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Old 29th March 2012, 09:07 AM   #1231
AndrewT is offline AndrewT  Scotland
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I would accept the warranty from the manufacturer.

If they say 50V working, then I expect it to survive for at least the lifetime and in specification for all voltages up to and including 50.00V

If my electricity supplier exceeds the stated 254Vac and I can prove that the overvoltage damaged my equipment, then the power supply company pays.
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Old 29th March 2012, 01:31 PM   #1232
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You have to watch the no-load peak voltage on the PS caps. Does the amp provide a load immediately on turn on? Or some number of mS later? I would prefer to have caps rated a whole lot higher than 10% over the expected rail voltage.

_-_-bear
no need. if there is a voltages peak at turn on, there is no problem. 50V caps can withstand peaks up to maybe 60V and the differnce from no load to loaded is about 2V. if it is much more, your transformer is way to smal.
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Old 29th March 2012, 03:19 PM   #1233
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Sure... Andrew, you go ahead and "prove" it. Go ahead and try to collect. Ha ha.

AudioSan, the caps may well withstand peak voltages far in excess of what the label on the cap says. But I am here to tell you that the number one component that fails in most electronic gear, other than due to damages as the result of things like shorted outputs and other abuses is failures of capacitors.

I would NEVER use a cap rated at 50 volts working within 25% of the rated voltage in a POWER SUPPLY application like this. Never. You may, I would not. Sure it will likely work, and if you use high quality caps that also are actually able to handle a bunch more voltage and are conservatively rated and well built, intended to be used in circuits where there are stresses applied, they will work fine. But as a design rule, not for me thanks.

If I had an amp with a 40-49vdc rail, I would use a cap rated at 75wvdc at minimum. Not 50wvdc.

Ymmv. Mine is pretty stable on this.

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Old 29th March 2012, 03:55 PM   #1234
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Originally Posted by bear View Post
Sure... Andrew, you go ahead and "prove" it. Go ahead and try to collect. Ha ha.

AudioSan, the caps may well withstand peak voltages far in excess of what the label on the cap says. But I am here to tell you that the number one component that fails in most electronic gear, other than due to damages as the result of things like shorted outputs and other abuses is failures of capacitors.

I would NEVER use a cap rated at 50 volts working within 25% of the rated voltage in a POWER SUPPLY application like this. Never. You may, I would not. Sure it will likely work, and if you use high quality caps that also are actually able to handle a bunch more voltage and are conservatively rated and well built, intended to be used in circuits where there are stresses applied, they will work fine. But as a design rule, not for me thanks.

If I had an amp with a 40-49vdc rail, I would use a cap rated at 75wvdc at minimum. Not 50wvdc.

Ymmv. Mine is pretty stable on this.

_-_-bear
yes. ofcourse they are the number one.
thats becouse they dry out. couse for this is heat. they have a lifetime. only other component that has a lifetime is the transistors. about twice the lifetime. so caps will b the first to fail in any amp. this one or that one, or what ever one.
and 75V caps on 49V supply? why not 63V caps?
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Old 29th March 2012, 04:45 PM   #1235
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Quote:
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You have to watch the no-load peak voltage on the PS caps. Does the amp provide a load immediately on turn on? Or some number of mS later?
How many mS to fully charge the power supply capacitor bank ?
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Old 29th March 2012, 05:29 PM   #1236
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and most also use some sort of softstart, so voltages peak on turn on will brobably not happen.

Last edited by AudioSan; 29th March 2012 at 05:35 PM.
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Old 29th March 2012, 05:33 PM   #1237
AndrewT is offline AndrewT  Scotland
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Theoretically the PSU never reaches fully charged.
But if you will settle for 99% of the theoretical fully charged or 99.5% of the theoretical fully charged then you can define the charge time in RC * factor, or in cycles of mains waveform, or ms if you desire.
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Old 29th March 2012, 10:19 PM   #1238
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So you guys think it's better to put 49V at 50V@105c rated caps then 49V at 63V@85c rated caps?
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Old 29th March 2012, 10:27 PM   #1239
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the best will be 63V 105c caps.
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Old 29th March 2012, 11:49 PM   #1240
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the best will be 63V 105c caps.
These won't fit - 35mm
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