7805 started heating

[Far Han]

i was using a relay control board with 7805 connected. it worked fine for 6 months. now its 7805 started heating. i have changed the 7805 IC but it still heating. its changing 12 V to 5 V. can it be due to malfunction of diode attached to supply or malfunction of resistance attached?
kindly help

 

[milan.rajik]

See if there is any short on the board or any component has shorted. Maybe the shorted component is drawing more current. Does the relays operate properly ?

 

[crutschow]

As noted it sounds like something on the 5V line is drawing excess current.

 

[asdf44]

How sure are you that this is new and what's the expected load current?

A 12V to 5V conversion is extremely inefficient and may start getting warm to the touch between 100-200mA.

 

[crutschow]

Can you measure the 12V current into the 7805?

 

[kam1787]

How sure are you that this is new and what's the expected load current?

A 12V to 5V conversion is extremely inefficient and may start getting warm to the touch between 100-200mA.

Is the board still working?

Is it just one relay?

Did you measure the current and voltages?

 

[Far Han]

thanks all for the replies. i could not come to internet so cant see post. yes there was problem with opto coupler IC attached just before 7805. it was drawing more current.