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PostPosted: 15 Mar 2021, 21:38 
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Attachment:
03_12_2021 Schematic LM4862 amp circuit.pdf

I'm a novice at electronics. The amplifier circuit below has been tried and failed by now using at least five new chips. I am trying to build a basic amplifier circuit around the Texas Instruments LM 4862 amplifier chip. It consistently fails to produce any output. Is it possible that each time I am burning out the LM 4862 chip while soldering? The soldering iron temperature is set at 510° Fahrenheit. The circuit schematic is found in my attachment "03_12_2021 Schematic LM4862..." Any reply would be appreciated.


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PostPosted: 22 Mar 2021, 15:09 
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Joined: 19 May 2011, 05:38
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If you are getting your chips of ebay they maybe fakes. go with mouser, digikey,etc.


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PostPosted: 22 Mar 2021, 17:19 
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Attachment:
Top down view of chip with glue.pdf
Attachment:
Vol+,VDD,Gnd,Vol-.pdf
Attachment:
5 volt power components.pdf
Attachment:
Audio-in,In-,In+,Bias,SDN.pdf
Chips come from Mouser. 3/20/2021 I took great care not to fry the amplifier chip but I still get no sound - not even a crackle when plugging in or withdrawing from the jack. Can anyone bring their lights to bear on my implementation of what's in the schematic. Being a newbie I probably did something wrong. The input signal is from the earphone jack of an MP3 player that I built. 8 volt battery which the voltage regulator reduces to 5 volts. R2 is 22K while C4 is optional so I didn't connect it - it's for a gain higher than 5 where a 22pf C4 (capacitor) would be used. The two jacks are in perfect operating condition. Current is coming out of the voltage regulator. In principle I try to connect the negative lead of a capacitor first at the beginning and the positive lead to the next part of the circuit.


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PostPosted: 22 Mar 2021, 17:54 
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Joined: 06 Apr 2009, 10:08
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Location: US Pacific Northwest
It's very difficult to see the circuit from your pictures. There is also a lot of confusion regarding the actual wiring. Here are some suggestions.

1. Use an IC socket and don't solder directly to the chips.
2. Use through hole components and mount all the components on one side of the board. Then make connections on the back side of the board. This will keep things neater.
3. Use a little larger piece of board so that your components are laid out like the schematic.
4. Use a rectangular board and put the audio circuit on the left side (looking at the component side) and the power supply on the right side.
5. Do a detailed drawing of the board before you begin assembly. Check the schematic against your diagram, check the circuit build against the schematic, and check the diagram against the build.

Post your diagram before you try the build again. Ask for inputs at that time.

I hope this helps. Good luck.

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PostPosted: 22 Apr 2021, 23:03 
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Attachment:
Schematic_.pdf
This is the layout for the circuit that I want to make. I'll clean it up when I have time. Then I will space out the components so that one can easily see in my photos how the connected components are copying what's in the diagram.


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PostPosted: 23 Apr 2021, 19:12 
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There are some basic problems with your circuit as drawn.

First in the power supply section. The 10µf capacitor after the battery should be between the positive contact and ground. It is shown inline with the positive power lead. The 0.1µf capacitor connected to the Vdd (pin 6) contact, should also be between the pin and ground. This is also shown inline with the amplifier chip. Both of these errors will prevent power from getting to the amplifier chip.

The 1.0µf bypass capacitor is also shown inline between the "Bypass" pin (pin 2) and the "+IN" pin (pin 3). These two pins should be tied together and then the bypass capacitor should be connected between the two pins and ground. With the capacitor inserted as you have drawn, this will prevent the boost amplifier on the chip from operating.

The amplifier should be wired according to this diagram in the application sheet.
Attachment:
LM4862 typical Circuit.png

Please look at the differences, correct your diagram and repost, and see if you have more questions.

I hope this helps.


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PostPosted: 23 Apr 2021, 21:25 
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Hi, I'm with Suncalc. If you wired it the way you show in the schematic there is no way it can work. BTW the hint on using sockets is on the mark. I do that all the time.

Good listening
Bruce

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PostPosted: 24 Apr 2021, 17:27 
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Attachment:
Prep.pdf
This is the right way for me to use the capacitor from the output of the 5 V power regulator to the power input of the LM 4862 (very tiny in the page). I didn't understand the usefulness of throwing on a capacitor to a direct connection between the power supply and the LM 4862. So I thought inline was the way, discovering by way of a battery tester that connecting the negative end to the power and positive towards the chip allowed current to flow and the opposite way allowed no power to flow. I'm sure I'm not revealing anything to you. I'm not saying Eureka just yet because I looked many times to find current going into the chip (even though it was not provided the right way). No one has criticized the way that C1 0.33uF capacitor (inline) was connected from Audio In.


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PostPosted: 24 Apr 2021, 17:44 
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lame man wrote:
No one has criticized the way that C1 0.33uF capacitor (inline) was connected from Audio In.
That's because that capacitor is connected in the correct way. That is a DC blocking capacitor. It will prevent DC from showing up on the inputs and will allow the AC to pass.

The other two capacitors are filter capacitors which need to be connected across the DC supply to provide filtering. They do this by allowing the AC to pass to ground while the DC cannot.

Does this help?

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PostPosted: 30 Apr 2021, 20:14 
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Attachment:
04_30_21 My amplifier build.pdf
Attachment:
04_30_21 Amplifier with LM386 with socket.pdf
I've remedied what could have been a problem with the capacitors. There is no point in further exploration with this schema. I told sales at Mouser that they could quality check the LM 4862s that they are selling; I ran into a problem with their on/off switches. My objective is to build an amplifier and I have chosen to build one around the LM 386 which is through hole and I can use with a socket. I'm posting the schematic off the internet and my own diagram of how I will build it. Pin 7 (Bypass) is not shown so then I will ground it. The audio input goes through R3 a 10K potentiometer or pot as he refers to it. I viewed every kind of resistor at Mouser and the kind that he has in his head does not match with what Mouser has.


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