient response in an audio circuit? ...and will half-wave increase heat at the transformer/rectifiers? I like to do things properly so, i'll get another transformer if need be.

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Joe Malone
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Re: Acdc voltage issue

Post by Joe Malone »

desol wrote:
Joe Malone wrote:
1 x 22vac to 25vac between the 0v and one AC in will work fine but the update to the capacitor bank will only we half wave 50 or 60Hz causing high ripple.

Using 2 out of phase 22vac windings both between 0v and both AC ins will give same unreg voltage but at full wave rectification of 100 or 120Hz so smoother unregulated dc voltages for the regulator to work with.

If you read the AC/DC Powerstation build thread and questions under that thread on this forum you will see this has question has been asked and answered many time there. Always best to use the online JLM calculator link on that thread to work out the best AC voltage input needed between 0v and one AC in which should be one secondary winding value. To do full wave you will need 2 secondary windings of the same value.

Ok. I'll look for that calculator...and that's good information.

I did some searching and reading on half wave vs full wave, and while understanding the basic pro's and cons...how does using one or the other affect noise or transient response in an audio circuit? ...and will half-wave increase heat at the transformer/rectifiers? I like to do things properly so, i'll get another transformer if need be.
I would get it all going with that transformer you have and if you have any hum or buzz issues then we would check out some voltages on the AC/DC PCB to see if it was transformer related or not.

I think for the low current load of the scamp modules the transformer you have will be fine.
Joe :-)
JLM Audio
Capturing Audio without Injury

desol
Posts: 10
Joined: Mon Feb 22, 2010 7:36 am

Re: Acdc voltage issue

Post by desol »

Thanks Joe.

I did test the ACDC briefly, and it worked like you said.

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