Using power supply to start CQ71

[6ot4hr]

Hi guys, a friend brought me Compax CQ71 without charger, i see it has a round charger plug with the middle pin inside but since i don't have a charger will it start or at least charge up a battery it connected to 19V power supply?

Or is it possible ti feed it 19V to motherboard to start?

Charger looks like this:

[goontron]

Re: Using power supply to start CQ71

It will charge, but it will error out on boot, probably run throttled. 1 and 2 are ground and power respectively, 3 is part of the "one wire" data circuit. Its better to not leave that floating, so a ceramic cap and a 1k resistor in series from 3 to 1 is a good idea. 19v at 4 or 5A should do.

If you go to the board itself, ground (1) goes to the two black wires on the charging socket loom, and 2 goes to the two red wires. You can ignore the other two. One runs the charging LED, the other the "one wire".

[6ot4hr]

Re: Using power supply to start CQ71

It will charge, but it will error out on boot, probably run throttled. 1 and 2 are ground and power respectively, 3 is part of the "one wire" data circuit. Its better to not leave that floating, so a ceramic cap and a 1k resistor in series from 3 to 1 is a good idea. 19v at 4 or 5A should do.

Thanks Goontron, will try it now that you brought some insingt... Have a good one, cheers!

[piernov]

Re: Using power supply to start CQ71

goontron described a behaviour that happens on Dell laptops for sure. I don't even think the battery will charge.
For newer HP laptops (those with the smaller barrel plug, blue at the end), a voltage on the center pin is needed for the laptop to turn on (and even have the LED light up). I've had success with connecting a resistor from +VIN to AD_ID pin of a few kohms, but a proper voltage divider is a way better idea since that voltage will go into the EC : it'll not like having 19V there (there should be a protection diode but don't rely on that). You'll need to figure out what's the needed voltage, maybe a couple of volts.
For older ones (HP/Compaq, the one you have for example) I can't remember how it behaves, maybe as goontron described.

[6ot4hr]

Re: Using power supply to start CQ71

goontron described a behaviour that happens on Dell laptops for sure. I don't even think the battery will charge.
For newer HP laptops (those with the smaller barrel plug, blue at the end), a voltage on the center pin is needed for the laptop to turn on (and even have the LED light up). I've had success with connecting a resistor from +VIN to AD_ID pin of a few kohms, but a proper voltage divider is a way better idea since that voltage will go into the EC : it'll not like having 19V there (there should be a protection diode but don't rely on that). You'll need to figure out what's the needed voltage, maybe a couple of volts.
For older ones (HP/Compaq, the one you have for example) I can't remember how it behaves, maybe as goontron described.

Yeah piernov, it doesn't start or charge battery. Power led on the bottom of the laptop just blinks 3 short 1 long blink and nothing happens (withouth middle pin connected).
Current draw is 20mA

I saw on some site that it needs 13.5 V on smart pin to recognise a 65W charger, and full 19V on smart pin to think its the 90W one... Will try to do that and see it it smokes Stay tuned!

[6ot4hr]

Re: Using power supply to start CQ71

Success,

Using 190kOhm from +19V to smart pin seem to do the trick, laptop boots but no picture is shown. At least i can troubleshoot now Thank you all for your help!

[goontron]

Re: Using power supply to start CQ71

For older ones (HP/Compaq, the one you have for example) I can't remember how it behaves, maybe as goontron described.

I was basing that off of the CQ57 i had a long time ago, so fairly low end and old. I wouldn't be surprised to see it not even have a proper charger detect circut installed, unlike OPs machine.

Glad to hear you get it working 6ot4hr.

[6ot4hr]

Re: Using power supply to start CQ71

I was basing that off of the CQ57 i had a long time ago, so fairly low end and old. I wouldn't be surprised to see it not even have a proper charger detect circut installed, unlike OPs machine.

Glad to hear you get it working 6ot4hr.

No problem goon, you did help alot and pointed me in the right direction... Now to fix the black screen and we are golden...

[6ot4hr]

Re: Using power supply to start CQ71

Fixed. It's back in it's working order and saved from dumpster
TYALL!

[vtfe]

Re: Using power supply to start CQ71

@6ot4hr: How did you fix the black screen? Same problem here. CQ71 starts, but blank screen and steady caps lock led. Please advise.