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View Poll Results: Was a good idea to use two lm1875 or a big stk chip
Use stk 8 27.59%
use lm1875 21 72.41%
Voters: 29. You may not vote on this poll

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Old 4th January 2013, 08:03 PM   #1
PetruV is offline PetruV  Romania
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Default lm1875 fizzing away probelm

This is my thread in which i will post all of my work and ask for all of my help.Sadly you cant change the name of the thread,go to last page to see my latest problems
Please excuse my excessive amount of demanded attention,that has been pointed out to me.

Last edited by PetruV; 10th February 2013 at 08:10 PM.
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Old 4th January 2013, 08:34 PM   #2
PetruV is offline PetruV  Romania
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Click the image to open in full size.
The black puddle above the 100k resistor at the input is a ground
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Old 4th January 2013, 08:37 PM   #3
PetruV is offline PetruV  Romania
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Click the image to open in full size.
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Old 4th January 2013, 08:52 PM   #4
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Pin 1 must be at Vcc/2.
Why the two 100k resistors marked red on your schematic? They provide Vcc/2 at input pin.
You need them and the ground can't be as you made it.

Last edited by bobodioulasso; 4th January 2013 at 08:56 PM.
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Old 4th January 2013, 09:27 PM   #5
PetruV is offline PetruV  Romania
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Quote:
Originally Posted by bobodioulasso View Post
Pin 1 must be at Vcc/2.
Why the two 100k resistors marked red on your schematic? They provide Vcc/2 at input pin.
You need them and the ground can't be as you made it.
I was tired and i thought they werent needed and i wanted to see how it sounded,it took me 2 hours to solder all that crap in cause my soldering iron sucks and i never used perfboard
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Old 4th January 2013, 10:45 PM   #6
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You must follow the schematic for single supply.
Have a look at datasheet.
When +/- supply is used those resistors are not needed because the input pin , referenced to ground is at Vcc/2.
When a single supply is used a Vcc/ 2 point is created with two equal resistors (and a cap).
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Old 5th January 2013, 02:45 AM   #7
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Quote:
Originally Posted by PetruV View Post
I was tired and i thought they werent needed and i wanted to see how it sounded,it took me 2 hours to solder all that crap in cause my soldering iron sucks and i never used perfboard
Helpful hint: When a manufacturer says parts are optional they can be safely omitted but don't make changes unless you fully understand.

G
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Old 5th January 2013, 08:06 AM   #8
PetruV is offline PetruV  Romania
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Quote:
Originally Posted by stratus46 View Post
Helpful hint: When a manufacturer says parts are optional they can be safely omitted but don't make changes unless you fully understand.

G
I udestood it but i did the modification that was marked in red and it now works
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Old 5th January 2013, 08:42 AM   #9
PetruV is offline PetruV  Romania
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Now works did the scematic as in the image and adding the componets in red
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Old 5th January 2013, 08:43 AM   #10
PetruV is offline PetruV  Romania
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It broke,it makes a lot of sounds even when its not hoked up to my pc,i think it starts to oscilate making a very loud noise
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