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741 circuit amp wont turn on

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Jeorge

Oct 31, 2016
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I have built a small amp circuit with a light in the circuit. But the light wont turn on and no power is going through the board. I have used different types of rechargeable and normal non rechargeable 9v batteries, but still no power. My amp circuit is made up of a resistor, capacitor and 741 op amp.

Any help and advice would be appreciated.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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Post a schematic. Draw it on paper if you have to and take a picture.
 

Jeorge

Oct 31, 2016
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Heres my drawn schematic.....Hope it makes sense.

upload_2016-11-1_7-24-24.png
 
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davenn

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Heres my drawn schematic.....Hope it makes sense.

as drawn, no it wont work

you have a capacitor in line with the input, why? is there a DC or AC voltage going in there ?
you have a capacitor in line with the lamp, again, why ? do you know DC doesn't go through a capacitor ?

you have the lamp going back to the non inverting input ( the + input), this is incorrect the + input, the lamp should be going to 0V
when pin 4 of the op-amp is going to
ohhh and you have pin 4 marked as 9V instead of 0V



Dave
 

Herschel Peeler

Feb 21, 2016
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I have built a small amp circuit with a light in the circuit. But the light wont turn on and no power is going through the board. I have used different types of rechargeable and normal non rechargeable 9v batteries, but still no power. My amp circuit is made up of a resistor, capacitor and 741 op amp.

Any help and advice would be appreciated.

What does it take to light the lamp? Voltage? Current?
The LM741 can't put out much current. And the more current you draw the lower the output voltage.
What voltage in?
Try it without the capacitors.
 

BobK

Jan 5, 2010
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No, this will never work, even without the capacitors. The input pins cannot source or sink current, and that is what your circuit is expecting.

How about telling us what you are trying to do. I cannot determine that from the totally flawed schematic that you posted.

Bob
 

Audioguru

Sep 24, 2016
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I suspect that he wants the light bulb to light up when there is a low level AC signal at the input. Then a properly biased amplifying opamp van drive a rectifier/filter circuit that drives the light bulb.

The datasheet for a 48 years old 741 opamp says that its non-inverting input pin3 will not work if it is within a few volts from ground but here it is at ground.

The incandescent light bulb has no voltage or current rating. If its part number was shown then we could look them up.
 

davenn

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Thread is closed
till the OP responds to me

@Jeorge

please PM me if you understood what was commented on and you have further info to add
and I can reopen the thread


Dave
 
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