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-   -   lm1875 fizzing away probelm (http://www.diyaudio.com/forums/chip-amps/227052-lm1875-fizzing-away-probelm.html)

PetruV 4th January 2013 08:03 PM

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.

PetruV 4th January 2013 08:34 PM

http://imageshack.us/a/img832/8139/dscf2872d.jpg
The black puddle above the 100k resistor at the input is a ground

PetruV 4th January 2013 08:37 PM

http://imageshack.us/a/img845/6995/dscf2871s.jpg

bobodioulasso 4th January 2013 08:52 PM

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.

PetruV 4th January 2013 09:27 PM

Quote:

Originally Posted by bobodioulasso (Post 3311337)
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

bobodioulasso 4th January 2013 10:45 PM

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).

stratus46 5th January 2013 02:45 AM

Quote:

Originally Posted by PetruV (Post 3311372)
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

PetruV 5th January 2013 08:06 AM

Quote:

Originally Posted by stratus46 (Post 3311683)
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

PetruV 5th January 2013 08:42 AM

Now works did the scematic as in the image and adding the componets in red

PetruV 5th January 2013 08:43 AM

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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