PCB soldering damage

[Input Nirvana]

What setting should I be on with the multimeter?

[bluecar5556]

Volts DC
__
---
20 Range

Note: (2) range may have better resolution

[Input Nirvana]

That's what I thought. No voltage from Pin 1 (indent) and Pins 6, 7, 8.

Pins 2, 3 IN have 5.15 volts

[bluecar5556]

1)Test between U4 pin 1 (GND) and U4 pins 2 & 3 = 5VDC

1) your reading=

2) If not, test between any GND/shielded GND AND U4 pins 2 & 3 = 5VDC

2) your reading=

If not, power down and unplug PSU

3) Switch meter to Ω, test between U4 pin 1 (GND) AND any GND/shielded GND = 0Ω

3) your reading=

[Input Nirvana]

1)Test between U4 pin 1 (GND) and U4 pins 2 & 3 = 5VDC

1) your reading=  5.15

2) If not, test between any GND/shielded GND AND U4 pins 2 & 3 = 5VDC

2) your reading=  5.15

If not, power down and unplug PSU

3) Switch meter to Ω, test between U4 pin 1 (GND) AND any GND/shielded GND = 0Ω

3) your reading=

These are the readings in bold

[bluecar5556]

3) Switch meter to Ω, power off computer, test between U4 pin 1 (GND) AND any known good GND/shielded GND = 0Ω

your reading= Are you getting ∞ (infinity) aka (OFL) Out Of Limits, (OL) Open Loop, no continuity?

If the reading is 0Ω, suspect U4.

If the reading is ∞, bridge U4 pin 1 (GND) to known good GND / Shielded GND with wire and re-test.  

Switch meter to VDC (2), test between U4 pin 1 (GND) AND U4 pins 6, 7 & 8.

You should now be getting 5V

[Input Nirvana]

3) Switch meter to Ω, power off computer, test between U4 pin 1 (GND) AND any known good GND/shielded GND = 0Ω

your reading= Are you getting ∞ (infinity) aka (OL) Out Of Limits, (OL) Open Loop, no continuity?

If the reading is 0Ω, suspect U4.

There is continuity, and it's at 2.2 on the 200 scale

If the reading is ∞, bridge U4 pin 1 (GND) to known good GND / Shielded GND with wire and re-test.  

Switch meter to VDC (2), test between U4 pin 1 (GND) AND U4 pins 6, 7 & 8.

You should now be getting 5V

What does that mean?

[Input Nirvana]

Power off and disconnected, from a common GRD, or Pin 1 (U4) to Pins 6, 7, 8 or Pin 1 (USB port) is about 1.3 on the 200 scale.

[bluecar5556]

Will you be around @ 4-5pm your time?  If so, we will continue then.

[Input Nirvana]

Ya!

[bluecar5556]

4) Turn off computer, switch meter to Ω, test between U4 pins 6, 7 & 8 and USB 1 & 2 pin 1 (5V) = 0Ω

4) your reading =

[bluecar5556]

[ Attachment Invalid Or Does Not Exist ] 24589[/attach]

#1=5v
#2=5v
#3=5v


#1=?    V
#2=?    V
#3=?    V

[bluecar5556]

USB ports can be tested at the leads then optionally with a usb cable.

[Input Nirvana]

4) Turn off computer, switch meter to Ω, test between U4 pins 6, 7 & 8 and USB 1 & 2 pin 1 (5V) = 0Ω

4) your reading =

About .7 on 200 scale

[bluecar5556]

whatcha got for post #62?

[Input Nirvana]

Also, the earlier measurements that were 1.2 are now .6

Post #62 should be with power on or off?

[bluecar5556]

on

[Input Nirvana]

Just checking

At first it was  2.7 for USB ports 1 and 2 now I'm getting nothing.   On and the 2 VDC scale?

[bluecar5556]

try the (20) VDC scale

[Input Nirvana]

Nothing

[bluecar5556]

I would solder a wire from U4 pin 6/7/8 (their all bridged anyhow) to USB pin 1 (5V) but first test from pin 1 of USB AND to a known good GND.  If you do not get 5V from your test male USB cable cut in half or whatever works for you, proceed with the wire bridge.

