What is the reason to zap bees? They are amazingly useful creatures....

 

I'm using the potentiometer to control the supply voltage (~30 volts coming from the 6009 module) to the op-amp thus controling the magnitude of the output signal.
The led illuminate once I release the output through S1 and its getting a minimum 9 volts (in series with the 10k resistor) so it's working fine, no problem there.
The output node is connected to a sort of zapping grid.

I have not seen the use of varying a supply voltage to vary the output of an opamp previously, EVER! Usually the output of an opamp is adjusted by varying the gain. Also, the 741 device is a relic, over 30 years old.
At the very least the power input to the 741 should have capacitors between the positive supply connection and the negative supply connection. Probably 0.47 mfd and also perhaps 10 mfd in parallel.

 

What is the reason to zap bees?

I'm guessing it's to extract venom, for medical use, without killing the bees.

 

I have not seen the use of varying a supply voltage to vary the output of an opamp previously, EVER! Usually the output of an opamp is adjusted by varying the gain. Also, the 741 device is a relic, over 30 years old.

Thanks for saying out loud what has been on my mind while reading this thread.
I actually meant to write a reply similar to yours, but since the only thing that happens in these situations is that a random internet stranger becomes upset at me, I decided to wait on the sidelines to see how far this preposterous idea would go.

 

Thanks for saying out loud what has been on my mind while reading this thread.
I actually meant to write a reply similar to yours, but since the only thing that happens in these situations is that a random internet stranger becomes upset at me, I decided to wait on the sidelines to see how far this preposterous idea would go.

The fact that this is a lousy way to do things was pointed out early on, but it became apparent that there is no interest in doing things well, only in sticking with the current approach, despite it not working reliably.

 

I must admit, my immediate reaction when I read the initial post was "Why is he using an analogue op-amp to amplify a digital signal?" Maybe I'm missing something, but surely it just needs a simple transistor or MOSFET, driven by the input voltage and connected to a variable PSU to give him the required variable output voltage. Occam's Razor?

 

The circuit used to work ok. Then it stopped working ok.
Is the circuit built on a solderless breadboard/protoboard?

 

the 741 device is a relic, over 30 years old.

Well over.
How about 56 years.
It was released in 1968.

 

The maximum continuous output current of the 741 is rated as 25mA and the maximum dissipation is rated as 500mW. If you are supplying 32V to the chip and on some occasion its output was inadvertently short-circuited, the chip would have been dissipating 32V x 25mA = 800mW and could have been damaged.

That's my guess too, but what's confusing is that I can still control the output which implies that it is responsive but just not reaching its previous maximum. Can that be?

 

The circuit used to work ok. Then it stopped working ok.
Is the circuit built on a solderless breadboard/protoboard?

No, it's final built on a PCB

 

Well over.
How about 56 years.
It was released in 1968.

He's a good old fellow, still alive n kicking

 

Can that be?

Yes, if the chip has been damaged.

 

I'm guessing it's to extract venom, for medical use, without killing the bees.

You guessed right

 

What is the reason to zap bees? They are amazingly useful creatures....

It's to extract venom for medical use without killing the bees

 

That's my guess too, but what's confusing is that I can still control the output which implies that it is responsive but just not reaching its previous maximum. Can that be?

Last update, I replaced the 741 with a brand new one... still no change, so now I'm even more confused. All the measurements around the circuit are as designed except the final output which was working before!!!!

 

Check for a dry joint where the two resistors provide feedback to the inverting input of the 741.

 

Probably a very useful diagnostic act will be to measure the voltages supplied to that op-amp, and let us know what they are now.
Also, showing us more of the circuit may quickly reveal where the problem lies.
FAR TO OFTEN we are only shown a small segment of a circuit, based on the guess by the TS, that the problem must be there because that is where they have decided it is. And usually the problem lies in the portion that we have not been shown.
In these forums there is a VAST collection of wisdom from a very large number of very experienced people willing to share insights. So presenting more of the circuit, maybe even all of it, will not confuse them at all.

 

I'm boosting a square signal (non uniform) View attachment 329113with op-amp LM-741C. Supply voltage is variable up to 30 volts to control the amplitude of the output signal.
The circuit was working fine for many months now and I was getting the output signal up to 27 volts p-p. Suddenly the output dropped and I can only get a max amplitude of 16 volts from it?!
Any idea what could be the reason?
Is the op-amp damaged in any way?
Note that changing the supply voltage is still affecting the output but can't reach its previous top value of 27 volts.
Also note the input signal is around 11 volts p-p

The Op Amp is operating in a Linear Mode.
If the circuit ws performing as expected earlier,
Either the Supply voltage to Pin 7 has dropped or the input to a lower value or the input to pin 3 has dropped in amplitude.