Voltage regulator output question

[BRO]

Hi all, fair to say I am new to circuit building, but have been slowly getting some experience.
The question I have is regarding Voltage regs. I am rectifying 26Vac with a 2A bridge rectifier. I get about 23Vdc output. I then connect my 7815CV voltage regulator to the DC output, but I am only seeing 12VDC. I am not sure why, can anyone shed some light on it?
Thanks

 

[KrisBlueNZ]

Hello and welcome to Electronics Point

Start by showing us a complete circuit diagram.

Do you have a smoothing capacitor after the bridge rectifier? Your answer should be yes.

 

[Harald Kapp]

Do you have a smoothing capacitor after the bridge rectifier? Your answer should be yes.

I guess the answer will be no. That explains the 23V DC measured and the irregular behaviour of the 7815.

Also a pair of decoupling capacitors (100nF each) from input to GND and from output to GND will help the 7815 to work stable.