[Input Nirvana]

I changed the 9v battery in one of the meters. I get about 1.0 on the 200 scale from any ground to U4 ground all the way to the USB Pin 1 on port 1 and 2, and at any point in between pins 6-7-8 at U4. Pins 2 and 3 have 5.15 v on U4 when grounded on pin 1 on U4. But there is no voltage out of pins 6-7-8

[bluecar5556]

Which OS is the computer running?  Some OS'es give a notification of an over current situation and automatically switches off the power to the USB ports or sometimes forces shutdown of the computer all together.  The (OC) pin on U4 stands for "Over Current" and when the temperature of U4 is past a set limit, pin 5 gets "pulled low."  

Does U4 feel abnormally warm after shutting down?


"When the output load exceeds the current-limit threshold or a short is present, the device limits the output current
to a safe level by switching into a constant-current mode, pulling the overcurrent (OCx) logic output low. When
continuous heavy overloads and short-circuits increase the power dissipation in the switch, causing the junction
temperature to rise, a thermal protection circuit shuts off the switch to prevent damage. Recovery from a thermal
shutdown is automatic once the device has cooled sufficiently. Internal circuitry ensures that the switch remains
off until valid input voltage is present. This power-distribution switch is designed to set current limit at 1.5 A
typically." -TPS2061 datasheet

[Input Nirvana]

Windows os
Holy ****! Its HOT!!  too hot to put finger on!!

[bluecar5556]

Bingo!  brb

[Input Nirvana]

Unplugged and it cooled immediately   I'm turning on again to see what happens

[Input Nirvana]

screaming hot within just a few seconds
tip of my finger is burnt.   lol

[bluecar5556]

probably the same thing, limit the current so much until the voltage dropped to 2.7V then the temp reached the set threshold and shuts down which explains your readings earlier.

[Input Nirvana]

Ok, so there are shorts between pins 6-7-8 on U4 and pins 1 on the usb ports 1 and 2. Right?

So now I need to bridge wire from 6-7-8 to pins 1 on usb ports 1 and 2 and bridge a wire from pins 4 on usb port 1 and 2 to a good ground. Right?

[bluecar5556]

Yes but you must first isolate pins (6, 7, on U4 AND usb1&2's Pin 1 from the original circuit so you may use your alternate circuit or else you will be in the same boat, does that make sense?

[Input Nirvana]

Yea. Stop the connection of 678 on U4 to the pcb and both usb pins 1.

I do or don't need to do that for the pins 4 on the usb ports?

[bluecar5556]

Now, if you don't have an ample amount of experience lifting leads or pins, I would greatly advise against it.  Lifting leads with too much pressure and the sudden release from heating the solder can and will snap them right off with a lack of finesse in the slightest.  Hmm, I'm trying to think of the easiest, safest way.

You might as well do the same for pin 4 on both usb ports just in case there is a short.

[Input Nirvana]

pins 4 on usb. got it.

I'm thinking about it too. Would it be best to desolder U4, shorten the 3 pins with a snip, then resolder?

[bluecar5556]

De-soldering U4 completely from the board?  Do you have a pair of wire cutters small enough to snip pins 6,7 8 one at a time?  They should shear evenly, say a needle held in your hand, without any twisting motion that could potentially break a lead off U4.  If you couldn't tell, breaking leads off will haunt me forever, you can never be too careful!

You can always take a shot at lifting the leads and buy another TI TPS2061 (U4) if things go south.

A questionable option that comes to mind is using a dremel with a cut-off wheel ground down to a nub on the concrete.  Then make a sturdy stand with hands on the mainboard while holding your breathe but i've never tried it.  The dremel option seems out of the question but if you have balls of steel, more power to you.

[Input Nirvana]

I can do it.

Cut 6-7-8 on U4 and both pins 1 and pins 4 on usb.

Bridge 678 and run a wire to pin 1 usb then over to other pin 1 usb. Current flows freely among those 3 points.
Wire from pin 4 usb to pin 4 usb to good ground.

I'm good.

BACK TO KEYBOARDS!!!

[bluecar5556]

You got it!  Now show em' how it's done!