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Old 23rd January 2010, 03:52 PM   #1
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Question help regarding tda7265 mute pin

hi guys or rather geniuses!!
i think i'm in kinda unique problem . i am getting around +6v on my mute pin . which according to datasheet of tda7265{st microelectronics} should be less than -6v to be in play mode.

my voltage around the circuit is 11v . also i'm getting 2v output with no input.
plz help me
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Old 25th January 2010, 01:04 AM   #2
gootee is offline gootee  United States
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Disconnect the power. Check the circuit. If you can't find any errors by visually inspecting it, then, if you have a multimeter, measure the resistance between all pairs of points that the schematic says should be directly connected to each other, and make sure that it is very low, in each case. If that all checks OK, measure between all pairs of points that the schematic says should NOT be connected to each other, and make sure that the resistance is very high, in each case. (Note that the resistances actually measured might vary, depending on installed components. If necessary, uninstall components.)

Posting a schematic, and some photos of your actual build, might be very helpful.

What do you have connected to the mute pin, for example, to pull it below -6v for play mode? And I hate to ask, but, did you measure with the proper test-lead polarity?

Also, when you measured the 2v output with no input, you should have been measuring the output when the input was shorted to ground. Was that what you did?

Did you have a load connected?

Tom

Last edited by gootee; 25th January 2010 at 01:11 AM.
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Old 27th January 2010, 06:40 AM   #3
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well thanks for your quick response. but i guess its too late to check circuit throughly, as i was very much excited to make my first amp. and that excitement blown my ic into two part.

and now i have decided to use lm1875 as it is easy to use and have no mute pins to screw me.
what do you say ??

also if you can share your lm1875 project with me , it will be a great help.
i am also using lm3875 for my subwoofer.

plz suggest.
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Old 28th January 2010, 09:32 PM   #4
johnr66 is online now johnr66  United States
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I say good choice. The TDA 7264/7265 has one of those retarded mute circuits that will kill the chip if it is biased with the wrong voltage by accident. It also requires odd voltage ranges to set the chip into a certain mode.

The mute pin requires +Vs-6v to be in play mode. I used a 7 volt zener so I could use the chip with different supply voltages yet keep it in play mode. It has been a while since I tinkered with this chip, but simple grounding the mute pin (or was it a negative voltage with respect to ground?) will put the chip into "death mode" where it internally conducts heavy currents and kills itself.

I always setup chips amps on a variable dual voltage supply with 1 amp current limit. This has saved many chips from me botching a lead or something in the wrong place.

Anyhow, The LM1875 is a good chip to learn on. Have fun!

Last edited by johnr66; 28th January 2010 at 09:35 PM.
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Old 28th January 2010, 10:00 PM   #5
mjf is offline mjf  Austria
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hello.
there are many lm1875 projects in the chip amp forum.
have a look...........
greetings
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Old 30th January 2010, 03:21 PM   #6
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hey thanks john. i know tda's are worst to deal with . but thanks to national semiconductor who had made good chips like lm1875.

you will be glad to know that i have successfully built the amp. it's good. but i am facing problem regarding 18-0-18v power supply .

i did'nt get one so i tried with 12-0-12, it's good but sound is not so loud .

is this because of my power supply???

i am using esp project 72 circuit diagram..

help
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Old 30th January 2010, 03:25 PM   #7
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thanks mjf i have looked around and found many helpful sugestions and guides.
thanks for your concern.
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