LM78L05 not regulating properly

[xorophone]

Hello! I recently finished the Leviathan delay from Etcher's Paradise, but it didn't work. I'm now in the process of fault diagnosing and I realised that my LM78L05 voltage regulator doesn't reduce my voltage. I realised that the ground wasn't connected properly so I fixed that. Still didn't work though. I thought it was broken so I tried it with a new LM78L05 outside of the circuit (connected + from power supply to LM78L05 input and - from power supply to LM78L05 ground and then checked the voltage between ground and output and compared it to the voltage between ground and input). Still doesn't regulate it to 5v. It seems like both of them reduce the voltage by about 1 volt, but not more than that. Please help me!

I'm giving it 9v, 500mA but it measures ~8.87v. My multimeter doesn't want to measure the mA right now for some reason.

Edit: My multimeter measures ~8.16v after it has been regulated, but on the other regulator it was a little under 8v.

[Matt]

Post a couple of pics when you get a chance

[m-Kresol]

Did you connect the output of the new regulator to something? It is very well possible that you'll only get 5V when under load.
I guess you checked the datasheet for correct pinout?

[xorophone]

Post a couple of pics when you get a chance

Here's some pictures of how I wired it when I tested it:





It's pretty much impossible for me to take a picture while I'm measuring it with the multimeter, but I put the black lead on the middle pin of the regulator and the red lead on the pin that isn't connected to anything (the one to the far right on the first picture.)

When I took these pictures I realised two things that you might have to take in to consideration:

• On the regulator it says "L78L05", not "LM78L05" like I said before, but that's just the brand or something, right?
• My power supply only outputs 500mA from all of the 9v ports combined (there's 8 of them.)

Please tell me if you need pictures of something else.

Edit: If the images aren't showing up, try right clicking the little image-icons and pressing "Open image in new tab".

[madbean]

Picture not showing. Anyway, if it is 78L05 the pinout might be opposite. Try flipping it around on the PCB.

[xorophone]

Did you connect the output of the new regulator to something? It is very well possible that you'll only get 5V when under load.
I guess you checked the datasheet for correct pinout?

The pinout is correct.

Nope, I only connected it to my multimeter, but the other one was connected to a few capacitors and resistors and of course the PT2399, but it did the same thing. I might even have destroyed two PT2399-chips because I gave them 8v instead of 5.

Take a look at the pictures in my other post to see how I connected it while testing.

[xorophone]

Picture not showing. Anyway, if it is 78L05 the pinout might be opposite. Try flipping it around on the PCB.

Try right clicking the small image-icons and pressing "Open image in new tab". I don't know how to make the images show up correctly.

Interesting. I will try that. Thanks.

[madbean]

Definitely backawards. Look at the picture of the traces in the doc. Where you have 9v connected to your regulator is the pin that goes to the PT and should be 5v.

[xorophone]

Definitely backawards. Look at the picture of the traces in the doc. Where you have 9v connected to your regulator is the pin that goes to the PT and should be 5v.

I tried turning it around but it did the same thing. Have I killed it?

I'm looking at this datasheet: http://www.st.com/content/ccc/resource/technical/document/datasheet/15/55/e5/aa/23/5b/43/fd/CD00000446.pdf/files/CD00000446.pdf/jcr:content/translations/en.CD00000446.pdf

If you look at the "Pin configuration" page it looks like the way I connected it first is right. On the pictures I posted the flat side of the regulator is facing the camera.

[m-Kresol]

the ones you have need to be flipped 180° from what the build doc says. The lower square pad is the input, i.e. pin 3 (the left one if you look at them from the front).

[xorophone]

the ones you have need to be flipped 180° from what the build doc says. The lower square pad is the input, i.e. pin 3 (the left one if you look at them from the front).

Forgot to mention that I'm building it on a perfboard so I'm only using the schematic. Seems like I've connected it correctly before, but I will try putting it in my circuit again. I've got a pack of 100 78L05 from China on its way so if this doesn't work I think I'll wait for those. They're not the same brand and probably more like LM78L05's. I bought these L78L05 regulators here in Sweden, so I expected them to be better than cheap chinese ones, but maybe not. We'll see.

I does take some time for that package to arrive though, so if my patience runs out, will I be able to buy some UA7805 voltage regulators at a local electronics shop and use those instead? I know they're overkill, but will they work without replacing any other components in the circuit?

As I said, I'll try it in my circuit one more time (making sure it's facing the correct way), but this is my last one before the package from China arrives.

[m-Kresol]

78L05 and LM7805 are different packages and have flipped pinouts, iirc. Check the datasheet to make sure you put the ones you get in the right way.

[xorophone]

the ones you have need to be flipped 180° from what the build doc says. The lower square pad is the input, i.e. pin 3 (the left one if you look at them from the front).

Seems like I've connected it correctly before, but I will try putting it in my circuit again.

Very interesting... I put it in the circuit again and now it seems to measure about 7 volts after it's been regulated instead of 8. I definitely put it in the right way this time. I checked the datasheet multiple times. I actually turned it on with a PT2399 in the socket to see if the voltage got regulated to 5 volts. It didn't. When I plugged it in to an amp I got a weird repeating noise (like noise with delay on) which changed as I turned the pots. It didn't react to my guitar signal. I'm guessing this comes from the high voltage or the fact that it's dead because I've given it too much voltage before.

I actually think I'll go and buy a 7805 tomorrow and try using that. I really want to get this pedal working as soon as possible. I'll replace the chip when I'm sure I'm getting 5 volts too.

[xorophone]

the ones you have need to be flipped 180° from what the build doc says. The lower square pad is the input, i.e. pin 3 (the left one if you look at them from the front).

Seems like I've connected it correctly before, but I will try putting it in my circuit again.

I actually think I'll go and buy a 7805 tomorrow and try using that. I really want to get this pedal working as soon as possible. I'll replace the chip when I'm sure I'm getting 5 volts too.

I bought a UA7805 and put it in my circuit. Worked great. The chip is getting 5 volts now. The pedal still doesn't work, so my fault diagnosing continues, but if I need any more help I'll start another thread.