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Troubleshooting circuit with Multiple power supply

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dann11

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Hi, I have designed a circuit using using op-amps, comparators, diodes and transistor. It uses 15 and 5 volts supply, but during my test I have accidentally supplied 15V for the whole circuit system, and after that the two supply inputs appears to be shorted. Whenever I applied the two supplies together, the 5 Volts power supply is pulled up to 15V. As I do connection test, there is no physical contact in between the two supplies. I also tried to input them separately, and I have noticed that everytime I supplied the 15V, the circuits that is powered by 5V is also powered up but with only 2V present in each circuits. What might be the problem with my design? hope you can help me with this..


feedback.jpg
 

You probably applied 15V to the output of the 5V regulator that probably destroyed it. Replace the 5V regulator.
 

Audioguru said:
You probably applied 15V to the output of the 5V regulator that probably destroyed it. Replace the 5V regulator.
Click to expand...

I haven't used any regulator yet, I only used an external power supply, and yes I have accidentally connected the 15V supply to power line of the 5V circuits.
 

We would have to see the circuits to assess any damage that might be cause by excessive voltage. It isn't unusual to see some 'leakage' between supplies on one part of circuit being seen elsewhere but exactly how much to expect and whether the paths are prone to damage would depend on the components and how they are connected.

Brian.
 

I'm thinking the same as Brian.
Most likely several devices in the 5 volt circuit became damaged. It could be a single IC, it could be all of them.
The bottom line is that once it happens you get leakage all over the place.
 

I have again checked the components under the 5V supply, I supplied it with 5V while leaving the 15V circuits unpowered, and everything seems to be working perfectly well. But once I supplied the 5V and 15V together, still the 5V supply is pulled up to 15V, I am really confused on which part is defective or damaged.
 

If you post the schematic then we can show you what might be wrong or how to measure the circuit to find what is wrong.
 

I'm with Audioguru on this one.
Without schematics all we can do, is to speculate to the end of the world and not reach any conclusion.
 

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