Subwoofer Power Supply Problem

[atari]

I purchased the subwoofer 'Rocket ULW-10' around 2005 and recently was experiencing a humming noise coming from the sub. So I researched the problem on the internet and it was suggested on various forums that this could be a capacitor issue.

After checking the audio source and for grounding issues, I then decided to open up the subwoofer plate amplifier. What I discovered was that 2 of the capacitors on the power supply board were blown.

The 2 capacitors had the following specifications:
'PEC' or 'REC' , SR , 1000uF , 25V , 85C

Now I am assuming from looking at the power supply that it is a linear design and not switch mode design.

What would be a good replacement for these capacitors ?

[jpdoe]

Here's the datasheet, for someone more experienced than me on finding replacements.

[atari]

I had searched the internet and could not find any information on the capacitors. When I called technical support at Onix (subwoofer manufacturer), they did not know either and did not have the service manual since the sub was discontinued.

So, thanks jpdoe for finding this information on the REC capacitors for me. I see in the data sheet that ripple current for my capacitors is 925mA, however it does not state what the esr values are for the capacitors. Should I be looking for low esr capacitors ?

The subwoofer is a sealed design (non ported). Also, the plate amp does not have any vents, it fits inside the sub's cabinet in a sealed hard plastic box, isolating it from the speaker. Now I am concerned about the heat build up and I would like to know if its safe to stay with a 85C capacitor ?

These are the electronic retailers that I will be using to purchase the replacement caps

http://ca.mouser.com/search/Default.aspx
http://dkc1.digikey.com/ca/digihome.html
http://www.e-sonic.com/acc/home.aspx

[Toasty]

As these were General Purpose, low ESR won't hurt. You just don't have to go crazy and get super low.

Go with 105°C caps. I'd also replace the other 4 small caps on that board.

Find someway to ventilate the space to the outside, even if it is by convection.

[Logistics]

I usually suggest Panasonic FM's from Digi-Key, but I think someone said the FC's, while not as low ESR nor high ripple, are made in a fashion that they withstand heat better than the FM's or last longer, something like that.

[PCBONEZ]

You heard someone spewing wha about aqueous vs non-aqueous.
- That's all it is is -> wha (rubbish).

If you used an 'otherwise the same' electrolyte the difference between aqueous vs non-aqueous would be a valid point for comparison,,,
- but they don't use an 'otherwise the same' electrolyte.

I don't remember ever seeing or hearing of a blown panny FM. - Ever.
.

[Toasty]

Here:

http://search.digikey.com/scripts/Dk...name=P12379-ND

Panasonic FM 105°C - 12.5 x 20 mm - Ripple= 2600ma - ESR=.018 ohms - $1.03 each

[Logistics]

Originally Posted by PCBONEZ

You heard someone spewing wha about aqueous vs non-aqueous.
- That's all it is is -> wha (rubbish).

If you used an 'otherwise the same' electrolyte the difference between aqueous vs non-aqueous would be a valid point for comparison,,,
- but they don't use an 'otherwise the same' electrolyte.

I don't remember ever seeing or hearing of a blown panny FM. - Ever.
.

That's good to know because I still use the FM, regardless.

I've never seen a blown Panny FM, either. If I ever see the thread where a user was going on about this, I'll reference it.

[atari]

I am hoping that I will get an improvement in either the power or sound quality. Can you guys tell me which side the filter capacitors are on that I am replacing - primary or secondary. In a SMPS, I know the primary is connected to the AC power and secondary is next to ATX connectors, but on this linear PSU circuit it is not clear.

Now, if I replace the 85C caps with 105C caps then I should not need to make any holes for ventilation. As for the digikey link that toasty sent, the size of the capacitor has to be 10mm in diameter, the panasonic FM capacitors are 12.5mm.

Today, I searched digikey and mouser and these are the capacitors that I found that were above the original capacitor specifications.

REC , SR , 1000uF , 25V , 85C , 925mA , 10x20mm
-----------------------------------------------------------------------------------------------
1. Nichicon UPW1E102MPD6 (1000uF , 25V , 105C , 1815mA)
2. Nichicon UHE1E102MPD (1000uF , 25V , 105C , 1910mA)
3. Chemicon ELXZ250ELL470MEB5D (1000uF , 25V , 105C , 1690mA)

Also, would I get an increase in amplifier performance if i replaced all the capacitors except the 2 large caps in the PSU with capacitors of a higher capacitance and ripple value ?

[PCBONEZ]

Any of your selections are good.
There is also an FC that matches PW exactly. (EEUFC1E102L)
My choice for an unvented PSU would be the PW or the FC.

It depends on what you mean by 'performance'.
You aren't going to get more power by replacing filter caps but you just might get rid of that AC hum.
By cleaning up the power you might also be able to 'crank it' a little more before the quality goes to crud.

.

[Toasty]

Chemicon correct # = ELXZ250ELL102MJ30S ( 565-1961-ND )

You've got a 47µF one there.

So how's yer eyes after them datasheets?
Wanna shoot 'em like marbles??

You can't fit 2.5mm more of cap in there for better ESR and 700-900mA more ripple?

