A Sony KDL40V5100 gives lamp error indictions (6 blinks) but the inverter seems to run normally, if burst duration is used for brightness control. Burst periods ~ 4ms which would be acceptible for this kind of backlight. Amplitudes seem well regulated.
Service manual pretty uselss without schematics and typical waveforms/voltages. No hints about fault signal tracing.
Early start-up messages are normal - just won't enter into a useful standby mode.
Any ideas?
RL
With a schematic for the power board only, I find a balance error, inverter error output lines and a backplane control input line.
Balance error signals originate in the inverter balance assy where the flourescent backlight elements pick off their drive. A glitch every time the inverter turns on being normal - but this unit develops continually noisy balance error signals after about 4 seconds, which activates an npn/pnp latch to crowbar the 'backlight on' signal input line.
If the latch is disarmed, the external processor shuts the board down anyways based on balance error output signal. If this output signal is overidden, the backlight still turns off after about 8 seconds - Don't know why. Possibly due to 'missing' balance error glitches from normal dimming action, if the programmer was being a real jerk.
The balance board is mostly magnetics - 12 small ccfl inverter transformers being fed from the same main inverter on the power board. Inverter seems to run with no issues - lamps light ditto. Not sure how balance issues are being created - can't see any coupling caps to fail. Will have to check each load for current, somehow.
There should be a 'run till you catch fire' jumper on this thing.
RL
Found one of 12 panels giving abnormal feedback signals and disconnected it. Works for now.
RL
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