DELL 2405FPw LCD Monitor Dissassembly
http://youtu.be/SZE_R8CPtM0
(Samme mekaniske opbygning som 2407)
Dell 2407WFP Monitor Power Button Repair Part 1
http://youtu.be/RXAQxwCTuuI
Dell 2407WFP Monitor Power Button Repair Part 2
http://youtu.be/zH3y3FAP-LY
Dell 2407WFP Monitor Power Button Repair Part 3
http://youtu.be/WaCf3O_XX7Y
Dell 2407WFP Monitor Power Button Repair Part 4
http://youtu.be/WsFQjlCmp1w
Som uddanet radiomekaniker og elektroingeniør, så tvivler jeg dog på at det er støv der er årsag til at monitoren fejler periodisk. Det er typisk en dårlig lodning eller f.eks. en lækket elektrolytkondensator der kan fremprovokere periodiske fejl, når apparatet varmes op.
Dell 2405/2407 er tilsyneladende et af de utallige forbrugerelektroinkprodukter der er ramt at skandalen der længe har verseret med elendige billige taiwanske kopikondensatorer fordi producenter i deres iver for at spare nogle ører droppede japanske kvalitets elektrolytter:
http://www.badcaps.net/forum/showthread ... b0&t=14882
Så det kan meget vel være en eller flere dårlige elektrolytter der har lækket eller buler ved sikkerhedsventilen i toppen.
Generelt bør man holde sig til europæiske eller de mange japanske eletrolytfabrikanter, for at få kavlitetslytter. Der er alt for mange elendige kopier fra andre asiatiske lande som Taiwan og Kina.
Men man skal ikke bare selv give sig i krig med at købe erstatningslytter uden virkelig at vide hvad man har med at gøre. Det er langt fra nok at købe en lyt med samme påtrykte kapacitet, spænding og temperatur. Andre specs som man ikke kan læse på huset, så som ESR og max ripplestrøm er mindst lige så vigtige, især til switched-mode strømforsyninger.
Jeg har tidligere arbejdet hos Bang & Olufsen og mener aldrig jeg har set andet end europæiske og japanske lytter. Aller komponentfabrikater skal testes og godkendes før de må anvendes i produktionen og tror ikke de havde godkendt nogen elektrolytter fra andre asisatiske lande end Japan. B&O går mere op i kvaliteten end at spare nogle håndører på billigere elektronikkomponenter.
Desværre har de langt de fleste elektronikgiganter i computer- og forbrugerelektronikbranchen og ikke haft den samme holdning og rigtig mange har købt de billige fejlbehæftede taiwanske lytter i håb om at kunne spare lidt på hvert produceret apparat, men med ringere pålidelighed til følge og der er ikke kun tale om discount og no-name producenter, men også højt respekterede mærkevare producenter. Desværre har det nu vist vist sig at give bagslag for rigtig mange producenter. Men desværre for forbrugerne er de fleste apparater først begyndt at fejle efter garantien er udløbet.
Jeg har selv lige repareret en Asus router med 6-7 defekte taiwanesiske lytter. Det viste sig at der var defkte bulede lytter i både netadapteren og selve routeren.
Beskrivelse af problemet:
http://www.badcaps.net/forum/showthread.php?t=425
1. [ Introduction to the Problem ]
1.1. What is the story behind the BadCaps phenomenon?
Well, the rather dubious story behind this problem is that a scientist working for the Japanese company Rubycon left the company and began working for Luminous Town Electric in China. He developed a copy of the Rubycon P-50 water based electrolyte which is what they use in the Low-ESR caps that are present on all motherboards. Unfortunately his staff left and stole his electrolyte formula. They started producing tons of the electrolyte and supplied many Taiwanese capacitor manufacturers. Unfortunately the formula was incomplete and did not contain the additives that prevent electrolysis from occurring inside the capacitors and releasing hydrogen gas which bursts the capacitor at the vents at the top or at the bottom of the capacitor can.
Check also the following link :
Topcat's - What Causes Bad Caps?
http://www.badcaps.net/causes/
http://www.badcaps.net/causes/
What Causes This Disaster?
How did this happen?
The reason this problem exists is because of a large-scale industrial espionage foul-up. Some companies decided to steal an electrolyte formula from another competitor. Little be known to them, the stolen formula was incomplete and flawed. They didn't discover this until it was too late and they had manufactured and distributed literally MILLIONS of these flawed capacitors. It was way too late for any kind of recall, and even today, these crappy components are being used in new boards. As I mentioned before, I believe this problem runs much deeper than simply an industrial espionage screw-up, as that incident was exposed years ago, and the problem still exists today. Nowadays, it just boils down to corporate bean counters cutting corners to save money by using shoddy components.
The cause...
This inferior and flawed electrolyte formula was used by a number of component manufacturers that sold to many different, reputable, and well known motherboard manufacturers. This problem isn't isolated to one particular brand of motherboard, and not even isolated to motherboards alone. I won't mention brands, but a VERY popular monitor manufacturer has been plagued with RMA's on some of their monitors that were built using these inferior capacitors. This problem has been reported in computer motherboards, monitors, televisions, radios, and stereo equipment. Through my experiences owning a service center, I've personally seen and serviced a large number of 'high-end' equipment that had prematurely failed capacitors.
More detailed information...
In more technical terms, this is is what actually happens to the capacitor...in the simplest of terms. Think of an electrolytic capacitors as a battery. They are designed to store a charge and release that charge depending on the specific requirements of the circuit. Inside the capacitor there are two metal plates with dielectric material between them, wrapped in paper, filled with acid (electrolyte), and sealed in its housing or 'canister'. What happens is the flawed electrolyte prematurely deteriorates and dries up. When this happens the capacitance value changes, becomes erratic, and can even short completely, which obviously causes the circuit to malfunction. On your motherboard, this results in system instabilities or complete failure of your board.
From a physical standpoint, the capacitor can display a number of symptoms and even have catastrophic failures. Catastrophic failure is a rare phenomenon, but it does happen. The reason is this... A capacitor canister is completely sealed and air tight. When the electrolyte dries it turns from a liquid state into a gas. This gas expands with heat and builds great pressure inside the canister, the theory is the same as a pressure cooker. Of course the obvious happens when that pressure builds too much, and the capacitor will vent. This is what causes the capacitor to 'bulge' or swell up. In a catastrophic failure, the capacitor may actually burst or explode. It can sound like a firecracker going off or sound similar to air escaping from a car tire, depending on how high the pressure has built. A physically failing capacitor has an ammonia-like odor (at least that what I thought it smelled like)... Capacitors that has swollen up are easy to detect, but one that has burst are even more noticeable. It will usually blow from the top and spew its innards throughout your computer case. The innards are mostly paper and any remaining electrolyte, but it sure can leave a mess... Once again, catastrophic failure is a rare phenomenon... It's not dangerous either, as long as you practice common sense safety precautions! If you suspect bad caps, don't put your face near them while the system is powered up, and don't eat the paper or electrolyte that they blow out!
