Fix Your Stuff Community Store

Options

Beginner PCB Repair - Voltage Regulator Issue

During a fault finding mission on my car I found the Vref on a sensor that should be 5V sitting over 7V. I traced it back to one of the modules and found the pcb mounted voltage regulator was outputting the 7V I'd seen at the sensor. The reg was aLM2931-5.0 fixed voltage regulator in TO-92 config.

In doing some research on the specs I thought it may have failed due to engine bay heat and replaced it with another LM2931-5.0 TO-220. I changed to the TO-220 as it had better heat handling characteristics. The problem is that the new reg is now passing the full 14.5V through. I tested continuity at the pins and there is no shorts.

Has anyone got any ideas why these regs aren't dropping the voltage to 5V as they should? The pins are slightly larger on the second reg and took some force to install. I wondered if I'd damaged it doing this but I thought it that were the case I would see a short between them.

Answered! View the answer I have this problem too

Is this a good question?

Yes No
Score 0
Add a comment

1 Answer

Filter by:
Most Helpful Newest Oldest
Chosen Solution

Options

I suspect you have a damaged component (input/output cap) or pcb that is causing the issue. I would inspect, under magnification, the pcb and test all of the surrounding components with a multimeter.

Another way to isolate some variables is to test the TO-220 regulator on a breadboard, or even with alligator clips considering the simplicity of the reference diagram (Fig. 17 on Page 9 of the datasheet). That way you will know for certain if the regulator is functional.

Was this answer helpful?

Yes No
Score 2
Add a comment

Add your answer

Aileen will be eternally grateful.
View Statistics:

Past 24 Hours: 0

Past 7 Days: 1

Past 30 Days: 2

All Time: 323