I inherited this speaker set, which has been working fine until recently: CyberAcoustics CA-3712BT.
I was playing fairly loud music for a while (1-2 hours, listening from another room), and suddenly the subwoofer cut out.
The other smaller speakers still produce sound fine.
My guess is that something overheated, and maybe even burnt out, but I'm not sure.
I opened the case, and the power transformer was very hot, as well as the heat sink that's near it (not attached, but nearby when it's assembled).
Some pictures are below.
I also noticed an electronic component attached to the heat sink, which I thought maybe was a temperature sensor - so maybe it cut itself off to avoid overheat? But even after letting it sit and cool a while, it's still not working.
I'm trying to get an idea of whether it's worth repairing or not.
Pictures: imgur listing
Questions:
Thanks for any input!
I was playing fairly loud music for a while (1-2 hours, listening from another room), and suddenly the subwoofer cut out.
The other smaller speakers still produce sound fine.
My guess is that something overheated, and maybe even burnt out, but I'm not sure.
I opened the case, and the power transformer was very hot, as well as the heat sink that's near it (not attached, but nearby when it's assembled).
Some pictures are below.
I also noticed an electronic component attached to the heat sink, which I thought maybe was a temperature sensor - so maybe it cut itself off to avoid overheat? But even after letting it sit and cool a while, it's still not working.
I'm trying to get an idea of whether it's worth repairing or not.
Pictures: imgur listing
Questions:
- How can I verify if, in fact, this transform is burnt out? I have a multimeter, but not sure exactly what to measure.
- Is this something I could replace, if it is burnt out? I didn't see any obvious off-the-shelf parts that match it, and I'm uneasy trying to mix-n-match parts that are rated for different volts,amps. It has 2 sets of wires (2X11V - 1A - Blue/Black/Blue, 8V - 0.3A Yellow/Yellow - see pictures)
- Any other guesses what might be wrong?
Thanks for any input!
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The five-legged thing on the heat sink is a power amp IC.
This central unit powers the small speakers? And they are still working? Then the transformer is working.
First thing I would do is check teh woofer speaker to see if the speaker itself still works.
This central unit powers the small speakers? And they are still working? Then the transformer is working.
First thing I would do is check teh woofer speaker to see if the speaker itself still works.
First stop is to test the speaker.
Check it for ohms with your DMM.
Somewhere between 3 and 8 ohms should be OK.
If its the speaker then obviously need to find a replacement.
If not then could be just a bad connection ?
If your speakers are blowing you need to turn it down a bit or the same problem might occur or buy a higher power rated replacement.
Check it for ohms with your DMM.
Somewhere between 3 and 8 ohms should be OK.
If its the speaker then obviously need to find a replacement.
If not then could be just a bad connection ?
If your speakers are blowing you need to turn it down a bit or the same problem might occur or buy a higher power rated replacement.
Push the woofer cone in with your hand. It should move in and come out smoothly with no sound. If it scrapes then the coil is burned out. If the coil burned out it is quite possible that the amplifier chip for the woofer is blown as well, because the damaged coil scraping on the magnet pole can cause quite a lot of arcing in the process of dying.
It is a Bluetooth speaker with auxiliary speakers. $ 49 retail.
No idea how much repair will cost...
Buy an old car speaker and fit it, if the old one is blown, quite likely, looks cheap. Or from old TV, radio...
No idea how much repair will cost...
Buy an old car speaker and fit it, if the old one is blown, quite likely, looks cheap. Or from old TV, radio...
I measured the speaker resistance, and got 3.7 ohms. Seems reasonable, from what you say?
Another idea was the power transformer's thermal fuse might be triggered, but I measured across the outlet plugs and got 37.3 ohms, not an open circuit... Plus, the small speakers work, so obviously power is working to some extent.
I don't think there are loose wires or anything though - all the soldering and clip-on connectors seem solid. Is that what you meant by "bad connection" ?
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It moves smoothly and silently.
Also measured resistance across the speaker wires (unplugged from board) and got 3.8 ohms, which other people indicated is normal.
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If the heatsink gets hot when it is just powered up then its a fair bet the chip bolted to it has failed. With no music playing it should run almost cold.
What type is it? Something like a TDA2030 or TDA2050.
What type is it? Something like a TDA2030 or TDA2050.
That's a new idea, thanks. I powered it on for a few minutes and it is noticeably warm if I put my finger on the sink near the chip. Waiting a few minutes it does seem warmer still (not truly "hot" yet though; been ~10min).
I don't see any TDAxxx marker on it; it's just an unmarked black chip w/5 pins.
Another thing I have noticed is that when I switch inputs it makes its little "boopdeeboop" sound, and I can hear a very feint output from the subwoofer when that happens. So it's not like it's fully broken, somehow...
Is the idea that maybe this chip needs replacement?
