LM338K not being able to provide current


2016-05-05 3:23 am
hello everybody, I have some ripple issues in my diy audio power amp, so I decided to use a lm338k as a regulator, and built the circuit in the air, old style, as I was sure I could connect everything as per the circuit in the datasheet, including the two protecion diodes. now, it works, and regulates from 2.6 to 37V (input is 40v), but the weird thing is that this power supply is unable to provide current, the transformer is capable of at least 5A and my first test was to connect some LED with a 2k resistor, fine, it works, measuring voltage the regulation took place, now, for the current test I got a 8 ohms 10W resistor and set the power supply to 8V, I was expecting a little drop in the voltage under load and be able to measure 1A, but no, it goes all the way down, to zero, or close. if anybody has any ideas please let me know, as I'm puzzled by the issue. I can post pics and the circuit, I think you'all are familiar with this regulator.