10 stages of different gains, output voltage is momentarily 1 volt

[Vanclair]

The circuits I'm troubleshooting has a Momentarily output voltage at +1 volt on a good board

The problems with the bad boards is that the momentarily output voltage is not at 1 volt but .800 volts or .600 volts. some are 900 volts, etc.

The circuit has 10 stages of different gains of using LM741 op amps and different IC chips

Which IC chip is causing the momentary output voltage to not be at +1 volt?

What kind of troubleshooting can determine which IC is causing the problem?

I have been replace each IC chip one by one until i find the problem

How would you approach this type of problem?

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The input is a switch and the output voltage rises momentarily to +1 volt on a good board

The Bad boards, output voltage rises momentarily to .600 volts to .900 volts

 

[chuckey]

Without a circuit I can not make a comment, other then was is this "momentary" all about, is it a switch on transient?, is it a desired output? Why have you so many stages of amplification?. Looks like a case of instability to me.
Frank

 

[Vanclair]

The voltage starts at the input of stage#1 at zero voltage and rises up to +1 volt on output stage#10 just momentarily it stays at +1 volt and then discharges back down to zero volts

The problem is which IC op amp or IC chip is causes the voltage not to rise up to +1 volt on the output stage#10

I have to replace the IC's one by one until i find which IC chip is causing the problem

How would you troubleshoot and approach this type of problem?

 

[FvM]

1. Read the circuit schematic
2. Understand the circuit's operation
3. Localize the circuit part that doesn't work as expected

 

[Audioguru]

The ratio of the values of only 2 resistors sets the voltage gain of an opamp. Look at the values and use simple arithmetic to calculate what the output voltage should be with a certain input voltage. Calculate what the output voltages should be for all 10 opamp stages.

Then make measurements starting in the middle by measuring the output voltage from stage #5. If it is wrong then a circuit behind it is bad and if it is good but the output voltage is wrong then the bad part is ahead of it. Another couple of measurements and you will find the bad part.

Please post the detailed circuit schematic.

 

[Vanclair]

Then make measurements starting in the middle by measuring the output voltage from stage #5. If it is wrong then a circuit behind it is bad and if it is good but the output voltage is wrong then the bad part is ahead of it. Another couple of measurements and you will find the bad part.

The voltages from input to output for each stage or IC op amp are not stable voltages

"The voltages rise up momentarily "

The last stage output is 1 volt momentarily and then discharges down to zero

Then make measurements starting in the middle by measuring the output voltage from stage #5.

This only works if the voltage are stable , not rising up or discharging

Each stage , each IC opamps input and outputs are not stable voltages, they are ramping up and down

What kind of troubleshooting would you do to find which IC chip is causing the voltage to be different?

 

[Audioguru]

An oscilloscope will show you the peak voltage of a ramp.
Do you know what is the required peak ramp output from each opamp?

 

[Vanclair]

An oscilloscope will show you the peak voltage of a ramp.

The peak voltage of the ramp is the output, which is 1 volt

Do you know what is the required peak ramp output from each opamp?

No , but how do you find out?

How can i use the O-scope to find out each peak ramp output for each op amp? how many channels would I need for this?

I would have to use a storage O scope

 

[dextermccoy]

PLEASE HELP ME OUT BRIAN OR SOMEBODY ON THIS , I NEED HELP ON THIS

How can i use the O-scope to find out each peak ramp output for each op amp? how many channels would I need for this?

I"M NOT SURE HOW TO GET THE PEAK RAMP output for each IC op amp?

How many 0-scope channels would I need and what else do I need?

 

[betwixt]

Question - is Vanclair and dextermccoy the same person because their questions seem the same and interleaved with each other?

Start from basics. Look at the schematic and see how the stages are connected to each other. Without us knowing how the components interconnect it's difficult to diagnose what the problem is and give advice. For example, if your 10 stages are all DC coupled amplifiers, the error might be very very tiny but at an early stage so the effect is magnified by the voltage gain after it. If your circuit is 10 AC coupled amplifiers, the diagnosis changes completely and I would suggest that one stage is producing a step output and the coupling capacitors were making it look like a ramp. As a circuit with 10 741's is unlikely to be a simple cascade configuration, the chances are it's a combination of the two or has other functional blocks in it, possibly ones that intentionally produce pulses or ramps such as integrators or differentiators.

You will have to give us more information, preferably a copy of the schematic so we can give more advice.

Brian.