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Yes, all the power comes through that transformer. Though it is multi-output (2x 11v 1A, 1x 8v 0.3A), so I don't know if maybe one of the outputs is burnt, which powers the subwoofer, but other parts are not affected? Not sure if that's how multi-output transformers work...
But yes, the small speakers are receiving power, and at least the primary of the transformer is fine, it seems.
I unplugged the subwoofer speaker and measured it to be 3.8 ohms. And it doesn't have any issues when I push on it; seems to be okay?
Only other idea I heard was that it could be the amp chip itself, maybe?
Check the voltage between pins 3 and 5
If around 20, it is 2030, above 24, it is a 2050, and up to 48 it is 1875.
You can safely put a 1875, mount it properly on the heat sink.
Most of these are copies, legally or not, but the originals except 1875 are no longer in production.
Copy quality varies from good to terrible...
Another reason could be leaky capacitors and resistors, check those out.
Oh, and see the DC volts going to speaker, if above 50 mV or so, change the chip.
If around 20, it is 2030, above 24, it is a 2050, and up to 48 it is 1875.
You can safely put a 1875, mount it properly on the heat sink.
Most of these are copies, legally or not, but the originals except 1875 are no longer in production.
Copy quality varies from good to terrible...
Another reason could be leaky capacitors and resistors, check those out.
Oh, and see the DC volts going to speaker, if above 50 mV or so, change the chip.
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I think it has to be favourite tbh. It should not get remotely hot at all when just powered up. Barely detectable heat after a couple of minutes is all there should be.
If there is no number on it then you would need to try and identify it from the circuit configuration and component values and refer to a data sheet for the chip to see the pinouts.
As well as the TDA devices the other possibility is an LM1875.
The supply voltages used would be a big clue, however to measure those accurately would possibly need the IC removing first as it could be pulling them down due to the smallish transformer used.
If there is no number on it then you would need to try and identify it from the circuit configuration and component values and refer to a data sheet for the chip to see the pinouts.
As well as the TDA devices the other possibility is an LM1875.
The supply voltages used would be a big clue, however to measure those accurately would possibly need the IC removing first as it could be pulling them down due to the smallish transformer used.
Small follow-up on this: I was fiddling around with it while plugged in, and pushing on the speaker, and noticed that it can get into a state where instead of producing a tiny amount of sound, it produces 0 sound except a straight hum.
And in this state, with nothing else going on, the heatsink gets HOT. So, I assume there is some flaky connection, but somehow it gets fully shorted out after fiddling with it? Does it still seem like that chip could be the culprit?
And in this state, with nothing else going on, the heatsink gets HOT. So, I assume there is some flaky connection, but somehow it gets fully shorted out after fiddling with it? Does it still seem like that chip could be the culprit?
You are right, 1 is signal in...
3 and 5 it is.
Does the speaker make any sound when meter is connected, a scratchy sound?
If yes, it is okay.
But if it sort of gets stuck, then the coil may be sticking.
Check the speaker on another source, or connect to the amp used for the smaller speakers, after removing the connections from the doubtful chip.
That will tell you a lot. Also, check with another speaker connected to the wires used for the big speaker.
That will tell you circuit or speaker is faulty.
3 and 5 it is.
Does the speaker make any sound when meter is connected, a scratchy sound?
If yes, it is okay.
But if it sort of gets stuck, then the coil may be sticking.
Check the speaker on another source, or connect to the amp used for the smaller speakers, after removing the connections from the doubtful chip.
That will tell you a lot. Also, check with another speaker connected to the wires used for the big speaker.
That will tell you circuit or speaker is faulty.
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I *think* I did this correctly, but got some crazy numbers.
I did:
- Unplugged speaker from board
- Put voltmeter on those two pins on the board
- Turned on system
The hum is also a big sign the chip has failed.
It is putting DC voltage across the speaker which will do it no good at all. That is why the chip is hot and the transformer got hot.
It is putting DC voltage across the speaker which will do it no good at all. That is why the chip is hot and the transformer got hot.
Just identify the chip and get it swapped 😉
Remove it first (use solder braid to do that) and then measure the supply voltage between pins 3 and 5 of the chip and we can then make a partial guess as to what might be fitted.
If we are not sure you might have to look at component values around the chip to help try and figure what was in there but is almost certain to be one of those three types.
Remove it first (use solder braid to do that) and then measure the supply voltage between pins 3 and 5 of the chip and we can then make a partial guess as to what might be fitted.
If we are not sure you might have to look at component values around the chip to help try and figure what was in there but is almost certain to be one of those three types.
And if is not a staggered 5 pin chip, a photo please.
Also a photo of the heat sink and power capacitors.
Could be the chip went due to continuous overload, thermal shutdown or whatever happened.
Along with the chip, heat sink may need to be made bigger...and a few holes in the box may be needed.
Also a photo of the heat sink and power capacitors.
Could be the chip went due to continuous overload, thermal shutdown or whatever happened.
Along with the chip, heat sink may need to be made bigger...and a few holes in the box may be needed.