Genius desktop speakers

[sam67]

Hi Guys ,

Plugged my speakers in to listen to some sounds on pc and noticed that one speaker is not working..There are only 2 speakers which have a power adapter .

I have took them apart and i know the speaker that stopped working works as i unsolder-ed it and swapped it with the working one and it was fine..

Got the pcb out and cannot find anything burned and the caps look good they say 100uf 16v SU' SCON never heard of em lol..The main cap is a 1000uf SU' SCON.Could a faulty cap cause a speaker to not work ? Theres not much on the pcb board component wise.

Power is ok ,so i am thinking either lead to that speaker is not much good or a fault some where on the board.But the speakers have not been moved so i don't think it is the lead.

Any tips while i have this apart..I know i can go and get another pair of speakers but just wanting to find this problem out.

Cheers guys.

[Krankshaft]

Re: Genius desktop speakers

If there are no broken joints inside start bending the speaker out wire.

Especially at the strain relief where the 3.5mm connector is. Run a continuity check from all 3 wires Left speaker +, Right Speaker +, and ground. Also check the wire linking the two speakers together.

If that all checks out then you're looking at a dead amplifier channel.

[sam67]

Re: Genius desktop speakers

Thanks Krankshaft,

Will try what you said,i did notice on the pcb that there were 2 ic chips with a heat sink on top of each one ..could one of these have blown ? are these for each speaker because the speaker that's not working is just basically a shell to house the little speaker and the main speaker that works houses the pcb for both if you get me lol.

P.s i might have to pierce the cable as it is sealed near the 3.5mm connector just 2 wires on same lead that go to the none working speaker..

[Krankshaft]

Re: Genius desktop speakers

No need to pierce anything just measure from the end connector to where the wire solders to the PCB. If there is a break in one of the wires you won't get continuity. It's very important to check the input cable from the computer for continuity first though the amps can't amplify anything unless they're getting both channels.

Second would be to check the wire from that empty speaker case back to the main unit.

Yes it's very common for the complete amplifier unit to be housed in one speaker. Some even have a small transformer and rectifiers inside if they don't use an external wall wart.

Two heatsinks means that each channel has it's own amplifier. If both the cables check out you're looking at a bad amplifier IC trace back from the input wire of the bad speaker to the output of it's respective amp. That amp is the one to replace.

[momaka]

Re: Genius desktop speakers

It's very important to check the input cable from the computer for continuity first though the amps can't amplify anything unless they're getting both channels.

I agree. Start from there, then check the connection between the speakers (sometimes those small jacks like to break - I've had that problem with my computer's speakers too). You can also try plugging your speakers to a MP3 player or a portable CD player to check that. If you don't get anything, it's either the amp or the connection between the speakers like Krankshaft said.

[sam67]

Re: Genius desktop speakers

Hi Guys ,

I have tried a continuity test on the wires and they seem to be fine ..So i uploaded a few pics..

I think its one of the ic chips that might have blown .. Trouble is not sure which one tried to follow the wires but they don't give me a clue to which chip..The photo in pic 9 has the ic2 chip next to the on off vol and control knobs.

If i manage to take out the right chip with some help from you guys ( if you can tell from the pic lol) would the 1 speaker still work with just the one chip in place ( i'm guessing yes but i may be wrong) .

I know i could buy another cheap pair of speakers but i like the idea of trying to see if i can get it to work ..The red and black wires that are on the pcb are for the speaker and i have tried them on both speakers and the speakers are fine. This is the main housing that supplies both speakers.

Hope you understand me

Thanks in advance.

[hardwareguy]

Re: Genius desktop speakers

If the wires check out, its either a bad amp IC (they are cheap) or perhaps a bad coupling capacitor. THe coupling caps are small, 2.2uF or less wired in series between the input and the amp.

If the amp is single ended, ie, the speaker - connects to ground and the speraker + connects to the amp chip there will be an output coupling cap in series between the speaker and amp, usually on the +. This cap is larger, 100uF or bigger. If this goes bad the amp will not work either.

Bridge tied load (BTL) amps and amps with dual rail power supplies do not use output coupling caps.

