Substituting the supply is a good idea.  Also, the list may have 
stripped your attachments.

Tony


Carl Denk wrote:
> Here's photos.
> There is a shunt regulator there, it's a KIA431A, TO-92 case rated to 
> 100 ma. The PCB is a Lien Chang AIP0157. I should be able to make a 
> rough schematic of major components, but thought I would get this out 
> quickly. The 5 volt comes off the transformer as 1 winding. If in fact 
> this 5 volt supply is rated at 100ma, then maybe it's OK, and the issue 
> is downstream. I could try powering it from a separate 5 VDC supply by 
> itself through a 100ma fuse.
>
> Thanks for the help.
>
> Tony Vandiver wrote:
>   
>> 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
>>>   
>>>     
>>>       
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