weird garbage find..uc3842

[loss1234]

i found a dvd player in the garbage. it had a cool looking power supply. at least i though it looked good as it had +/- 12 volt outputs AND 5 volt outputs.

(it looks similar to this
http://www.flyingpower.com/ProView.asp?ProId=)
BUT this is where i have a question. when i turn it on and hook it up to something like an LED...it pulses. i think its because of the uc3842 which seems to be a PWM controller.


the power seems to turn on and off many times a second! its obviously useless like this for ANYTHING musical so i am wondering why theyd make a supply that would pulse like this.... what is the purpose of a pulsing current source?

just interested. i dont care if i have to put it back in the trash but i am curious.

thanks

[Randaleem]

Hi Loss,

It might be fine. Put a real load on the 5V portion of the supply. Very often these triple output supplies aimed at "digital" uses like computers and DVD's need reasonable current drawn from the 5V supply to properly regulate themselves. In the pulsing you describe, you're probably seeing the supply's attempt to regulate with a lack of adequate loading.

Kind regards, Randal

[loss1234]

hmmm very interesting...thanks for your comments as usual!!