| Electronics > Beginners |
| L200 and UA741 |
| (1/2) > >> |
| mike_mike:
Dear Forum, I built the attached schematic on a home made PCB. When there is no load on the output, the output voltage varies from about 2.77V to 30V. But when I connect a load (12V, 20W bulb), the output voltage goes down to 0.14V and the current is about 0.18A. If I rotate the 100K potentiometer there nothing is happening. I also noticed that the UA741 is heating up while the load is connected. I also checked the PCB and there are no bridges. What should I do to make this project working ? More details: input voltage about 40Vdc, output varying between 2.77 and about 30V, the voltage on the 0.1ohm resistor while the load is connected is 0.02V. |
| Hopkins:
Do not know how to help me? About the knowledge I'm looking for, I'm following up on sharing this information. |
| mike_mike:
Please delete this topic. The project has been abandoned. |
| bson:
What's the input voltage? What happens if you use say a 1k resistor load? |
| mike_mike:
I am using a 24V/160VA power transformer. If I use as load an 1K resistor and if the output voltage is 25.1Vdc, then the voltage does not drop. If I am powering a 24V/40W light bulb, the output current is 0.36A, and the ouput voltage drops to 0.7V. I also obtained the following voltages: 1. LM741 a.pin 7 to pin 4 no load = 31.2V load = 29.9V b. pin 2 to 3 no load = 1.1mV load -1.172V - with 100k pot completely in one direction c. pin 2 to 3 no load = 1.1mV load -43.9mV - with 100k pot completely in other direction 2. Voltage across R3 no load 0.3mV load 34.8mV 3. L200 a. pin 5 to GND no load 25.1V load 0.8V b. pin 2 to GND no load 24.8V load 2.0V I attached the layout for this power supply. I also checked with a new 741, and the power supply is still not working correctly. |
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