Hello,

I have a 741 Op Amp circuit with a +ve supply voltage of 15V and a negative supply voltage of -15V. When I connect the circuit to compare
the voltages at the inputs, the LED display on the PSU supplying +15V drops to around 4V. The display on the other PSUs do not change. Does this
indicate a problem ? Does this mean there is a fault somewhere or is it normal ?

Thanks

PJ

 

When I connect the circuit to compare
the voltages at the inputs, the LED display on the PSU supplying +15V drops to around 4V. The display on the other PSUs do not change.

Post a schematic.

Do you have current limiting set on the positive supply? What is the current being drawn when the voltage drops?

 

"" Does this indicate a problem ? ""

Obviously, it does indicate a problem.
Probably that You are measuring things incorrectly.

Pictures and a Schematic would help immensely.
.
.
.

 

"" Does this indicate a problem ? ""

Obviously, it does indicate a problem.
Probably that You are measuring things incorrectly.

Pictures and a Schematic would help immensely.
.
.
.

Thankfully I've found the fault: The PSU supplying input voltages to the amp was not grounded properly. The displays on the PSUs seem to be behaving themselves now.

 

Please keep in mind that with the +-15 VOLT SUPPLY THE 741 opamp is only good for +- ten volts out. It is a rather antique circuit. It still works BUT ....