motherboard power issue

deafroadrunner

heres a strange one i'm having
my laptop isnt turning on at all. now the charging port cable is reading the 19volts and if you test the 4 connector pins on the board for continuity it exists between the positive to positive and negative to negative. and there is no short between positive and negative
but if test the same 4 pins on the board for power there isnt any.
any ideas




http://imgur.com/a/PU2iA

http://imgur.com/a/jHNna

sKeith

Can't view imgur in work

deafroadrunner

should work now i've included them as attachments

sKeith

deafroadrunner wrote: »

heres a strange one i'm having
my laptop isnt turning on at all. now the charging port cable is reading the 19volts and if you test the 4 connector pins on the board for continuity it exists
but if test the same 4 pins on the board for power there isnt any.
any ideas

This suggests you are saying that there is a short between v+ and ground,
can you clarify, you are reading short between pin1 -pin2 , also , pin1 -pin3, and pin1 - pin4. Short as in 0 ohmns. (with charger removed, test it unplugged)

deafroadrunner

sKeith wrote: »

This suggests you are saying that there is a short between v+ and ground,
can you clarify, you are reading short between pin1 -pin2 , also , pin1 -pin3, and pin1 - pin4. Short as in 0 ohmns. (with charger removed, test it unplugged)

sorry i should of explained that better
there is no short between positive and negative. ive continuity on the negative pins with only negative pins and same for the positive ones

sKeith

With all plugged in. and volt meter set to read voltage.
power plug [pin1 black pin2 black pin3 red pin4 red ]
voltmeter black on pin1; with voltmeter red, test for voltage on pin3 or pin4. what volts are you seeing?

deafroadrunner

sKeith wrote: »

With all plugged in. and volt meter set to read voltage.
power plug [pin1 black pin2 black pin3 red pin4 red ]
voltmeter black on pin1; with voltmeter red, test for voltage on pin3 or pin4. what volts are you seeing?

it varies from from 15.6mv to 30 mv

sKeith

deafroadrunner wrote: »

it varies from from 15.6mv to 30 mv

So, 0v then. we would really like to see 19V here.
So far this looks like the motherboard has a short somewhere.

I'll just double check this with you. when unplugged, and you test power adapter plug, you see 19V, but once inserted and tested we have 0V.

Do you have a 2nd power adapter or a bench power supply to verify. Its possible that power adapter can be bust and still show a supply of 19V with no current being drawn, but as soon as you try to pull current it sinks to 0V.

sKeith

deafroadrunner wrote: »

it varies from from 15.6mv to 30 mv

FYI.
15.6mV to 30 mV is same as 0.0156V - 0.030V
For our tests here, we want to see full V's as in 1V or 19V (deal with the numbers to left of decimal point)
we can ignore these mVs readings as measurement errors

deafroadrunner

sKeith wrote: »

So, 0v then. we would really like to see 19V here.
So far this looks like the motherboard has a short somewhere.

I'll just double check this with you. when unplugged, and you test power adapter plug, you see 19V, but once inserted and tested we have 0V.

Do you have a 2nd power adapter or a bench power supply to verify. Its possible that power adapter can be bust and still show a supply of 19V with no current being drawn, but as soon as you try to pull current it sinks to 0V.

this was basically it. ive retested the charging port ribbon again on its connected to the mains. doesn't seem to working to be reading a voltage maybe that was the fault, gonna get a new one and try.
there isnt anything wrong with power supply as it works perfectly in my other laptop.

ED E

If you're getting 19v off the PSU and no further theres most likely a failed SMC somewhere. Now you're into board repair territory.

deafroadrunner

I'm thinking it has to be the DC jack now as when testing the end that connects to the board the 19v volts can be intermittent. I don't think it's the board.