Since retirement from an industrial electronics, technical field, and after a lifetime in the electronics field, But with a wish to still keep my electronics skills "alive" (or mebe it is the brain) I began to repair monitors and computers saved from a fate worse than death (LandFill).
I donate repaired PC's and monitors to local church groups for them to give to "New Australians".
The majority of monitors (and some motherboards) mostly suffer from the same faults, they can and often do fail earlier than three or more years old.
The frequent cause of failure is overheating and secondly frequent power voltage surges from the mains supply.
With Mains Power OFF, CAREFULLY ----Vacuum and Soft Brush clean the CPU HEATSINK and FAN, vac and brush all air intake and exaust grills, and bottom air intakes of front panel of PC and air grills of monitors and TV's.
NOTE WELL, entertainment equipment and computer - Power Supplies take the brunt of the mains voltage surges especially during storms, (get good surge protected mains power distribution boards, Cheaper than having to buy a new computer DVD, Video Blueray etc, ) DO NOT USE multiple piggy backed double adapters, if its valued, disconnect power from wall during storms.
FAULT INDICATORS
Monitors can flash on briefly then off (power switch off then on repeats fault), Dead screen but with power on, led indicators can be still normal on green etc, Power led can can flash on off repeating.
Motherboard faults can be legend, dead with fans on, simply dead, restarts frequently, constant errors due to poor voltage regulation of critical circuits.
see attached files for everything below.
Look For Faulty LOW ESR Electrolytic filter capacitors, Tops Bulged and sometimes rubber bottom plugs blown out, (Overheated and Leaking a drop of orange goo) 220Mf, 470Mf, 1000Mf and up to 3300Mf (MicroFarad) and usually rated at typically 6.3Volt DC to 25Volt DC. note the LOW ESR component of these capacitors can not be tested reliably with a multimeter, replacement with non LOW ESR capacitors will fail again usually within the year sooner in high temperature climates and working computer cases.
Usually if there are Bulged LOW ESR Capacitors on the Motherboard or video card then the Power Supply is highly Suspect as well, (much swearing heard #$%$#@#^%^$##$%$#$).
REPAIR NOTES
Look for and check the mains input fuse for continuity (zero ohms across) and the 3-4 amp feeder fuse (zero ohms) supplying the current to the inverter circuit.
Blown surface mount W or O marked 2-4AMP fuses, and look for the fuses (often look like black unmarked resistors) of the same values which feed the voltage inverter circuits of most television and monitors.
Look for arcing and burnt markings around all parts with the power off.
Sometimes there will be 1 or 2 failed, Field effect transistors feeding the 2-4 PNP or NPN transistor drivers for the 2 to 4 high voltage output transformers, (high voltage conversion of square wave input)--Which in turn drive the cold cathode fluorescent lamps (backlights)
After replacement of any suspect capacitors and fuses, it would be prudent to remove (desolder from the board) and check the inverter cct Field Effect transistors with a multimeter preferably against a new good replacement pin to pin, or at least test- gate to drain, gate to source, reverse leads and recheck, then drain to source- reverse leads and recheck, If using a multi meter look for gate to drain and gate to source pins appearing open circuit to 200Kohms all directions, and the drain to source pins 600 to 750 ohms typical and more than 200Kohm leads reversed.
Typical is the FQU11P06, J598, IRFU9024N FU9024N, STD10PF06 D10PF- FETS used in a variety of BENQ, Dell, Chemei and ACER monitors - inverter/power boards.
The high voltage transformers can also produce shorted turns (feel for heat on top) and over time, cause the transistors supplying current to them to blow, The CCFL's can also age badly and draw more than usual current, feel for heat on top of the transformers and dull low light from screen if still working.
Removal of the transistors and testing with multimeter ohms range (Diode or 2kohms) base / emitter, base / collector=(low ohms, reverse leads, high ohms), emitter / collector (high ohms, reverse leads, also high ohms) these readings usually denote transistor is good and with a little luck the transformers quantity 2-4 on board good as well,
Replacement of the components is usually cheap on EBAY in quantity of 10x. got to love GOOGLE!!
With luck another unit will be saved for use again
I have included a pdf file from Jestine Yong which gives a good description of some of the problems, a wikipedia web page artical on faulty capacitors and an ebay reseller web page useful to source all of the different types of parts including the kits for each model of monitor.
All other (typing) faults are mine
Bill Materna
