compaq cq20 no power

[tzoupkas]

Re: compaq cq20 no power

Please check for short in +3VS rail, but in my opinion check for short on any rail related with U18. U18 might be 90% off, when U1 is false.

[sasser]

Re: compaq cq20 no power

now my motherboard got power on 1.3000A but still no display. i almost done this case. still try troubleshoot why no display at this stage. need to reprogram bios? and how about standby power is starting 0.1280A then drop to 0.0460A before power button press. after power button is press got 1.3000A.
1.300A still not coming display. what i need to checked this motherboard also have tokin OE128.

[tzoupkas]

Re: compaq cq20 no power

Wait! first things first, stay calm. What did you changed on the mobo?

[sasser]

Re: compaq cq20 no power

i just changed lm393

[tzoupkas]

Re: compaq cq20 no power

I see. When you plug your power adapter measure the voltage at coil L1 it must be near DC jack. Don't press power button just see the measurement and see if it ripples lets say between 18,4V and 19,5 volts. Do that for start and we will see later.

[sasser]

Re: compaq cq20 no power

I see. When you plug your power adapter measure the voltage at coil L1 it must be near DC jack. Don't press power button just see the measurement and see if it ripples lets say between 18,4V and 19,5 volts. Do that for start and we will see later.

both side i got 19.16v sir.

[tzoupkas]

Re: compaq cq20 no power

Stable 19.16 Volts?

[sasser]

Re: compaq cq20 no power

Stable 19.16 Volts?

yes stable on 19.16v

[tzoupkas]

Re: compaq cq20 no power

Check voltages at KBC U18 in your case. Especially the +3VAL and +3VAL_KBC see if they are 3V and check with your finger if it is getting unusually hot.

[sasser]

Re: compaq cq20 no power

Check voltages at KBC U18 in your case. Especially the +3VAL and +3VAL_KBC see if they are 3V and check with your finger if it is getting unusually hot.

3v is ok. yes u18 is KBC getting unusually hot. need to changes ? or check around ? i measure caps around some 3v and some 1.78v. is normal

[tzoupkas]

Re: compaq cq20 no power

yes changed it without second thought, as I said 90% KBC is off in such cases, changed it and board will come in life straight away.

[tzoupkas]

Re: compaq cq20 no power

When you will remove the KBC plug power, measure again the voltages if voltages are not normal then check for short in caps but you will not need it. Hope I helped you.

[sasser]

Re: compaq cq20 no power

U means im remove that kbc then measure standby current? Why the current not stable. From 0.01280 drop to 0.0460a? Its related to kbc? I will remove and mention the results here. Thanks u helped me a lot. In this case for anotger compaq if no voltage means check all mosfet near dc jack. May be might burn in small signed.we not noticed that happen

[tzoupkas]

Re: compaq cq20 no power

No standby current, just voltages near KBC must be 3Volts. As for the other compaq you said make a new post and me and the other guys will help you. If you have the compaq in front I can help you now but in a new post. Thank you.

[sasser]

Re: compaq cq20 no power

No standby current, just voltages near KBC must be 3Volts. As for the other compaq you said make a new post and me and the other guys will help you. If you have the compaq in front I can help you now but in a new post. Thank you.

Friend any suggestion before i remove the kbc? Coz i dont have the new one. Before remove can i checl the caps near kbc. Maybe hav shorted or leakage

[tzoupkas]

Re: compaq cq20 no power

Even if it so (shorted caps) KBC is already dead. Change KBC, measure voltages, then check caps. My opinion I have done this many times never had issue with caps near KBC.

[ktmmotocross]

Re: compaq cq20 no power

...

[sasser]

Re: compaq cq20 no power

after remove i have check 3v around kbc the power is normal then need to order from china to get new one smsc kbc 1091 ic.

[tzoupkas]

Re: compaq cq20 no power

yes order the kbc and place it.

[sasser]

Re: compaq cq20 no power

done replace new kbc. but my laptop still cant power on. check cap near kbc some 3v and some 1.7v. before replace kbd got power on 1.300A now cant power on and got only 0.0203A. try solder each pin kbc maybe not fit on pads. but still cant power on.

result on kbc pin. check +V3AL involved pin 14,39,58,84,106,119 got 3v but check on +3VS pin 49 no volt ,15 1.78v ,68 3.18v
reference page shematic on pages 43

checked kbc_pwr_on i have checked Q34 got power from 5V on pin 1 but 2&3 no volt Q35 only pin 2 got 5volt. Q28 pin 2got 5v the no volt. ref (pages 7)