dodgy PSU capacitor - Page 2

DF96 · 2nd July 2011, 01:33 PM

"mf" is old American for microfarads? "15mF" (at 63V) is reasonably unambiguous, as 15uF would be too small for a smoother at low voltage but 15000uF would be plausible. Strictly speaking "15mf" means 1.5x10^-17, as it combines two prefixes with no units.

AndrewT · 2nd July 2011, 04:35 PM

mf is gobble de gook as you have pointed out.
MF is almost as bad in that it is (almost) incomprehensible.

DF96 · 2nd July 2011, 06:44 PM

15MF would be a very big capacitor!!

I don't know if you are old enough to remember the newspaper adverts for early tranny radios "2 bands, 5 transistors, 400MW output"!

Rogelio · 7th July 2011, 12:31 PM

I think bulging of capacitor was due heat created by voltage exceeding the working voltage of capacitor or high frequency current filtered by capacitor for a long period that result "oil" inside the capacitor to expand.

DF96 · 7th July 2011, 01:42 PM

No, unlikely on both counts. Andrew tells us that he was within the voltage rating. It was being used as a smoother so there would not be much high frequency current, but could be lots of low frequency current.

Pressure in an electrolytic cap is caused by gas, not the "oil" expanding.

Rogelio · 03:18 AM

If you noticed capacitor w/ bulging problem mostly happen with PWM or Power Supplies and motherboard connected to the pwm psu. This PWM circuit have 20khz high freq oscillator.

Analog Power Supply ( half wave 60 hz and 120 hz. ) also have this problem but it was due to defective regulator circuit or over voltage. Unlike with PC PSU having more bulging capacitor problem than analog psu.

"oil" or electrolyte inside the heated capacitor produced hydrogen gas.

2nd July 2011, 04:35 PM	#12
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	mf is gobble de gook as you have pointed out. MF is almost as bad in that it is (almost) incomprehensible. __________________ regards Andrew T.

8th July 2011, 02:53 AM	#16
Rogelio diyAudio Member Join Date: May 2011 Location: Quezon City	If you noticed capacitor w/ bulging problem mostly happen with PWM or Power Supplies and motherboard connected to the pwm psu. This PWM circuit have 20khz high freq oscillator. Analog Power Supply ( half wave 60 hz and 120 hz. ) also have this problem but it was due to defective regulator circuit or over voltage. Unlike with PC PSU having more bulging capacitor problem than analog psu. "oil" or electrolyte inside the heated capacitor produced hydrogen gas. Last edited by Rogelio; 8th July 2011 at 03:18 AM.

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2nd July 2011, 01:33 PM	#11
DF96 diyAudio Member Join Date: May 2007	"mf" is old American for microfarads? "15mF" (at 63V) is reasonably unambiguous, as 15uF would be too small for a smoother at low voltage but 15000uF would be plausible. Strictly speaking "15mf" means 1.5x10^-17, as it combines two prefixes with no units.

2nd July 2011, 06:44 PM	#13
DF96 diyAudio Member Join Date: May 2007	15MF would be a very big capacitor!! I don't know if you are old enough to remember the newspaper adverts for early tranny radios "2 bands, 5 transistors, 400MW output"!

7th July 2011, 12:31 PM	#14
Rogelio diyAudio Member Join Date: May 2011 Location: Quezon City	I think bulging of capacitor was due heat created by voltage exceeding the working voltage of capacitor or high frequency current filtered by capacitor for a long period that result "oil" inside the capacitor to expand.

7th July 2011, 01:42 PM	#15
DF96 diyAudio Member Join Date: May 2007	No, unlikely on both counts. Andrew tells us that he was within the voltage rating. It was being used as a smoother so there would not be much high frequency current, but could be lots of low frequency current. Pressure in an electrolytic cap is caused by gas, not the "oil" expanding.

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