Power supply capacitor tolerances

On Sun, 2 Sep 2012, Josh Dersch wrote: What are the dimensions of the original capacitor (in millimeters)? If it is being used at 5V then you could go down slightly on the voltage rating, but I'm not sure I'd want to go up much higher because an even larger plate surface will result in an even thinner oxide layer being formed, which isn't optimal for electrolytics. The general rule of thumb in an application such as this is to use a capacitor that is rated for 2x the operating voltage. As far as the capacitance goes, you can probably go a little higher without too much worry (20% of 16,000uF is 3,200uF, so the original could have been 19,200uF and still would have been within specs), but I'd keep it under about 18,000-22,000 unless you know for certain that the existing regulator(s) and/or reverse biased protection diode can handle it (you don't want to burn out your regulator when you switch the supply off and the capacitor still has a charge). Axial style capacitors are available in that range, but you may not like the price. They appear to be going for USD ~$10.00-15.00 each in qty of about 50/pcs. There are a number of capacitors in Nichicon's VX series that you could consider. The VX series are general purpose 85c rated parts. TVX1C153MDD 16V 15000uF 22x52mm TVX1A153MDD 10V 15000uF 22x40mm TVX1C223MDD 16V 22000uF 25.4x61mm TVX1A223MDD 10V 22000uF 22x52mm Another option worth considering is using a radial mount part. Just attach it to the board with some silicone (which isn't a bad idea for large capacitors anyway) and extend and insulate one of the leads with some small teflon tubing. The Nichicon VY and VZ are 105c rated, and the VK and VR are 85c rated. UVY1C153MHD 16V 15000uF 18x40mm UVY1A153MHD 10V 15000uF 16x35.5mm UVY1C223MRD 16V 22000uF 22x40mm UVY1A223MHD 10V 22000uF 18x40mm UVZ1C153MRD 16V 15000uF 20x40mm UVZ1A153MHD 10V 15000uF 18x35.5mm UVZ1C223MRD 16V 22000uF 22x50mm UVZ1A223MRD 10V 22000uF 20x40mm UVK1C153MHD 16V 15000uF 18x40mm UVK1A153MHD 10V 15000uF 16x35.5mm UVK1C223MRD 16V 22000uF 22x40mm UVK1A223MHD 10V 22000uF 18x40mm UVR1C153MRD 16V 15000uF 20x40mm UVR1C153MRD6 16V 15000uF 25x30mm UVR1A153MHD 10V 15000uF 18x35.5mm UVR1C223MRD 16V 22000uF 22x50mm UVR1C223MRD6 16V 22000uF 25x40mm UVR1A223MRD 10V 22000uF 20x40mm UVR1A223MRD6 10V 22000uF 25x30mm I might also consider using a Nichicon HE, PW, or PS series assuming I could find a close value (these generally top out at 10,000uF or 15,000uF). These are rated for high ripple and 105c. I use tons of these in all sorts of values in switching power supplies of all sizes and they would probably work just fine in a linear supply too. UPW1A153MHD 10V 15000uF 18x40mm UPS1A153MHD 10V 15000uF 18x40mm http://nichicon-us.com/english/products/pdfs/e-vx.pdf http://nichicon-us.com/english/products/pdfs/e-vy.pdf http://nichicon-us.com/english/products/pdfs/e-vz.pdf http://nichicon-us.com/english/products/pdfs/e-vk.pdf http://nichicon-us.com/english/products/pdfs/e-vr.pdf http://nichicon-us.com/english/products/pdfs/e-he.pdf http://nichicon-us.com/english/products/pdfs/e-pw.pdf http://nichicon-us.com/english/products/pdfs/e-ps.pdf