Philips 30PF9946D/37 LCD

Could be ps board.

They were Philips products.

Leonard

It's a common problem with all LCD TV sets. First, try unplugging the display panel's backlight inverter board. It is very common for these to fail and cause the set to revert to standby. Otherwise, it's most likely that the PSU itself is faulty - also very common.

Examine it *very* carefully for bulged electrolytics on the secondary side. Note that these may be 'hiding' under bits of heatsink, so look carefully. Also, check all large and heatsink-mounted devices, for bad (lead-free !!) joints, which is another common cause of your described symptoms. Other than this, you're a bit 'on your own' with LCD sets. There are other possible causes, such as bad sound output chips, but if you really do have a power supply problem that's not one of the things described, then you will struggle to get to the bottom of it without schematics, and an intimate knowledge of switchmode power supplies. These LCD ones are infested with monitoring circuitry for output voltages and over-current conditions, and they all work on the standby supply, so if *any* unexpected condition is detected either at startup, or during use, the standby supply is momentarily stopped, which causes the system control micro to reset back to its 'sleep' condition, removing the 'power on' signal to the power supply. Depending on the set, that may then be an end to it until you try to bring it out of standby again, or it may just keep trying on its own, causing a flashing power light.

If you can prove which board is causing the trouble, you might want to consider just replacing that board. PSUs and inverters for many sets, can be found astonishlingly cheap on the 'net and e-bay sometimes.

Arfa

Thanks for all the great answers you guys. I was leaning towards the power supply issue. Another thing I notice is that when I initially turn the TV on, a relay clicks on (most likely on the PSU), then as the status LED goes to red, it clicks off. If I turn it on again soon enough, I can see the backlight flash for a split second.

I've had good luck repairing PSUs with noticeable parts that have gone bad (ie, electrolytic capacitors that are clearly not feeling well), so I'll check this one out, too.

I'll check the outputs of the PSU to see if they are within ranges that are standard (3.3, 5, 12, etc). Hopefully I can find my long T5 torx screwdriver since driver bits are too thick...