Are you sure that the 5V supply is a switching supply and not a linear 
regulator TO-220 using the 12V as a source?  If it is a linear 
regulator, 1/2A gives you 3.5W in the regulator which is over the limit 
for TO-220 packages unless it's got an incredible heat sink.  I don't 
know the monitor, but 500mA at 5V sounds like a lot for lcd logic level 
stuff.  Then again, I know someone who makes a living replacing LG 
supplies in televisions so I'd lean toward the supply being bad too.  
Can you post a few pics of the power supply?  I couldn't really follow 
the parts description.

Tony


Carl Denk wrote:
> Disconnected cable from power supply board to video board, and the 5 
> volt supply measured at 5 volts. Used a 20 ohm resistor to create a 1/4 
> amp load, still had 5 volts, changed to 10 ohm resistor for 1/2 amp 
> load, and the 5 volt was back to a couple of tenths volts. I'm assuming 
> that some regulator chip is shutting down due to over current, but am at 
> a loss where to go from here.
>
> Some of the components are:
> LG monitor model LT953LS
> LG power supply board   E74MQ363049011235
>     Transformer   LITAI   PT-007921, TF-2820, 2650C0167, appears to be 
> an OEM custom  **
>     Power Mosfet    (2) 4511GD  PCB is heat discolored slightly in this 
> area, 8 PIN dIP
>     Voltage regulator ??  AUK647, T0-220 **
>     ??      BRF1015CCT, LTGTDIP, T0-220 **
> LG video board   75E04862
>     1.8 volt regulator for video chip, AZ1086S-1.8EI
>   
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist