Bad Soundia Caps?

[jamesm113]

From an audiosource subwoofer built in 1999. Subwoofer is hums with no RCA line connected to it or when the receiver is off.

Is that stuff glue or busted caps?

Thanks!

[selldoor]

Re: Bad Soundia Caps?

Bad caps

[Rulycat]

Re: Bad Soundia Caps?

Looks related to Anodia caps..

[mariushm]

Re: Bad Soundia Caps?

Looks like they're right after the bridge rectifier, maybe used to create a split power supply.

It's possible there's quite some ripple from the transformer coming into the caps - replace them with a good brand capacitors (panasonic, nippon chemi con, nichicon) and consider replacing them with 35v rated ones, those will handle larger ripple better..

[kc8adu]

Re: Bad Soundia Caps?

that your hum right there.replace all of them.

[jamesm113]

Re: Bad Soundia Caps?

I replaced those 2 with 470uF 35V RadioShack ones (only ones i could get on short notice)

Hum is definitely improved, but still present. The other caps didn't look to have any issues

[selldoor]

Re: Bad Soundia Caps?

If your not going to follow the advice given, there is little point in our trying to help?

[jamesm113]

Re: Bad Soundia Caps?

I'm sorry, the only advice I saw last night before I replaced them was "Bad caps" so I replaced them.

Is the RadioShack brand bad? Should I replace the rest of the caps on the PCB even though they don't have signs of failure?

I've attached the schematic. I *think* I replaced C7 and C18

[mariushm]

Re: Bad Soundia Caps?

You mean c17 and c18 .. it's the two by the bridge rectifier D1.

Radioshack buys general purpose capacitors from various companies and rebrands them.
They're generally not suited for use in locations that are subjected to excess heat or ripple, or if they need to be low esr.

It may work now, but they may go bad sooner or later.

If you're going to buy a proper set, I recommend also changing the capacitors after the linear regulators , C15 and C16 ... both 100uF 16v. Replace them with 100uF 25v, preferrably Panasonic FC, FM, FR, Nichicon HM, Nippon Chemi Con KZE

The reason is mostly because those two ICs U5 and U6 are linear regulators, which means they take 14-16v and output stable +12v and -12v but the difference is dissipated as heat into the area around.

If those 100uF 16v are near the linear regulators, they would be constantly under heat from those ICs. Going to 25v is not required, as the capacitors will only see 12v on them, but usually capacitors rated for 25v are just a bit larger and more resistant to heat. From the pictures, it looks like you can fit slightly larger capacitors.

Check the badcaps online store, should find both these capacitor values+voltage ratings or use digikey.com / newark.com etc

[Pentium4]

Re: Bad Soundia Caps?

I don't know about yours but my local Radio Shack only has Lelon caps on hand, which are trash, so if they are those I'd buy some better ones like already suggested.

[jamesm113]

Re: Bad Soundia Caps?

Sorry for the delay, got a little sidetracked.

Anyway, I replaced C15 and C16 with 100uF 25V. Hum is still the same

[Agent24]

Re: Bad Soundia Caps?

Hum is definitely improved, but still present. The other caps didn't look to have any issues

They can go bad without visible symptoms.

What about C12 and C13 too? They look related to the power supply..

[jamesm113]

Re: Bad Soundia Caps?

Ok, I can try replacing those. Any others?

[mariushm]

Re: Bad Soundia Caps?

Check the ones that are close to the speaker output connectors - follow the leads from the connectors towards the insides and check those for capacity and resistance (if you don't have an esr meter)

Just on a rough and fast look I see there C8, c11, c14, c24... might as well replace c6 though it should cause issues...

I see mainly 4.7 uF 16v, 100uF 16v and 100uF 35v - you can replace all 100uF with 100uF 35v or 50v (if you get a better price for getting a 5 pack or 10 pack, you know what i mean), and it wouldn't hurt replacing the 4.7uF ones with higher voltage rating caps.

They're all small in capacity and cheap, all shouldn't be more than 3$ or so at digikey but for this one you can probably use the cheap radioshack capacitors if you don't want to spend a lot.

Without an ESR meter it's hard to pinpoint exact issues, or something to measure if the capacitors leak, letting DC go through to the speakers.

[lti]

Re: Bad Soundia Caps?

you can probably use the cheap radioshack capacitors if you don't want to spend a lot.

Radio Shack charges $1.49 for a 100uF cap.

[mariushm]

Re: Bad Soundia Caps?

Ouch! Wasn't aware of that.

I actually ordered today (among other stuff) 50 pcs x panasonic fm 100uf/25v from Farnell for 39.7 RON ... 11.5 dollars.

I don't know, probably the guy who invented Radioshack is rolling in his grave...

[jamesm113]

Re: Bad Soundia Caps?

These were the caps immediately next to the speaker leads (the red and black wires). Just ordered replacements for them + all those suggested above

[jamesm113]

Re: Bad Soundia Caps?

Well I replaced all the caps suggested and the two big ones pictured, and there is no improvement

[ben7]

Re: Bad Soundia Caps?

Well I replaced all the caps suggested and the two big ones pictured, and there is no improvement

Is it possible that you have a ground loop somewhere?

Is it buzzing with NO input wires connected?

Have you checked the rectifier diodes to see if they could be leaky?

[jamesm113]

Re: Bad Soundia Caps?

Is it possible that you have a ground loop somewhere?

Is it buzzing with NO input wires connected?

Have you checked the rectifier diodes to see if they could be leaky?

It's humming if the sub is the only thing plugged into the wall - no input wires connected at all