Quad L-ite Sub (wharfedale sw-300) rustling - diyAudio
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Old 19th July 2013, 10:53 PM   #1
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Default Quad L-ite Sub (wharfedale sw-300) rustling

My Quad sub has started playing up.

We actually thought our next door neighbor fell down the stairs when it failed!

The sub started thumping itself and now makes loud rustling sounds.

I've taken the amp PCB out and I'm going to check the Capacitors in case they have dried out and also check / re-flow the soldering.

Any hints or tips on where else to look?

Thanks

Graeme
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Old 20th July 2013, 02:52 AM   #2
CBS240 is offline CBS240  United States
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Broken solder joint somewhere? Maybe around the input stage or feedback loop area? I imagine being joined to the constant vibration, the PCB ought to be built to be robust. But then agian, ......

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Old 20th July 2013, 08:18 AM   #3
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Thanks.

I've just re-flowed the whole board. No Luck. So I guess I'm down to components now. ah well. I might drop quad a line and check the prices of repair. (I'm re fitting my kitchen and if its cheap enough might be worth just sending it off) I've checked all pots so caps and resistors next I guess. then Transistors.

Graeme
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Old 20th July 2013, 05:56 PM   #4
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You might now want to check the driver itself. Push on the cone gently so it moves. If you feel any grating, it's been damaged.
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Old 20th July 2013, 07:39 PM   #5
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Hi

Thanks. Driver is fine. tested all OK. Ran it up with another amp and is still functioning fine I got to it in time to turn it off.
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Old 20th July 2013, 08:25 PM   #6
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Some pictures of the board may help us suggest further things. Also how was it connected up, via line inputs or speaker level?

How experienced would you say you are, eg would you be OK measuring things with a multimeter?
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Old 20th July 2013, 09:23 PM   #7
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Hi

I'll get some pics up tomorrow. no problem with multimeter or scope I have 2 scopes. I could given enough time figure out the amp stage but its really not my forty. Given some pointer where to look would be a massive help. It was hooked up at line level but no signal going through. I will disconnect the line feed to the main amp board and double check it is the power stage faulting (preamp is on another board) Unfortunately the capacitance section on my meter has failed so that's not going to help much

I'll take a few pics and get them up.

Pointers are very much appreciated.

Many thanks
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Old 21st July 2013, 09:03 AM   #8
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OK I've been out this morning and did a little more testing,

Disconnected the feed from the preamp board, no change.

Measured the high voltage rails- +64.5 (stable) -62.2~64.6 (fluctuates)

I'm guessing then I'm probably looking at duff diode in the bride? or Cap on the negative side?

Here's a few big pics. (hosted of site for size)

Graeme.me
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Old 21st July 2013, 11:50 AM   #9
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Yeah that's worth investigating. It looks like those big main caps are branded "CapXon"... aka CrapXon!

The diodes look like 1N5408 type diodes, a bit weedy for charging 10,000uF capacitors in my opinion!
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Old 21st July 2013, 12:22 PM   #10
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Hi Yes to both. I'm sure I have something in my parts bins I can replace at least for testing I'll check it out this afternoon and report back. I'm sure I have caps with enough voltage rating probably not capacitance but I'll swap the pair for testing and pull the diodes and test out of circuit. Thanks for the Interest and help.


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