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jiipee
Joined: 16 Nov 2013 Posts: 2
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Posted: Sat Nov 16, 2013 9:16 am Post subject: Samsung LE40F86BD repairs |
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I am repairing this TV which has horisontal lines on screen and some color flicker. I think I have found the problem to be unstable voltage on T-CON board. Voltage at testpoint marked VONB has ripple of 5-7 volts maximum value being about 20V. This voltage is taken to the panel. T-CON board has similar test points usually marked as V**** and all of them have stable DC voltages present.
1. Service manual for this TV found at this site seems to be corrupted (unexpected end of archive...). Does anyone have schematics of the T-CON board BN81-01281A?
2. Can anyone confirm that my finding is corrent? Should the voltage at VONB be a stable DC voltage?
3. I believe VONB is just the 20.6V voltage generated by the switching power supply but which is switchable on/off with FET or BJT. The switching PSU output voltage is OK. |
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jiipee
Joined: 16 Nov 2013 Posts: 2
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Posted: Sat Nov 16, 2013 10:03 am Post subject: |
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Update:
1. The voltage I thought was having ripple seems to be OK. I found similar testpoint marked VONF from the other corner of the board and it is very similar (almost square pulses). So I don't think that was the problem.
2. After disconnecting and reconnecting T-CON board for measurements the TV image is suddenly perfect. So, this seems to be connection problem after all. I have been re-seating, tapping and cold-spraying the connectors already but this is the first time the image is fine.
3. I have to clean the connectors as good as I can now... |
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