powersupply not sure what to do?

prorms · 13th November 2006, 09:04 PM

every time i hook the filter caps my amperage go very high
when i dont have them hook up seems to only draw what power amp needs iam realy stuck what to do?

BobEllis · 13th November 2006, 09:15 PM

Are you sure that you connected the caps with the proper polarity? (positive to positive and negative to negative) Connecting once the wrong way around may damage them, so it's best to replace rather than risk exploding caps.

Try a 100R 1W resistor between the bridge and each cap. That will limit the current to sensible values if there is a mistake. If the resistor burns, you have a problem. Be sure to bleed off the caps through a resistor before hooking up the amp again.

prorms · 14th November 2006, 01:09 AM

have them connect postive to postive negitive to negitive
100 ohms between the two on each side no burn
but iam not sure on what size cap to use???

BobEllis · 14th November 2006, 01:39 AM

I've drawn pictures like that and blown up caps because reality wasn't like the sketch.

If you are shooting for 35V rails, use 50V caps. Your amp will determine how much capacitance you need. A rule of thumb for class AB amps is 10,000 uF or more on each rail for each 100 watts of output. Class A amps are going to need a lot more - think at least 100,000 uf

Edit: yes, that's where the resistors go.

13th November 2006, 09:04 PM	#1
prorms diyAudio Member Join Date: Nov 2006	powersupply not sure what to do? every time i hook the filter caps my amperage go very high when i dont have them hook up seems to only draw what power amp needs iam realy stuck what to do?

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13th November 2006, 09:15 PM	#2
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	Are you sure that you connected the caps with the proper polarity? (positive to positive and negative to negative) Connecting once the wrong way around may damage them, so it's best to replace rather than risk exploding caps. Try a 100R 1W resistor between the bridge and each cap. That will limit the current to sensible values if there is a mistake. If the resistor burns, you have a problem. Be sure to bleed off the caps through a resistor before hooking up the amp again.

14th November 2006, 01:39 AM	#4
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	I've drawn pictures like that and blown up caps because reality wasn't like the sketch. If you are shooting for 35V rails, use 50V caps. Your amp will determine how much capacitance you need. A rule of thumb for class AB amps is 10,000 uF or more on each rail for each 100 watts of output. Class A amps are going to need a lot more - think at least 100,000 uf Edit: yes, that's where the resistors go.

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