Acer Aspire 5735Z power circuit in dc problem help!

Can anyone help me for the acer aspire 5735z when i use dc jack the battery charge well but when i open the laptop and about 2minutes to 5 minutes it shut down unintentionally but sometimes i repeat it 10x above its work well! and i check the cpu thermometer its good 45c to 50c so i decide to check the dc adaptor in my multimeter it says 18.99v i know that's good cause its closes from its proper voltage 19v even when i jiggle it dc adaptor is good then i go to dc jack i test says 18.99v perfectly much to adaptor voltage but right beside on the dc jack i see small triac and i test it says 18.50v i dont know if that was the problem. but i'm pretty sure that the problem is in the power circuit on the acer aspire motherboard cause when i use the battery 12v is turn on! help me to solve my problem thanks for reading!

It's common for the DC power jack to be vulnerable to physical stress. Hairline cracks can develop in its solder joints.

These might be okay when cool, allowing it to power up. But then as components heat up the connection goes bad.

Just speculating. Does the power light show the unit is going back and forth between AC power and battery power?

Can you wiggle the power cable, and cause it to malfunction? Etc.

The dc cable is has good connection whether i wiggle it its always 19v