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Need help on Logitech Z-2300

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othello999

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Hi, can anyone help me to identify the values of L400 and L402 inductors on the Logitech Z-2300 motherboard? they are located near TDA amplifiers. Thanks in advance.
 
Doesn't the datasheet for the TDA amplifier ICs recommend the value of inductors?
 
ST Micro does not recommend inductors for the TDA9296 amplifier IC. Maybe Logitech uses the inductors in a different part of the circuit.
 
ST Micro does not recommend inductors for the TDA9296 amplifier IC. Maybe Logitech uses the inductors in a different part of the circuit.
No, it connects to the third (3) pin (NON INVERTING INPUT)of the TDA7296 amplifier. So I presume that it works like a LC filter.
 
None of us can find information on your mother board.
A good close up picture might help.
BIG QUESTION: why? why do you need information?
Well because I needed to replace a bad TDA7296 amplifier, but on the PCB there were lots of glue. While I tried to remove metal plate which pins all 4 of the TDA amplifiers to the radiator (which was also glued to the PCB) , I accidentally removed it with the glue and in it were two inductors.... so now I need to find their nominals so I could replace them... :)
 

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That looks more like a ferrite bead on a piece of wire rather than an actual inductor.

If the datasheet doesn't show an inductor, then it probably doesn't need one.

I would suggest drawing the circuit of the output stage out fully, and comparing it to the datasheet.
 
I can't see any components on your picture that look like inductors. It would have helped if you had said that this was an amplifier rather than describing it as a motherboard. I assume others (As I did.) assumed you were talking about a computer mother board.

Edit. After seeing Nigel's reply It looks like the option of fitting these components was not used. What is the fault an you equipment ?

Les.
 
Last edited:
I can't see any components on your picture that look like inductors. It would have helped if you had said that this was an amplifier rather than describing it as a motherboard. I assume others (As I did.) assumed you were talking about a computer mother board.

Edit. After seeing Nigel's reply It looks like the option of fitting these components was not used. What is the fault an you equipment ?

Les.
Sorry if I have mistaken you, but you get my point now and that's what matters.
I had one faulty output channel (left speaker didn't work) and I have found one defective TDA7296 amplifier. In order to replace it I had to remove metal plate that I mentioned earlier. And that's how I have damaged these inductors :)
 
That looks more like a ferrite bead on a piece of wire rather than an actual inductor.

If the datasheet doesn't show an inductor, then it probably doesn't need one.

I would suggest drawing the circuit of the output stage out fully, and comparing it to the datasheet.
Exactly, this is a small toroidol inductor with ferrite core.
I think that these form a RLC low-pass filter. So the audio signal comes from dual operational amplifier (4565 IC) then passes the RLC low-pass filter and afterwards travels to TDA7296 amplifiers input. So if I would replace these small inductors with a peace of short wire, wouldn't the signal be distorted?
 
I can't see any components on your picture that look like inductors. It would have helped if you had said that this was an amplifier rather than describing it as a motherboard. I assume others (As I did.) assumed you were talking about a computer mother board.

Edit. After seeing Nigel's reply It looks like the option of fitting these components was not used. What is the fault an you equipment ?

Les.
Also you can't see these inductors, because they are ripped off :) (my mistake for trying to remove glue without inspecting what's underneath it first)
 
Exactly, this is a small toroidol inductor with ferrite core.
I think that these form a RLC low-pass filter. So the audio signal comes from dual operational amplifier (4565 IC) then passes the RLC low-pass filter and afterwards travels to TDA7296 amplifiers input. So if I would replace these small inductors with a peace of short wire, wouldn't the signal be distorted?

No, there's no need for the inductors, as shown on the datasheet.

I would imagine they are there to help reject any strong RF signals (for if you live next door to a big transmitter), and FAR too low a value to affect audio in any way.
 
The Logitech Z-2300 speaker system has a subwoofer and two low power satellite speakers. The TDA7296 amplifier ICs drive the satellites with mid-range and high audio frequencies. Maybe the inductors are part of the crossover frequency dividing system (high-pass filters, not low-pass filters). Without a schematic we are just guessing. If the inductors are part of the crossover then removing them will cause low frequencies to destroy the tweeters.
 
The Logitech Z-2300 speaker system has a subwoofer and two low power satellite speakers. The TDA7296 amplifier ICs drive the satellites with mid-range and high audio frequencies. Maybe the inductors are part of the crossover frequency dividing system (high-pass filters, not low-pass filters). Without a schematic we are just guessing. If the inductors are part of the crossover then removing them will cause low frequencies to destroy the tweeters.

It would be EXTREMELY unlikely that the crossover is done passively in the input of the power amp :D

It will almost certainly be done actively much earlier on.

But a drawing of the circuit around the output stage would help.
 
I have made audio equipment for radio stations. The RF fields are strong and cause strange things to happen in some audio amplifiers. I use ferrite beads to remove the RF. If this is the case then just short out the coil. (solder a piece of wire across the coil)
 
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