hello people....got a 5v regulator (7805) input pin 8v....output is 5v without load....once i connect load input then drops to 5.3v and output to 3.9 ....could the regulator be faulty? or leaky caps ..any ideas would be much appreciated thank you..cheers

 

Hi.

How about some schematics, with cap values? What is your load?

 

This seems obvious, but the local capacitors are necessary to prevent oscillation. Leaving those out always results in unexplainable output voltages.

and specify the exact part number you have. They all require different local capacitor sizes.

 

Also how far is the load removed from the regulator?
Max.

 

Hi.

How about some schematics, with cap values? What is your load?

its an audio equipment all that it drives is a prom IC and two 7 segment displays..

 

This seems obvious, but the local capacitors are necessary to prevent oscillation. Leaving those out always results in unexplainable output voltages.

and specify the exact part number you have. They all require different local capacitor sizes.

Hi AAA....its seems to be a pretty straight forward circuit all it drives is an prom IC and two 7 segment displays...

 

Also how far is the load removed from the regulator?
Max.

Hi Max...it is connected by a foot long cable..and all its driving is a Prom IC and two 7 segment displays

 

will try the caps tomorrow..probably also mite put in a new 7805...will share the results with you guy....thanks for your input....cheers

 

hello people....got a 5v regulator (7805) input pin 8v....output is 5v without load....once i connect load input then drops to 5.3v and output to 3.9 ....

If the input drops to 5.3V then the input supply voltage is apparently being current limited. What is supplying the 8V?

 

You may check the current ratings of the supply you are using....or otherwise try changing the supply.

 

If the input drops to 5.3V then the input supply voltage is apparently being current limited. What is supplying the 8V?[/QUOTE


the 8v is supplied from a transformer directly...

 

will post a schematic this evening ...thanks guys.

 

the 8v is supplied from a transformer directly...

Then your transformer apparently is not large enough to supply the load current.

 

hello everyone...the problem i had with 5v droping was finally fixed...i had a series bulb connected to the mains of the mixer ...guessing that was the reason the moment i plugged the equipment directly into mains it all came good....was the current insufficient ??

 

thanks to you all who gave me clues...ta.