Power supply testing

AmpBuilder225 · 8th March 2009, 06:27 PM

Hi, I am building a guitar amp and was wondering if I can test functionality of the power supply without anything attached to it or will it need a load? The HT/B+ line it 480v to the power stage anodes if that's any help.

Thanks for any help!

AndrewT · 8th March 2009, 06:30 PM

Hi,
what would B+ rise to if no load is applied?

Is it a CRC type of PSU?
or an LCRC type?
The LCRC will rise to a very high B+, if there is no load.

Would that open circuit voltage be a problem for any of the capacitors?

AmpBuilder225 · 8th March 2009, 06:37 PM

Its an LCRC design but i'm not sure how to work out the voltage without a load. All my caps are ~600v and I have 4 el34's and 8 ecc83's. Do I work out the off-load voltage by looking at the currents drawn?

athos56 · 8th March 2009, 07:35 PM

I was told one time that it was ok to read the voltage right off the bare transformer leads, and that the unloaded voltage would be a bit higher than normal. I am using some unknown transfromers in a project, I know around what they put out, but not exactly. I planned on building the circuit up until the first RC section. So only the C-LC sections. Then I'll work out where I'm at voltage wise. I think it should be ok to power up the PSU for limited periods as long as your caps are over rated a bit.

AmpBuilder225 · 8th March 2009, 07:40 PM

Well my transformer HT is rated at 340V 0.8A under full ohmic load and 4.5% regulation and therefore 480V after a bridge rectifier. Should I expect around 550V or so off load do you think?

athos56 · 8th March 2009, 07:52 PM

While I'm inclined to think that you won't have to worry about your 600v caps, I'd leave the definitive answer to some of the wiser people here.

8th March 2009, 06:27 PM	#1
AmpBuilder225 diyAudio Member Join Date: Feb 2009	Power supply testing Hi, I am building a guitar amp and was wondering if I can test functionality of the power supply without anything attached to it or will it need a load? The HT/B+ line it 480v to the power stage anodes if that's any help. Thanks for any help!

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8th March 2009, 06:30 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, what would B+ rise to if no load is applied? Is it a CRC type of PSU? or an LCRC type? The LCRC will rise to a very high B+, if there is no load. Would that open circuit voltage be a problem for any of the capacitors?

8th March 2009, 06:37 PM	#3
AmpBuilder225 diyAudio Member Join Date: Feb 2009	Its an LCRC design but i'm not sure how to work out the voltage without a load. All my caps are ~600v and I have 4 el34's and 8 ecc83's. Do I work out the off-load voltage by looking at the currents drawn?

8th March 2009, 07:35 PM	#4
athos56 diyAudio Member Join Date: May 2006 Location: Yakima, Washington	I was told one time that it was ok to read the voltage right off the bare transformer leads, and that the unloaded voltage would be a bit higher than normal. I am using some unknown transfromers in a project, I know around what they put out, but not exactly. I planned on building the circuit up until the first RC section. So only the C-LC sections. Then I'll work out where I'm at voltage wise. I think it should be ok to power up the PSU for limited periods as long as your caps are over rated a bit.

8th March 2009, 07:40 PM	#5
AmpBuilder225 diyAudio Member Join Date: Feb 2009	Well my transformer HT is rated at 340V 0.8A under full ohmic load and 4.5% regulation and therefore 480V after a bridge rectifier. Should I expect around 550V or so off load do you think?

8th March 2009, 07:52 PM	#6
athos56 diyAudio Member Join Date: May 2006 Location: Yakima, Washington	While I'm inclined to think that you won't have to worry about your 600v caps, I'd leave the definitive answer to some of the wiser people here.