Re: Lg 60PK550 Problem
Hi everyone
Had to come back from a long hiatus needing help with 60pk550 TV. Had a quick check no obvious diode shorted, all caps appear ok, checked the 3 ceramic resistors...measured 10 ohm @. double Clicking coming from one of the relays has a period of 1 to 2 sec. Disconnected main board / video processor board from the PS the relays only click once. Has anyone got a circuit for this TV?
jumba
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Last Activity: 07-04-2021, 12:49 AM
Joined: 05-08-2006
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Last edited by jumba; 12-15-2016, 06:46 PM. -
LG Flatron L1710M flourecent backlite tearing
Need help to repair this unit. This unit backlite is tearing in brightness only. Backlite inverters show some heat distress as the pcb is going slightly yellowish.
Thanx in Advance -
Re: Dell E172fpb
Thanx kmkbeni for ure dead board. Can confirm it has the same fault as mine did. Replacing both transistor pairs Q159,Q160 & Q139,Q140 before working out transformer parametersLeave a comment:
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Re: Dell E172fpb
If it is one pair always failing then it's likely a shorted turn. This causes the transitors drawing higher than normal current. If one measures the current consumption in both ccts; the faulty cct will be higher. Solution find a replacement tranny or rewind it.Leave a comment:
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Re: Dell E172fpb
Thanx for the cct it confirms what I had traced 12 months ago. The higher beta transistors are the way to go. 3055 transistors are lower and may have not enough gain to startup. If the transistors are cooking the problem is shorted turn or a faulty cap in the o/p cct. My unit is still going strong since the repair but when it's not in use turn off the power! If the unit goes faulty in standby with shorted transistors the transformer cooks. The clue is the yellowish discolouring around the fluro cct.
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Re: Dell E172fpb
There is no road map for the dell on the web.Leave a comment:
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Re: Dell E172fpb
Hi,
With my Dell, the green light flashing was in unison the back light flashing. The monitor image could be momentarily seen. Does your's do that? Why not remove the faulty tranistors and run the monitor on one back light to see if the unit is basically functioning. My experience with throw away items is, parts are no longer available after manufacturing has ceased. So, short of rebuilding the transformer the chances of getting a replacement is slim, in particular, as these units come from China!Leave a comment:
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Re: Dell E172fpb
Since replacing the second set of transitors with 2SD1804 and turning off the power to the screen when in standby, I had no problems. After sketching out the circuit it appears that there are 2 transformers for each side that are identical only one that's driven by the tranistors. For some reason the tranistors blow and then cook the transformers whilst in standby.As I had caught the second pair faily early the board was not discoloured when compared to to the other cct that had been left on for days in standby mode . So if you can get your hands on another dead...Leave a comment:
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Re: Dell E172fpb
Just fixed the Dell again, this time one the original transistors failed; a dead short between all pins. Noticed that even with pulsating the circuit gets hot quickly. If one leaves the monitor on this could over a period of time cook the pcb and even a tranny. So as a precaution turn off the power to the monitor when not in use, this this should reduce the secondary damage from occurring. After sketching out a circuit there are two caps with a value of 0.15j x 100v they are connected to the collectors push pull inverter cct. This causes the switching waveform from...Leave a comment:
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Re: Dell E172fpb
Repaired display a few weeks a go transistors blew again but noticed that back light was nolonger pure white before tranistors turned up thier toes! I plan to draw cct to figure out the problem. The clue is that the pcb is discloured suggesting the cct is running Too Hot! Two possibilities come to mind either the series cap to the backlight is faulty or the tranny has a shorted turn. This will cause the transistors to run hotter and in the end fail again!Leave a comment:
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Re: Dell E172fpb
Got the tranistors yesterday put them and hey presto the unit works again. Time will tell if it is just the tranistors. Purchased 2SD1804 as alternatives from B&D Enterprises.
Min Order $15 which translated to a qty of 32; however shipping more than doubled this figure using UPS global Express (air mail) for a very light itemLeave a comment:
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Re: Dell E172fpb
Hi All
It is very strange that all faults are the same. Has anyone found the first tube tranistors gone?
I 've looked at the trannies with a multimeter. The one closest back light plug is shorted every which way about 0.01 ohm. The other one is not as drastically damaged but still stuffed. The base emitter resistance is approx 70 ohm with the base to collector still showing a diode characteristic. This type of failure happens when the base is overdriven fusing the base to emitter. The transistor that is shorted between all pins is probably...Last edited by jumba; 05-09-2006, 08:28 AM.Leave a comment:
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Re: Dell E172fpb
Many, thanx for the solution, the trannies are shot.
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