So I built a very simple power supply circuit with the 1N5408 as my bridge rectifier and the LM323 as my 5V regulator. I have 9V AC as my input, coming from a transformer. The output however is around 0.5V. I have already replaced the LM323 but that didnt fix it. I think that the diodes are the problem (maybe they are used only for higher voltages?). I have read in other places that they should work regardless of the voltage, so I am confused. Does anyone knows what is the problem?

 

Your schematic looks to be OK. The diodes are fine unless you intend pulling 3A.

Are you measuring 0.5V with or without a load?

What is your load?

 

The output however is around 0.5V.

What is the voltage at the power pins of the regulator? This will tell whether the bridge is functioning. The regulator requires some small load to be pulled into regulation. As mentioned, try using a load of some kind such as a 1K resistor.

 

What is the voltage at the power pins of the regulator? This will tell whether the bridge is functioning. The regulator requires some small load to be pulled into regulation. As mentioned, try using a load of some kind such as a 1K resistor.

Weirdly enough Im measuring around 12V between the input and the ground of the LM323. Im going to test the values with load now

 

Correct Weyneh, some regulators require a minimal load, like 20mA or something a bit larger, in order to regulate.

 

Weirdly enough Im measuring around 12V between the input and the ground of the LM323

That's not weird, that is the correct voltage using a 9 vac supply.
I don't see anything in the spec sheet about a minimum load required.
The output of the LM323 has an internal resistance of 2.54K ohms drawing about 2 ma.
Check the pin connections on the chip.
SG

 

That's not weird, that is the correct voltage using a 9 vac supply.

Ohh I see. I checked the values with load and they are the same, 0.5V output and 12V dc input. Well, now I know that the diodes are working, then It has to be the LM323 that is not working, because the connections are all right Thanks !

 

Is the chip getting warm?
Is the .1uf cap shorted?
SG

 

Is the chip getting warm?
Is the .1uf cap shorted?
SG

The chip gets a bit warm yes, and the cap is not shorted. I used tantalum capacitor, so the polarity might be inverted. I put the black marking towards the positive side (according to what I searched)

 

I put the black marking towards the positive side

Tantalum caps usually have the positive side marked as +.
Remove the cap and test.
SG

 

Tantalum caps usually have the positive side marked as +.
Remove the cap and test.
SG

Yeah the circuit is still now working. I will change the 323 and do a few more test. Thanks for the help!

 

Yeah the circuit is still now working. I will change the 323 and do a few more test. Thanks for the help!

Double and triple check the pin-out of the part you are using. I’ve heard of different manufacturers making the same part with different pin arrangements. You need the data sheet from the particular manufacturer. And be sure you can identify the pins with respect to the part’s arrangement. It can be confusing if the pins are shown from above or below. Many manufacturers use a “3D” drawing now to make errors less likely.