Compaq MV740 Model: Co1056u
 

Hello, just posting a solution to a monitor problem.

Symptoms: No picture and power/standby light seems to operate nomally.

Problem: Surface mount capacitor connected to pin 8 of U702(LM2437T) on
Daughter board has shorted out.
Thus overloading the 12v line and causing the SMPS to shut
down. Now I didn't have a schematic nor
was I able to get a reading off of the original device. So I
measured one similar in size and it read about 1nf.

R715(3.3ohm carbon film) takes a beating and may have burned
the board. Replace if nessessary.

Also take a look at Q812 on the mainboard. It may have been
damaged too.

On Sat, 30 Oct 2004 23:21:40 GMT, "Jim" put
finger to keyboard and composed:

Hello, just posting a solution to a monitor problem.

Symptoms: No picture and power/standby light seems to operate nomally.

Problem: Surface mount capacitor connected to pin 8 of U702(LM2437T) on
Daughter board has shorted out.
Thus overloading the 12v line and causing the SMPS to shut
down. Now I didn't have a schematic nor
was I able to get a reading off of the original device. So I
measured one similar in size and it read about 1nf.

1nF appears too low, unless there are bigger caps elsewhere on the
same rail. See the application circuit in this datasheet:
http://cache.national.com/ds/LM/LM2437.pdf

R715(3.3ohm carbon film) takes a beating and may have burned
the board. Replace if nessessary.

Also take a look at Q812 on the mainboard. It may have been
damaged too.




- Franc Zabkar
--
Please remove one 's' from my address when replying by email.