are "super pup" caps any good?

mpmarino · 8th September 2005, 10:12 PM

A local guy has a small box of CDE 'super pups'. They are 2uf__ 200vdc__ #MPY 2w2. Are they worth grabbing for $0.25 us each or so? What are they made of?? They have a paper outer cylinder but what's inside.??

Thanks in advance..
Marc

Sch3mat1c · 8th September 2005, 11:11 PM

Probably leaky paper caps. They tend to absorb moisture.

You can check them with a DC supply more than 80V and a neon light. Connect the neon in series with the capacitor and connect up the power. The neon will blink once as the capacitor charges to somewhere around +V, minus 10 to 60V (depending on the neon light and amount of current pulsed). If it blinks at all within thirty seconds, the cap is leaky and should be discarded. (At 1uF and around +120VDC, this represents 30Mohm. 100V across such a leakage followed by a 220k will put 0.7V on the output, a generous portion of an audio signal.)

Tim

Sch3mat1c · 9th September 2005, 12:11 AM

FWIW, if you can measure the peak voltages in such a circuit, the exact formula for determining average leakage resistance is:

R = t / [C * ln (Vs-Voff / Vs-Von)]

Where R is the effective leakage resistance, C is the capacitance in farads, t is time between blinks in seconds, Vs is supply voltage, Von is the turn-on (highest peak) voltage of the neon and Voff is the minimum (lowest peak) voltage of the neon, when it turns off.

The natural log comes from taking the inverse of the RC exponential curve.

Typical values I would expect:
Vs = 200V, Von = 80V, Voff = 40V, C = 0.1uF (0.0000001 F), t = 60s, R = 2 x 10^9 ohms (2 gigaohms).

At that rate, some careful watching of a VOM should give accurate enough voltages for high precision with this formula.

Oh, and if you aren't using those caps for much DC, or very slow AC (low frequency oscillator for example), the leakage won't matter much. They'd probably be great for speakers.

Tim

mpmarino · 10th September 2005, 04:02 PM

Thanks ..

Any opinion on thier use as a cap in the signal path... as in a preamp etc. I didn't have in mind DC use.

Sch3mat1c · 12th September 2005, 08:12 PM

Well there are only three things a preamp would want with a cap of that size, coupling, bypass or tuning a bass filter. Only the bass filter probably has no issues with leakage. The others depend.

If you mean like, how they sound, yeesh...

Tim

mpmarino · 13th September 2005, 01:14 AM

Quote:

If you mean like, how they sound, yeesh...

well then..I guess I won't buy any more! Thanks for yer input!

8th September 2005, 10:12 PM	#1
mpmarino diyAudio Member Join Date: Jun 2004 Location: Crunchville, where I don't fit in.	are "super pup" caps any good? A local guy has a small box of CDE 'super pups'. They are 2uf__ 200vdc__ #MPY 2w2. Are they worth grabbing for $0.25 us each or so? What are they made of?? They have a paper outer cylinder but what's inside.?? Thanks in advance.. Marc __________________ Crazy Yankee.

8th September 2005, 11:11 PM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Probably leaky paper caps. They tend to absorb moisture. You can check them with a DC supply more than 80V and a neon light. Connect the neon in series with the capacitor and connect up the power. The neon will blink once as the capacitor charges to somewhere around +V, minus 10 to 60V (depending on the neon light and amount of current pulsed). If it blinks at all within thirty seconds, the cap is leaky and should be discarded. (At 1uF and around +120VDC, this represents 30Mohm. 100V across such a leakage followed by a 220k will put 0.7V on the output, a generous portion of an audio signal.) Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

9th September 2005, 12:11 AM	#3
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	FWIW, if you can measure the peak voltages in such a circuit, the exact formula for determining average leakage resistance is: R = t / [C * ln (Vs-Voff / Vs-Von)] Where R is the effective leakage resistance, C is the capacitance in farads, t is time between blinks in seconds, Vs is supply voltage, Von is the turn-on (highest peak) voltage of the neon and Voff is the minimum (lowest peak) voltage of the neon, when it turns off. The natural log comes from taking the inverse of the RC exponential curve. Typical values I would expect: Vs = 200V, Von = 80V, Voff = 40V, C = 0.1uF (0.0000001 F), t = 60s, R = 2 x 10^9 ohms (2 gigaohms). At that rate, some careful watching of a VOM should give accurate enough voltages for high precision with this formula. Oh, and if you aren't using those caps for much DC, or very slow AC (low frequency oscillator for example), the leakage won't matter much. They'd probably be great for speakers. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

10th September 2005, 04:02 PM	#4
mpmarino diyAudio Member Join Date: Jun 2004 Location: Crunchville, where I don't fit in.	Thanks .. Any opinion on thier use as a cap in the signal path... as in a preamp etc. I didn't have in mind DC use. __________________ Crazy Yankee.

12th September 2005, 08:12 PM	#5
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Well there are only three things a preamp would want with a cap of that size, coupling, bypass or tuning a bass filter. Only the bass filter probably has no issues with leakage. The others depend. If you mean like, how they sound, yeesh... Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
What makes Nichicon "muse"/"for audio" caps different ?	percy	Parts	2	3rd October 2009 05:53 PM
Peavey "Super Festival" VTA-400 - upgrading to 400W?	pharaohamps	Tubes / Valves	11	22nd March 2009 12:25 PM
Linear voltage regulator: how to make good use of "sense" and "ground sense"?	NeoY2k	Analog Line Level	7	6th September 2008 11:35 PM
Super Sanken Final Stage "Tauro"	Stee	Solid State	25	19th March 2008 08:01 PM
Audio Crafters Guild "Super Symmetric Power Supply"	raincheck	Digital Source	16	22nd April 2002 08:06 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read