The defect showed as follows:
When plugged in, the blue power LED came on immediately and none of the other buttons reacted to touching. The device was totally unresponsive.
In this thread on Badcaps I learned that reflowing the main board revived some of the sets. Before that I did my voltage check routine and found nothing suspicious. The 23.5V were there and all the secondary voltages looked good as well.
The right chip under the heat sink was warm, the left was stone cold and its clock wasn't oscillating. It seemed as if the right main BGA chip would activate the left after booting.
So, my brand new reflow controller got something to prove its value. It is a clever device, which controls a normal el cheapo pizza oven precisely via a feedback sensor, which I taped directly on the BGA chip.
Before I ran the standard profile, I poured some liquid flux under the chip. I don't know if this had a part in the success, but I thought it wouldn't hurt.
And voilà! The monitor ran flawlessly again. Hallo Frau Johansson!
During my research I came across an interesting software, which is able to reset the factory defaults in a monitor. It's called softMCCS and is available here: http://www.entechtaiwan.com/lib/softmccs.shtm
It identified my two monitors. First, the defect 2709 would be found, but DDC/CI was marked as "not supported". After the repair, it read "supported". So this is a nice tool to check whether the processor is working ok or something else is broken.
Rest in Peace
14 months later the error came back. A second reflow did not fix it. I also learned that the larger electrolytic capacitors did not like the oven heat. They were bloated afterwards. I'll remember that for my next reflow task.
Hi,
ReplyDeletehabe den gleichen Monitor und Fehler , wie bekomme ich den Kühlkörper ab ?
Gruß Peter
Ja, da musste ich auch eine Zeit meditieren. Ich habe ihn erst erhitzt und dann mit vorsichtigem Hin- und Herdrehen abgelöst. Auf keinen Fall weghebeln versuchen!
ReplyDeleteDie Stifte muss man einfach auslöten.
hi,
ReplyDeletedanke für deine rasche Antwort,werde es mal probieren
hast du evtl auch eine Bezugsadresse für ccfl-röhren , passend zu diesem Monitor ?
und eine Anleitung um diese zu wechseln , da eine gebrochen ist :(
Gruß Peter
Tut mir leid, damit kann ich nicht dienen. Mit CCFLs habe ich (zum Glück) nie zu tun gehabt.
DeleteYou did not mention the temps. you reflowed at. I assume it was above melting point of the solder. I have seen numerous posts where boards have been brought back to life by heating, (though I suspect only temporary) with hairdryers, in the oven at 275F etc. Well below the melting point of solder. I don't doubt their successes. My question is why does it work if the temps are not hot enough to melt and reflow. My theory is that flux is key to their successes. I think when connections break they start oxidizing and eventually are nonconductive. The flux and heat remove the oxides and contact is made again for awhile. What is your confidence in a reflow repair?
ReplyDeleteThe Reflow Controller is microprocessor-controlled and runs a temperature profile. I don't interfere manually at all. It goes up to 230°C for a few seconds. I always let some special liquid flux flow under the chip before the process.
ReplyDeleteMy confidence is high if the cause is really broken balls. Sometimes reflowing is just the last chance taken before dumping a board.
Thank you a lot for the article. Could you please give me one more hint to removing of the heatsink? You wrote that you heated it up and released it by carefully applying torsional force to it. Then you wrote that the pins have to get simply de-soldered.
ReplyDeleteI am sort of missing the simplicity of that. The pins seem to be press-fit to the heatsink. It seems to me that both parts have to be done in one step. Did you heat the heatsink from the top to melt the solder holding the pins?
OK, never mind, it's done. I just heated the heatsink pins (one at a time) from the back side of the board using a soldering iron while prying on the heatsink with my fingers. The thermal grease gave up in the process and detached from the chip.
DeleteI used a desoldering pump to free the pins from solder, and a strong iron.
Delete