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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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More tinkering with sick LCD
I've been playing with a broken LG 566 LM LCD screen I got my hands on. I
posted about it about a week ago, and I've since replaced all of the caps on the main board with no change in the symptoms. I started poking around on the board checking voltages as best I could by following traces from the power input lines, and I noticed that there are a few caps near the two ribbon connectors that run to the actual LCD panel that have voltages written next to them in the silkscreen. The voltages written are 9.2, 3.3, 18, and -6 volts. The caps themselves are rated well above these values. Measuring between the positive side of these caps and ground with the unit powered on, I get nothing above 4.5 volts -- does that seem odd, or is there something about the way I'm measuring that would give me false readings? I do have good voltages at the input from the power supply, 2x5v and a single 12v, but since the one visibly bad cap that I replaced in the power supply was on the 12v line, I'm wondering if there is some component on the 12v line of the main board that shorted or went open and is causing problems. If anyone knew where I might be able to find a schematic for this unit that might help me out, I'm by no means a professional tech but I like to learn what I can by tinkering with broken gear... especially when there's nothing to lose, as in this case! All I have is a DMM and some spare time once in a while, but I'm hoping I might get lucky and find one bad part that is the culprit. Thanks in advance for any help! |
#2
Posted to sci.electronics.repair
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More tinkering with sick LCD
Just wanted to follow up on my post about the LG 566LM lcd screen I asked
about a few weeks ago. Long story short, it suddenly started working on me one day after a few hour long visits to the freezer, but would gradually degrade as it was left powered up. I bought some freeze spray and was able to narrow the location of the temperature sensitive part to one region of the board. By freezing the end of a Q-tip and probing in that area, found a single SMD cap that, when frozen, brought back a nice clean picture. The cap was between pin 5 on an AIC1341 chip and ground, so I removed it and installed a regular old cap of the same value directly between that pin and a nearby ground. Works great now! |
#3
Posted to sci.electronics.repair
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More tinkering with sick LCD
Cool fault searching trick (excuse the pun).
Must remember that. Bart Bervoets "JM" wrote in message ... Just wanted to follow up on my post about the LG 566LM lcd screen I asked about a few weeks ago. Long story short, it suddenly started working on me one day after a few hour long visits to the freezer, but would gradually degrade as it was left powered up. I bought some freeze spray and was able to narrow the location of the temperature sensitive part to one region of the board. By freezing the end of a Q-tip and probing in that area, found a single SMD cap that, when frozen, brought back a nice clean picture. The cap was between pin 5 on an AIC1341 chip and ground, so I removed it and installed a regular old cap of the same value directly between that pin and a nearby ground. Works great now! |
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