38v adapter output analysis

[rajaram04]

Hello everyone

I hv an adapter of old china made cheap external T.V. tuner card & parameter on the unit is given as 38v 100mA

But with open circuit condition when i connect voltmeter the reading shows 55v approx

So how it is ? Is it corrupted or its due to some rules as per load at output ?

 

[E-design]

Many cheap older adapters were unregulated and output voltage is specified at a certain load.

 

[Audioguru]

I have a cheap Chinese wall wart that is rated at 9VDC/100mA and when the load is 100mA its output is exactly 9VDC with only a little ripple. But without a load its output is close to 18VDC. Its windings have thin cheap wire that has resistance.

 

[rajaram04]

I have a cheap Chinese wall wart that is rated at 9VDC/100mA and when the load is 100mA its output is exactly 9VDC with only a little ripple. But without a load its output is close to 18VDC. Its windings have thin cheap wire that has resistance.

i see so thats the nature hmm

ok what if i connect LM 317 at my output here ?

i mean to get output as per my use & all that . . !!!!

is it a good idea ?

 

[Audioguru]

You can use a voltage regulator IC if the minimum input voltage for its output voltage is high enough. My cheap wall wart with the very poor voltage regulation gets hot when it has a load and even when it has no load so it wastes power.