I only have 3.5 v on the bottom power pin that should have 24v other pins are good trying find out if I have a problem with power supply or main board
SOURCE: How to check the PSU for IP3000 printer
I've just checked mine as it suddenly stopped working - does not even light up the green button.
I'm getting 8 volts Red to Black and 23 volts Red to Yellow so I guess it's fubared?
SOURCE: 50PC5D UL I changed the
I presume because you say "All the voltages are correct" that you must have a service manual?
http://www.retrevo.com/pdf/23138ag202/9/TROUBLESHOOTING/
Above is your troubleshooting manual, below is for a service manual, if you do not have one.
http://www.service-docs.com/store/L-O%20Service%20Manuals.html
Support link below.
http://www.lg.com/us/support/product/support-product-profile.jsp?customerModelCode=50PC5D-UC&matchedModelCode=NOT_MATCHED&searchEngineModelCode=50PC5D-UC&initialTab=warranty&targetPage=support-product-profile
Right whenever a unit shuts down after a few seconds, the problem is usually an Overload, on the Power Supply or an output from a high current output.
You need to use an oscilloscope, and/or a Multimeter and monitor the main Voltage outputs, and see which one is failing, and subsequently shutting down the PSU. Usually you are looking for a short circuit, or nearly so, and usually the bad component(s) will be very hot. Often the bad part can be isolated using Freeze Spray, one freezes components one by one, and restart, the one that you freeze and clears the problem, even if only temporarily, will be the faulty component.
Now if it is NOT a faulty component, it may be that the PSU, is NOT getting the signal that indicates All is well, after the Computer does a self check, when finished it then signal to the PSU, that all is OK, and to continue to Power on, now if there is a logic fault, missing signals etc, then the PSU is instructed to power down, to stop any bigger problems occurring.
You say all the voltages are correct, well this maybe so up to a point, but obviously, they all Cannot be all OK, as it still shuts down.
You need to use the schematic diagram, and take readings around the input, output connections, and check, that indeed the Voltages & CURRENT drawn is within spec. This can be a long and arduous task.
As for your errant connections, well again the ONLY place this information would exist is in the Service Manual. You MUST check, using the manual, that signals and waveforms are exactly correct.
many many problems are actually within the PSU itself, so this is a good place to start. Then check, the load, (Sub Circuits) that connects to the PSU's individual voltage rails, looking for the problem that causes the shutdown. usually, if a short or partial short, the Voltage on that Rail, will dip, or drop, immediately before failure, I usually use my oscilloscope in Capture Mode, to check.
As related using the service manual, and schematic, work, along the Voltage rails, measuring waveforms and voltages and currents, until you find the faulty, section or component(s). Which should be replaced.
Also remember may Faults are Chain faults, meaning that, one faulty bit, may lead top another, like say, a faulty diode, is allowing AC ripple to pass and this in turn makes an Electrolytic Capacitor go faulty, so just replacing either one will NOT fix it, one needs to find and replace BOTH.
Good luck.
SOURCE: Toshiba 42RV535U again. I detected
Having the EXACT same problem. Changed out all caps near that area (About 15) Changed out all optocouplers. No change. I know it's just one little $0.40 piece causing this, but can't find exactly which one it is. Frustrating actually.
SOURCE: we have samsung LCD with
So the standby 5vdc is working but not the rest of the power supply outputs are working? Look for PS_ON signal (3.3~5vdc for ON) from the main board that feed the power supply board. You can tak ethe power supply moudule out the do bench test using 24v lamp attach to the 24vdc out put and feed the PS_ON with 3.3v to see if the 24vdc will turn on.
Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors pictures: http://s807.photobucket.com/albums/yy352/budm
Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague
Parts: www.shopjimmy.com
Parts: http://interliquidparts.com/
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx he can make you a set of caps.
Or www.digikey.com, just make sure to use caps with low ESR, 105c, high ripple current and long life rating such as PANASONIC FM or FC series.
Please post back what you find.
I have a feeling that the main board is damaged since the protection Diodes are blown, it may have taken out the processor.
SOURCE: Power supply board troubleshooting - p50x01au
If you have a service manual, please match the voltages as per that and problems might be in areas where these do not match. But read on what condition these voltages are to be checked, this is usually written in a service manual, i.e, without any signal or feeding some signal etc.
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