HELP please - at a bit of a loss with this one!
TV dead apart from front LEDs - found blown fuse (4A) on PSU UB output (24V). Following replacement blew PSU primary FETs (etc.) following replacement (nice).
TV powers up and works normally if run from bench supply feeding 5V and 24V but 24V current into BL inverter is excessive - more than 6A. All 8 backlight tubes are functioning, no part of the inverter (single board Taiyo Yuden KLS-S320BCI-M) warms up and all 4 push-pull stages have similar waveforms. No transformers warm up more than the others. 'lytics have good capacitance and ESR is fine.
Reducing the contrast reduces the current but between 16/20 and 20/20 current is the same and so is the contrast (seems odd). Below 16/20 the inverter enters burst mode and modulates as expected in response to a burst PWM signal from the control board (from Atmel microcontroller). The dc current from the 24V also drops a lot down to about 2A at lowest contrast. This TV is marked 85W on the back so clearly the max. current into this inverter should be a lot less than 3A. Standby current on 24V is about 0.6A. (14W stills seems a lot).
Here's the questions - there is a second control signal out of the micro with a 10uF ceramic capacitor on it (after a potential divider) so clearly not meant to be a PWM signal - mine is stuck at a dc level which doesn't change with picture settings - should it ?
Does the micro need flashing? (how?)
Many thanks in advance.
Topic: Loewe Xelos A32 - backlight inverter excess current (Read 5477 times)