[sam67]

Re: Genius desktop speakers

Thanks hardwareguy,

I have 15 small 100uf 16v caps and 1 big 1000uf 16v cap then a few ceramic disc caps ... i reckon it might be ic ..Trying to de-solder the heat sink on top of ic seems to me soldered sold to pcb ..Is there a way test ic with dvm ..Once i get the ic off i am just gonna get a new one and try it..No burn marks on board and resistors are all in spec and diode also.

Cheers

[Krankshaft]

Re: Genius desktop speakers

The only real way to check it is with an oscilloscope probe the input pins with the amp on and while inputting an audio signal (it can be an Ipod or even better a tone generator they have apps for this on the pc) and you will see a small amplitude signal.

Probe the output and if the amp is working you will see it amplified the amplitude of the waveform will be larger than the input hence the term amplifier. If the amp is faulty you won't see anything.

[sam67]

Re: Genius desktop speakers

Just an update as i have only just managed to desolder the ic tonight due to other things..Now the ic is a TEA2025B AUDIO IC ..Now i have found one Which matches this but there is a second number underneath..

Mine says on the ic ST TEA2025B,W990335 Malaysia..The one i found says the exact spec as mine apart from the W990WO346 is this number just part of the manufacturer and does it matter or not about this last number.

Looks like i'll have to get a couple from abroad as i cannot find one here on the web for uk. unless i have missed it lol.

Thanks ..also this had a heat sink soldered on the ground pins numbers 4 and 5 on both sides..Is it ok to use some thermal grease that i have as this looks like it had some on.

Thanks in advance.

[pfrcom]

Re: Genius desktop speakers

W990335 maybe just a date code, manufactured 335th day of 1999

Other W number is a bit more complex - is it quoted accurately ?

[sam67]

Re: Genius desktop speakers

Hi i am guessing it's right here's is the link if it's ok to post it http://www.kpcomponents.ca/product_i...oducts_id=3115

When you click the larger icon on the page it shows a close up of the part..

Thanks

[hardwareguy]

Re: Genius desktop speakers

TEA2025 is a VERY common amp IC made by ST Microelectronics. Getting one should be easy.

[sam67]

Re: Genius desktop speakers

I have ordered 4 from the US it only cost $5 ..here in uk i could get them for £1.45 but they wanted £12 for shipping and that's from a uk company ..So i am now waiting for them to come from US ..Can't believe they wanted all that for shipping here in uk from a uk company.

[Radio Fox]

Re: Genius desktop speakers

The only real way to check it is with an oscilloscope probe the input pins with the amp on and while inputting an audio signal (it can be an Ipod or even better a tone generator they have apps for this on the pc) and you will see a small amplitude signal.

Probe the output and if the amp is working you will see it amplified the amplitude of the waveform will be larger than the input hence the term amplifier. If the amp is faulty you won't see anything.

Before I could afford my first oscilloscope, I used to use a Micronta Transistorized Signal Tracer. It was simply a sensitive audio amplifier built into a small plastic box with a volume control & small loudspeaker on the front.

It came in real handy for fault finding radios & amplifiers. I have still got it actually. I must have bought it in the late 70's from Tandy (Radio Shack in the US).

Don't know if you can still buy them, or it might be worth building one if you cannot afford a scope.

[sam67]

Re: Genius desktop speakers

Just like to update about the speakers..

Well i got the ic audio amplifiers from the U.S and solder it in tonight ( been busy recapping monitors lol) Well i put the thermal paste on top of ic amp and heat sink and soldered it to the pcb..Well i plugged her in and all works fine ..so jobs a good one

Must say these speakers were not that much to buy but i wanted to see if i could fix them ,rather than throw them away and now they are back to life again (plus i have spare ics if they ever go again ,for just under $5 inc shipping)

Also did a few tests on the good ics with ohm meter and tested the bad ic ,all the good ics had same reading and bad one had 2 places where the ohms were really low..So i guess you can tell if you have a new ic to compare.

[momaka]

Re: Genius desktop speakers

Congrats on getting them fixed!
Now go crank up that music .