RCA RT2620 My RT2620 will not power up. The standby light switches from red to green, but I get no display and no activity. Unplugging the unit for any extended period does nothing. I'm ready to start replacing subassemblys', but i don't know which one to buy.

Sounds like either a blown mainpower fuse or the thermal fuse for the power transformer. If the protect circuit was kicking in, the display would light up, but then turn off with a red blinking light. the green light with no display means the transformer is not getting power.

How many times this standby/power light blinks at one time switch ON? Count it carefully. These blinks are fault indication, and known as blinking codes. From the number of blinks occur at one time switch ON; you can get an idea about the faulty circuit stage inside the TV. This will make repair easy. For more information, check the link http://electronicshelponline.blogspot.com/

green green is power on, normal
then it tries to light the lamp, but it can't so the protection circuit comes activated.
you get red and green blinking

Then it goes to standby, red and off.

so something has happened to the lamp, or lamp ballast power supply.
Take the lamp out and check if all is OK with the 2 terminals in the connector, and the leads to the lamp are intact.

Failing that, I would suspect the ballast lamp power unit

Is the red light flashing at first?
The unit may be going into protect mode. Lets hope it has done the job and the receiver has protected itself from failure.
Protect mode can result from speaker wires touching each other or the Amps metal case. Check that first.
It can also be caused by unstable ohm loads if too many speakers are connected to any of the outputs especially zone 2.
If you can remove all speaker wires and turn the unit back on. If it stays on, turn the volume down on the main zone and zone 2 if connected. Then reconnect speaker wires.

Here's an excerpt from the Sony Manual online. And the link - http://esupport.sony.com/US/perl/webtree.pl?template=EN&mdl=KDF55XS955&content_id=68&category_id=11&problem_id=52

The POWER/STANDBY (red) indicator flashes three times
If your power/standby indicator is flashing in a pattern of three flashes, this may indicates that the lamp cover is not attached securely. Follow the directions in the Operating Manual under changing your lamp that related to closing and securing the Lamp Cover. Ensure that the Lamp Cover Door is securely fastened by tightening each screw.

The POWER/STANDBY (red) indicator flashes continously
If your power/standby indicator is flashing continuously, and the lamp cover has been secured, your TV may be in need of service.

The POWER/STANDBY indicator is lit up green (not flashing)
A sustained green light indicates your TV is on.

The POWER/STANDBY indicator is lit up red (not flashing)
A sustained red light from your power/standby indicator simply indicates that your TV is in standby mode. This shows you that your TV is ready to be turned on with the remote.

Is it the power light and not the lamp light? If the lamp light is flashing then replace the lamp.

The only solution at this point would be to get the power supply repair since new boards are not longer being manufactured. In about 95% of the time if the LCD doesn't power up or turns OFF by itself or need to be unplug for some time to make work again; those are the symptoms of a dying or defective power supply.
I service these power supplies, for more info write to [email protected]

I have had this same problem twice in the past 3 months. So far both times I've been able to get it back after a week or two. I'm not sure what works, but unplugging and detaching the antenna and cable and waiting a few days seems to be the key. In both instances, I unplugged it for a few days then plugged it in for a few days and repeated the processes until I eventually got the steady red led. Both times prior to the red led the led would flash red then green and make a clickiing noise for several hours before I was able to get it working again.

if you have p scan you need red green blue cables to the tv and both need to be set up to do p scan, it sounds like you have p scan but its not cabled correctly.

I have this exact problem, it appears the power on/off switch no longer works. After re-setting by unplugging the unit, use the remote only. As for the display, I find that if I turn the home theatre on last, the unit works and if I turn it on first, it behaves as you described.