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Hello, If individual caps were used on the screens and PI rather than the series arrangement what would the values be? I'm trying get around having to order a 220uf. Thank you for any help.
series caps on screens and PI
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Stevem
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Re: series caps on screens and PI
A single 600 volt cap in the uf you need it in is more expensive than two good 220uf at 350 volt caps and besides that than that 50 uf cap needs to be made larger also!
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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gingertube
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Re: series caps on screens and PI
Andrew,
I would seriously recommend some minor changes to that circuit.
The voltage is being shared betwen that 220uF on the bottom and the 50uF + the second 50uF in parallel on the top.
A quick and dirty analysis:
Assume:
Top cap is 50uF + 50uF = 100uF
Bottom cap is 220uF.
500V across the series connected caps.
these caps have the same chrage current running through them so they charge to a voltage determined by their capacitance.
So the 50uF + 50uF will have 343.7 V across them
The 220uF will have 156V across it.
Actually the 1K to teh second 50uF will throw this off a bit which will result in even more voltage across the first 50uF almost ceratinly more than its 350V rating.
The 2 x 220K voltage share resistors are doing very little to "restore" the voltage balance.
Its a bad design.
Cheers,
Ian
I would seriously recommend some minor changes to that circuit.
The voltage is being shared betwen that 220uF on the bottom and the 50uF + the second 50uF in parallel on the top.
A quick and dirty analysis:
Assume:
Top cap is 50uF + 50uF = 100uF
Bottom cap is 220uF.
500V across the series connected caps.
these caps have the same chrage current running through them so they charge to a voltage determined by their capacitance.
So the 50uF + 50uF will have 343.7 V across them
The 220uF will have 156V across it.
Actually the 1K to teh second 50uF will throw this off a bit which will result in even more voltage across the first 50uF almost ceratinly more than its 350V rating.
The 2 x 220K voltage share resistors are doing very little to "restore" the voltage balance.
Its a bad design.
Cheers,
Ian
Re: series caps on screens and PI
I am using a 300-0-300 PT so I don't need the common 220uf to help with the voltage handling but when used in series with the two separate 50uf caps what capacitance is each node getting? If it is near 50uf for each node I will just take the 220uf out. I did notice that when I turn the amp off it is quiet for a few seconds then an ugly hum for another few seconds then it fades out. Thanks for the advice.
Re: series caps on screens and PI
Hi andrew, Since you are using a 300-0-300 Pt you dont need the series connected caps a single 500V 100 uf will work fine. Your B+ will be around 440V instead of 500+ .
Connect those 500V 50uf caps in parallel not series to give you 100uf with voltage rating = 500V
Caps in series add voltage ratings caps in parallel add capacitance but if the voltage ratings are equal the voltage rating remains unchanged.
So, 2 350V caps in series gives 700V. Capacitance divides so 220/2=110uf. A 100uf cap will work fine, you could go as low as 50uf with no problems but will hear more noise due to less filtering.Hope this helps.
Connect those 500V 50uf caps in parallel not series to give you 100uf with voltage rating = 500V
Caps in series add voltage ratings caps in parallel add capacitance but if the voltage ratings are equal the voltage rating remains unchanged.
So, 2 350V caps in series gives 700V. Capacitance divides so 220/2=110uf. A 100uf cap will work fine, you could go as low as 50uf with no problems but will hear more noise due to less filtering.Hope this helps.