[atari]

I looked at the PSU board again and the other 4 small capacitors are all 85c made by TREC - Transcend Electrolytic(Shenzhen)Co.,Ltd.

(2X) REC , SR , 47uF , 16V , 85C , 124mA , 5x11mm
(2X) REC , SR , 470uF , 16V , 85C , 440mA , 8x12mm
(2X) REC , SR , 1000uF , 25V , 85C , 925mA , 10x20mm

It was late at night when I went through all the data sheets and I was looking for replacements for all the other caps listed above. Those data sheets can make you go crazy with all those rows and columns, thanks for catching the error.

I think I will replace all 6 capacitors on the PSU board since they are all 85C. The PW series that pcbonez suggested looks good, and hopefully they will last much longer than the orginal chinese caps.

Thanks guys for all your help.

[Logistics]

Originally Posted by atari

I am hoping that I will get an improvement in either the power or sound quality. Can you guys tell me which side the filter capacitors are on that I am replacing - primary or secondary. In a SMPS, I know the primary is connected to the AC power and secondary is next to ATX connectors, but on this linear PSU circuit it is not clear.

Also, would I get an increase in amplifier performance if i replaced all the capacitors except the 2 large caps in the PSU with capacitors of a higher capacitance and ripple value ?

Amplifiers used with subwoofers or large woofers can always benefit from proper capacitance in the filter-capacitor stage because it helps them deliver all that bass, but the impedance and speed of said capacitors is also important. (Let's just say, "The quality of said capacitors is important!") As a general rule 0.1F (that's .1 Farads, not microfarads) is suggested for every 100W. Perhaps, it would be better to say that it's used as a general rule with over-built amplifiers.

Obviously, Onix did not decide to include 350,000uF of capacitance in your Rocket sub. You did not include pictures which would allow us to see the filter caps on the DC side, but I can't imagine anything more than two or three 10,000uF caps, if that, but the amplifier is also probably not based around hardware which would utilize the sort of current to be a really bangin' amp since it's a plate-amp and there is NO room for the kind of heat-sinking a high-current amp would need.

tl:dr If it was my amplifier, I would simply upgrade the unit to premium capacitors, but not change the capacitance. The main caps on the AC side, I would change to something with very high ripple; if possible a Panasonic TSED from Digi-Key or others in the TS series if the ED is too large.

[PCBONEZ]

Yes but this is the power supply to the amp. - Not the amp.

[Logistics]

Power stage is the only area I know of that uses filter caps/stiffening caps. I wasn't talking about decoupling caps or SVR caps. ?_? wut j00 tawkin' bout willis?

[Toasty]

>>You did not include pictures which would allow us to see the filter caps on the DC side<<

??

Now I'm confused...

>>The main caps on the AC side, I would change to something with very high ripple<<

This is a Linear PSU, is it not?

[atari]

I just finished replacing all 6 capacitors on the PSU circuit board. All TREC caps were changed to Nichicon caps. The only problem encountered, was that the solder pump could not fit to clear the some of the capacitor holes, so I had to use the method suggested on this site of using a steel needle.

The picture of the power supply shows which capacitors were changed, all 6 are circled. The capacitors with red circles were the blown caps, the caps with red and blue circles were fine.

After testing the subwoofer for 2 hours with music, it is clear that the background hum is completely gone. Now the bass sounded good even when the volume was cranked to 3/4 on the dial, however it is hard to say whether the new capacitors with higher ripple current made a difference. The other thing I noticed with the subwoofer after 2 hours was that the plate amp shown in the photo was extremely warm to the touch.

[Logistics]

Originally Posted by Toasty

>>You did not include pictures which would allow us to see the filter caps on the DC side<<

??

Now I'm confused...

>>The main caps on the AC side, I would change to something with very high ripple<<

This is a Linear PSU, is it not?

Sorry, what I meant by the "DC side" was the portion containing the main amplifier IC. And the "AC side" I just meant the stage where the large 2200uF filter caps were; before DC gets very much reduced for use with the amplifiers main IC.

[Rob]

Originally Posted by atari

The other thing I noticed with the subwoofer after 2 hours was that the plate amp shown in the photo was extremely warm to the touch.

The amp will get warm to the touch because it is conducting heat through the plate. Since it is a sealed unit, that plate also helps dissipate the heat.

Since you are using 105c low ESR caps, they should not blow because if overheating issues like the 85c have blown. I have a Yamaha sub that does the same thing. It should only heat up when you are playing music and pushing watts out of the sub.

[Dante]

This is an amazing forum. I had exactly the same symptoms that “atari” had – a humming AV123 Onix Rocket ULW-10 subwoofwer. A Google search got me here right away . I had first called tech support at AV123 which was a waste of time. They apparently take no responsibility for their product failures. After finding the needed parts here I ordered a double set of the caps from Digikey, paid $9 including shipping and got them just a few days later. I put them in the same evening and I have a working speaker again.

Looking at the extremely low cost of quality capacitors, it blows my mind that a manufacturer decides to cut corners and put substandard components in a product like this. The retail price for the subwoofer is high enough and there simply aren’t enough caps in this product that it can add up to enhanced profits. Looks more like planned obsolescence to me.

Anyway, thanks again guys!