asus p4G533-LA / HP echo4 question

[Lex-]

Hi, this motherboard (Asus P4G533-LA) uses SMD transistors to control the VCC line (+5 volts) of some ports like USB, PS/2 keyboard/mouse, when this line is overcharged or short-circuited due a damaged hardware (keyboard, mouse, printer) connected to one of these ports then the transistor that control or switches this port become damaged, causing that the motherboard can´t "turn-on" USB and PS/2 ports (the motherboard can´t put +5v on these ports), you can verify it seeing that the leds on the keyboard stay off when you turn on the computer...

To repair these motherboards you need to know about electronics specially about SMD, because you need to locate the SMD transitor short-circuited and replace it, I know 3 ways to do this repair:

- Full repair: locate damaged transitor and repace it.

- Partial repair: if yoy can´t obtain a replacement transitor then simply remove it, but the port associated to this transitor will not work anymore.

- Partial repair (improved), you can simply remove the damaged transistor and put a jumper like a SMD cero ohm resistor between collector and emmiter pads on PCB of course, with this "jumper" the port and the motherboard will work without a problem.

Note: The Asus P4G533-LA have 3 of these SMD transistors marked as Q11 (at the back of PS/2 keyboard/mouse port), Q12 (at the back of RJ-45 LAN/ USB ports) and Q21 (near to the USB front panel header). I recommend that you first check Q12, but all 3 can cause these simptoms described by irv6744.

I hope this helps, please post some feedback to know if this procedure helps someone.

Thanks.


Hola tu computadora trae el motherboard Asus P4G533-LA, este modelo de motherboard usa transistores SMD para "accionar" los puertos USB y PS/2 (teclado y mouse), estos transistores funcionan como switches o interruptores que conectan la alimentacion o linea de voltaje de 5 volts de estos puertos, el problema que describes ocurre cuando esta linea de alimentacion se sobrecarga o entra en cortocircuito debido a que algun periferico que conectas a alguno de estos puertos causa este cortocircuito o sobrecarga provocando que el transistor que conmuta esa linea de voltaje se queme, puedes notar si este es el problema verificando que no le llega voltaje al teclado ni al mouse ni a ninguno de los USB (lo cual puedes verificar observando que los leds del teclado no encienden al momento de encender la computadora)...

Para repararla necesitas tener conocimientos y habilidades para trabajar con componentes SMD ya que la solucion es encontrar el transitor que esta en cortocircuito y reemplazarlo, hay 3 formas de "repararla" las cuales son:

- Reparacion total: consiste en conseguir el transistor y reemplazarlo.

- Reparacion parcial: consiste en quitar el transistor que esta causando el problema, esto hace que tu motherboard vuelva a funcionar pero el puerto al que va conectado el transistor dejara de funcionar.

- Reparacion parcial mejorada: en caso de no poder conseguir el transistor puedes colocar en su lugar una resistencia SMD de cero ohms (jumper o puente) entre lo que es el emisor y colector, de esta manera el puerto al que va conectado este transistor seguira funcionando sin problema.

Si vives en Mexico puedo ofrecerte el servicio de reparacion de tu motherboard.

Nota: En este modelo de motherboard (P4G533-LA) he identificado 3 de estos transistores marcados como Q11 (atras del conector de teclado y mouse), Q12 (atras del conector de red RJ-45 con 2 usb) y Q21 (a un lado del conector para los USB frontales). Te sugiero que revises primero Q12 ya que es el que yo he visto quemado en las reparaciones que he hecho pero los 3 transitores pueden causar este problema... Saludos.

[SuperCoolPCGuy]

Thanks for the excellent advice, Lex. Too often I'm faced with having to replace an entire PCB for lack of better alternatives...an electrical engineer I am not. I am but a humble PC repair tech.

Anyway I just wanted to say thanks. Your very helpful knowledge was of great help on this job and (although the USB ports that were dependent on the blown transistor are no longer operable) the machine has resumed normal POST and is running again.

[mcontoso]

I have the same problem - my son has operated with the front USB and he is very sad now. I will try to repair this. But I have no experience with smd - how to do it precisely. When I get back home I will look at the smd transistors - I should cut it out or so? Please tell me some details. In that case it is only problem with Q21 or I have to check the other 2 also. The Q21 is on the main mobo plate or on that part next the front usb sockets. Thanx, i know that is 2008 now, but we still use it (trying to).

[Platypus]

Some information about working with surface mount devices here:

http://poeth.com/smtmfg.htm

If you don't have appropriate soldering equipment and experience, the main risk is damage to tracks and solder pads on the board.

If you can identify that one of the transistors is shorted and preventing the board from booting up, eg by measurement with a meter, but don't have soldering equipment, you may be able to carefully cut the transistor leads using a brand new blade in a Stanley knife. That could achieve Lex's second repair alternative.

[mcontoso]

Thank you for your quick answer - i am reading now - not to destroy to much.
I probably use a blade, but I wonder about the glue under the smd transistor. But it can stay on its place with cuted leads, in the end.

[mcontoso]

Victory, I have fixed it 15 minutes ago.The machine is still alive. I am writing this post on it. I cutted off the Q21 transistor (next to front USB connectors on mobo) and it was that. Thanks a lott LEX, Platypus! and other people for help!

[robertmarq]

gracias Lex- tu informacion me fue muy util y pude resolver un problema con esas caracteristicas gracias x compartir tu conocimiento.

[one2go]

I had the exact same problem with my Compaq Presario S5000SX with ASUS motherboard P4G533 (Echo), S/N MXK33... and the solution above fixed it!

The wrong end of a USB camera cable was pushed into the front panel USB port, and the computer froze. Rebooting produced the initial boot splash screen (which says press F1 or F10 for BIOS Setup or Recovery), a beep, followed by a continuous beep. Pressing keys produced no change. Booting without keyboard/mouse produced same result.

Based on the solution above, sounds like the Q21 transistor shorted out, causing the motherboard to not boot. I pulled the Q21 transistor off the motherboard (using an xacto knife to cut and small needle nose pliers to pull), and was able to boot! Hooray!

The link below shows pictures of the motherboard. The Q21 transistor is just above the USB1 (Front USB) port at the bottom of the case.

http://h10025.www1.hp.com/ewfrf/wc/d...359576&lang=en