General Electronics Repair - Subwoofer Relay

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I hope there are some electronics experts that could help me on this and I apologize for it being not directly arcade related. I have a Klipsch SW-450 subwoofer that has stopped working. Cosmetically it is in pristine condition. The problem seems to come from the plate amp. When I plug it into a power outlet it makes a faint rapid clicking sound. The funny part is this noise occurs no matter what state I have the sub in (On, Off, Auto). So even when set to off it happens as soon as the unit is plugged in. I immediately assumed it was a power relay. I tried the official Klipsch support but since it is a couple of years old they are asking a price that is just shy of buying a new sub. I pulled the plate amp off and looked at the circuit board. I see no darkened areas and no capacitors that appear to be swollen or broken.

I am attaching a photo of the circuit board. My hope is that someone in the western Chicago suburbs that has the electronic skills to diagnose and determine if it is worth fixing or not. I'd hate to throw it away because other than this the thing is perfect. If it is possible to fix the relay or power transformer or whatever the problem may be for 50 bucks or less I would greatly appreciate it.

I have a video that shows the sound but I don't know how to upload that.
 

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I've fixed powered speakers before. Unfortunately, Klipsch has decided to have potting wars, which will make fixing this difficult.

For starters, try this: run your finger over the top of that TL494L and see if you feel any catches. If you do feel a catch (crack), buy a new one and either solder it in, or socket it and install it. I found a bad Op Amp on a powered speaker this way, and just socketed it and replaced it.

The vendors are no help - they design these to be break and dump and buy new. They wouldn't even release a drawing - I had to sketch out the circuit myself on the last one. No help at all - almost hostile when I called and asked for a drawing.

The potting may have been an effort to keep traces from breaking (since sub woofers have large impulse loads [thump thump thump] and literally shake things to failure). However, it looks like the same potting crap I ran into on that powered speaker rig, and if it is it's hard as rock and hard to remove. I broke a diode removing some of it, and had to get a new diode.

If you don't feel cracks, then I'd suggest re-flowing all the major components on the underside of the board and try to get it working again. All it takes is a cracked solder joint, and you'll have problems. Start with a jewelers loupe or a good magnifying glass, and look for bad connections.

Given the price, you have little to lose but time.
 
On a closer look (blowing up your picture), I see three devices. They could be rectifiers, or power amps (the large aluminum heat sinks are a tip off that they are one or the other).

If these are bad, the amp won't work. Do you have an ohm meter? Can you read the numbers off those devices (circled in yellow highlighter)?

Those could have failed. The vendor of course, screwed them to the heat sink so we'd have to see if we could de-solder them, remove the heat sink and them, pull the screw, add thermal compound, re-assemble and re-solder in.

No guarantees as it could be something blown under the potting that we can't see or easily reach. Assuming the heat sinks are removable, this will be at least 2 hours of work with R&R and sourcing parts, and that's more than your $50 limit.
 

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And of course, the vendor has stuck a fuse in the circuit. Ohm this out and see if it is open. Look for other fuses as well.
 

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And if that fuse is cleared, Amazon has some for a princely sum.

No shipping if you are an Amazon Prime member.
 

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Unfortunately there isn't a power relay on that board. That looks very much like a switching power supply board. It output +/-9V and then whatever that two pin (red/black) connection is (45V would be my guess). The click you are hearing is probably the magnetostriction of the transformer or one of a few other parts as the power supply tries to start up, and them immediately shuts down. Crazy amount of potting not withstanding, troubleshooting a switch mode power supply takes a bit of work.

You've best bet is probably just to replace the whole plate with a new amp. Something like this would be a starting place.

https://www.parts-express.com/bash-300s-digital-subwoofer-plate-amplifier-300w-rms--300-750
 
Take the unit into complete darkness later tonight, and plug it in.

If your clicking noise is due to arcing, you might be able to see it.
 
Thanks to everyone for the help. Based on the advice, it sounds like it could be a lot of effort and the poor decisions by Klipsch makes it difficult to identify. It seems like buying a new plate amp would be the solution however for that price I may not want to stick with the rest of the Klipsch and pit the money towards something better.
 
It's your call. If you have an ohmmeter, I'd suggest checking the fuse and those three devices I circled in yellow, and running your finger back and forth on the top of the exposed IC.

If you don't have an ohmmeter, well, you could buy one. They aren't hard to use.
 
Thanks to everyone for the help. Based on the advice, it sounds like it could be a lot of effort and the poor decisions by Klipsch makes it difficult to identify. It seems like buying a new plate amp would be the solution however for that price I may not want to stick with the rest of the Klipsch and pit the money towards something better.

Unless you can get someone to do the work for free, it is highly unlikely that you can repair your existing amp for under $100 and if you put a new plate amp in, you're in the $150+ range. Given that an SW-450 is $125-$175 on Craigslist, repair certainly isn't going to be the most cost effective solution. Unless you want to do it on the principle of not throwing away equipment that can be repaired, putting money towards a replacement is probably the best option.
 
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