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Problems with LM317 Regulator Circuit

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Muhammad Nasar:
I had made this circuit to make a powersupply which can supply voltage upto 21 volts, i have made the circuit but there is an unusual problem with it i.e.  i get the desired voltages on the output but as soon as i connect a 80mm computer fan to it the voltage dropsdown drastically and fan doesn't run, i set it to 12 volts but when i connect the fan the voltage got droped down to 3 volts and even by adjusting the POT's Nobe to increase voltage , nothing happen the voltage remained the same. But when i disconnected the 2200uf Cap the circuit ran fine but still there was the voltage problem i.e. i set the voltage to 12volts but when i connected the fan it droped to 6 volts. I then connected the 1000uf cap instead of  2200uf after bridge rectifier and the same condition repeated that i was getting voltages at the output but as soon as i connected fan to it it droped and fan didn't run.
Plz help me as i am very new to electronics and have started my Electrical Eng. at the university. here is the schematic
http://img192.imageshack.us/i/image0004.png/  

mikemxyzzy:
What is the voltage going in to the LM317? Maybe the transformer is less than 24VCT.

Muhammad Nasar:
I have checked it with the mutimeter it's 24 volts DC

Alex:
Can the transformer supply enough current?

For powering a fan, you can use an LM7812 in place of the LM317 and get rid of every other component apart from a small 1uF output capacitor and a 470uF input capacitor.

qno:
Does it work without the Fan?
Can you control the voltage wit a lighter load?
What is the load of the fan. Depending on the model the LM317 can supply 100, 500 or 1500 mA.
Maybe the LM317 is in current limiting mode.

The 100uF looks a bit large, is it for soft start?
Remove this for test.

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