I didn't see any photos. Maybe they got stripped out along the way or you forgot to attach them? I think it is likely that the regulator is a low-current type given that 5V is probably only being used for logic circuits. If you want to try using an external 5V supply to power the circuit, the best thing to do would be to use a current limited supply with an adjustable current limit (i.e. a bench power supply). Lacking that, the fuse will work, just bear in mind that fuses are not perfect devices. A 100mA fuse will probably never blow below 150mA or so. At 200mA it may take minutes to blow. At 500mA it will blow in a second or two. At 1A it will blow in 100milliseconds, etc. Sean On Sat, Sep 5, 2009 at 5:03 PM, 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? =A0If 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. =A0I don't >> know the monitor, but 500mA at 5V sounds like a lot for lcd logic level >> stuff. =A0Then 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? =A0I 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 =A0 E74MQ363049011235 >>> =A0 =A0 Transformer =A0 LITAI =A0 PT-007921, TF-2820, 2650C0167, appear= s to be >>> an OEM custom =A0** >>> =A0 =A0 Power Mosfet =A0 =A0(2) 4511GD =A0PCB is heat discolored slight= ly in this >>> area, 8 PIN dIP >>> =A0 =A0 Voltage regulator ?? =A0AUK647, T0-220 ** >>> =A0 =A0 ?? =A0 =A0 =A0BRF1015CCT, LTGTDIP, T0-220 ** >>> LG video board =A0 75E04862 >>> =A0 =A0 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 > -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist