KDL40V5100

[legg]

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

[legg]

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

[legg]

On Wed, 23 Jun 2021 13:06:52 -0400, legg <le...@nospam.magma.ca> wrote:

>

Found one of 12 panels giving abnormal feedback signals
and disconnected it. Works for now.

RL