Which capacitors for Subwoofer amplifier power supply?

[mysterfxit]

I have a KLH ASW10-120 powered subwoofer that died on me. Upon opening I can see the two big capacitors on the power supply board have leaked.

The markings on the capacitors only say 6800uf, 50V, vent+105º, vented. Reading around (this forum and others) everyone has their recommendations for brands/series of capacitors, but the only one that turns up at mouser for these specs is the Nichicon UVZ1H682MRD.

I'd like to replace them with quality/upgraded parts. They also have a 63V version, would this be less prone to failure?

Any advice will be appreciated.

[TheLaw]

Re: Which capacitors for Subwoofer amplifier power supply?

Hi,

Those capacitors are used to smooth out unfiltered DC. You can go as far up in voltage as you want, just make sure it fits. Can you please measure the diameter of the capacitor? And how tall can it be before it hits that AC transformer?

What is all that black stuff on the board around the resistors/wire socket? Is that the leaked electrolyte from the capacitor? That stuff is electrically conductive so hopefully it didn't short out anything else on the board. It just seems odd that the black "burn" marks are around all of those components. Check the bottom of the board and see if anything looks wrong there, also. If they look toasted to you, or you just want to be safe, you can replace the resistors as well. Usually resistors can tolerate shorts alright, but if they look burnt out, replace em.

I can't tell completely but...

Resistor 1: 10-11ohm
Resistor 2: 22ohm
Resistor 3: 22ohm

You are right. There aren't many options for 6800uF @ 50V on Mouser. 6800uF is a standard value, but I have noticed that it isn't used as often. The VY/VZ are definitley an uprade from that piece of crap "D.S" capacitor. I have never heard of "D.S" capacitor in my life...Such nerve these people have to use such junk.

Now, I don't want to get yelled at, but usually, for filter caps like that, it's alright to go up in capacitance as well. However, you shouldn't go up too much because inrush current could be too much for your rectifier to handle.


So the VZ/Vy should be a good fit...as long as it fits.

[mysterfxit]

Re: Which capacitors for Subwoofer amplifier power supply?

Thank you so much for your reply!

I believe the current capacitors are about 30x50mm. The 50V nichicon is 22x50 and the 63V is 25x50.

Yes, I'm pretty sure that burned stuff is electrolyte as it flakes off if disturbed. I didn't realize it's conductive, but now I'll be sure to clean it before I start working.

I'm an amateur (obviously) and I spent way more time than I care to admit trying to read those resistors. They all look like 5 variations of brown to me. I'm pretty sure I was way off.

[TheLaw]

Re: Which capacitors for Subwoofer amplifier power supply?

Thank you so much for your reply!

I believe the current capacitors are about 30x50mm. The 50V nichicon is 22x50 and the 63V is 25x50.

Yes, I'm pretty sure that burned stuff is electrolyte as it flakes off if disturbed. I didn't realize it's conductive, but now I'll be sure to clean it before I start working.

I'm an amateur (obviously) and I spent way more time than I care to admit trying to read those resistors. They all look like 5 variations of brown to me. I'm pretty sure I was way off.

Well to be truthful, DON'T take my word on the resistors. I can't see them very well myself. But I can assure you that the 4th band is gold which is different than brown. If you have a multimeter, you can just test them...

However, the resistors are probably fine. They are high(ish) wattage, so they can probably soak up a hit or two.

I'd recommend getting the 63V in that case, or even a 80/100V if it exists. Highest voltage you can get while it still fits is a rule of thumb. Even if you just got 50V, it won't fail. You might be aware but Nichicons are very good quality, and won't fail on you. Even if they are overvolted, they'll probably keep working. Good stuff.

You may want to look into those other crap capacitors over to the left, as they are almost bound to fail as well...but your call.

[mysterfxit]

Re: Which capacitors for Subwoofer amplifier power supply?

I've been busy at work and haven't had much time this week, but I got back into this and I think I will replace all the capacitors on this board while I'm at it.

I found all the others at Mouser except the ones on the left side of the second picture. I think they both are 2.2uf 50V -40-105º NP

I'm looking in the aluminum electrolytic, but nothing is turning up for NP. Can this be replaced with another type of capacitor?

Also, I'm not having an easy time removing the dried electrolyte form the board. I'm using alcohol and cotton swabs. The alcohol isn't helping anything. Is there any other solvent I can try?

Thank you.

[Scenic]

Re: Which capacitors for Subwoofer amplifier power supply?

if NP stands for non-polar (ie: no negative marking on the cap sleeve ; i can't tell from those pics), it's the same as bipolar.

http://www2.mouser.com/ProductDetail...qbTysnqlOGU%3d

[mysterfxit]

Re: Which capacitors for Subwoofer amplifier power supply?

Thank you. I don't know why I didn't see that.

Of course, now the two big caps are backordered.