My LM7805 Voltage Regulator Heating so much and My logic board cannot turn all the led what is the problem of this guys.

 

Power dissipated as heat = (Input Voltage - Output Voltage)* Current.
No other reason.

 

Power dissipated as heat = (Input Voltage - Output Voltage)* Current.
No other reason.

hey bro i check the fuse switch and power supply and all its good but the circuit. cannot turn all the led? and may voltage regulator heating so much this is possibly a shortage?. sorry this is my first time. learning about electronics

 

Do you get 5V on the output of the 7805? If so, there is no short.
If the 7805 output is at zero, then there is a short.
If it is between 0 and 5V then it is overloaded.

 

Do you get 5V on the output of the 7805? If so, there is no short.
If the 7805 output is at zero, then there is a short.
If it is between 0 and 5V then it is overloaded.

I check the lm7805 and the ouput is 5v

 

I check the lm7805 and the ouput is 5v

What is the input voltage?

 

I check the lm7805 and the ouput is 5v

What is the input voltage?

where i can check the input sir? sorry i'm a newbie i will on the power. supply. to see the input. and check via. multimeter?

 

Left pin = input
Middle pin = 0V
Right pin = output

 

Left pin = input
Middle pin = 0V
Right pin = output

the i/o is same sir almost 5v

 

sir i will ask some question do you have any messaging apps?

 

the i/o is same sir almost 5v

Measure input voltage between left pin and centre pin. Measure output voltage between right pin and centre pin.

 

Looking at the circuit (quite a complex pcb for a beginner) it has 12v AC transforme/bridge/2200u combo feeding the 7805 with approx 16v . On the output 2 X 555, 7474 dual jkff, 2 X 7447 decoder, 2digit 7seg display with 330ohm resistors, and 10 LED on 150ohm resistors. Max current draw if all are on is <400mA, but would typically be ~100mA (5 IC @ 5mA, 7 segments on @ 10mA)

7805 running withtypical push-on heat-sink dropping 11v@100mA would be warm to touch ~ 50degC but OK, at 400mA would be hot >100degC.

I'm guessing there's an assembly fault somewhere, but not a complete short probably. Chip in socket backwards? Solder bridge?

@ferdz have you fully checked every part is in correctly and there are no solder bridges where there should not be?

Maybe post some good hi-res pictures of both sides of your board.

 

Looking at the circuit (quite a complex pcb for a beginner) it has 12v AC transforme/bridge/2200u combo feeding the 7805 with approx 16v . On the output 2 X 555, 7474 dual jkff, 2 X 7447 decoder, 2digit 7seg display with 330ohm resistors, and 10 LED on 150ohm resistors. Max current draw if all are on is <400mA, but would typically be ~100mA (5 IC @ 5mA, 7 segments on @ 10mA)

7805 running withtypical push-on heat-sink dropping 11v@100mA would be warm to touch ~ 50degC but OK, at 400mA would be hot >100degC.
I'm guessing there's an assembly fault somewhere, but not a complete short probably. Chip in socket backwards? Solder bridge?

@ferdz have you fully checked every part is in correctly and there are no solder bridges where there should not be?

Maybe post some good hi-res pictures of both sides of your board.

Yes sir i send a picture later

 

Yes sir i send a picture later

Yes sir i send a picture later

 

The transformer has too high voltage. I wish you had a 8 volt transformer. This will make the 7805 less hot. Please send a picture of the transformer.

 

12v 0 12v 750ma

The transformer has too high voltage. I wish you had a 8 volt transformer. This will make the 7805 less hot. Please send a picture of the transformer.

 

You need to use more flux and heat on your solder connections, they are in pretty bad shape. Cleaning those up may help with your problem.

 

It looks like you have blobs of solder on the input capacitor to the regulator shorting the input and output of the regulator to ground. There is also a very large blob of solder on one wire shorting the regulator output to ground . The output capacitor also looks like it is inserted with reversed polarity. It would help if you posted the schematic with components numbered so we could say for example C1+ instead of input capacitor. Your soldering is so bad around the rectifier diodes that I can't see the tracks.

Les.

 

12v 0 12v 750ma

Are you using the two 12v connections or the 0v and a 12v connection?

 

Are you using the two 12v connections or the 0v and a 12v connection?

0v and 12v connection sir