I have a WS-55807 that will not power up. When the power button is pressed I hear a click from the back of the set, the timer light comes on and 3 seconds later I hear a click from the back of the set, and the timer light goes off. I started checking power to the unit with a voltmeter. For those intersted I have attached scematics: I verified that the PCB main fuse is good and there is 120V at point PT.
From what I can tell is happening, the power button is pressed and the P-ON transistor is given a signal to conduct which causes K9A50 to close. K9A50 opens after about 3 seconds.

I am looking for other troubleshootinng steps. I have checked fuses F9A01 and F9A06, both are good. What are some other things to check for? Where does the P-ON signal come from?

In the switched supplies regulator circuitry I found fuses F9A04 and F9A05 blown (denoted by red lines thru components). I jumpered around F9A04 and F9A05 with good 5A fuses and the TV powered on. However when the set was plugged into an outlet there was a huge power draw (sparks from the outlet).

After jumpering around the blown fuses, the TV stayed powered on for about 30 sec and then powered down. I pressed the power button a few more times and the same result. The TV stayed on for only 30 sec.

I pulled the middle PCB whichs holds these circuits and I found the
D9A60 diode open and IC8C02, one of the convergence IC's fried. I don't know if these were like this before or after jumpering.

I replaced all bad components and I am back to square one. The K9A50 relay stays closed for 3 sec and the set does not power on any further.
Comment by TV_ITGuy, posted on Dec 19, 2007 Thanks for the advice ctf1800. I have read several posts that speak of the DM unit. I have looked in the back of my set and the DM unit is not in the location shown in the pictures.
As I hope you can see in this picture, there is no DM unit to the far left, just open space. Also the service manual for the V17 chasiss does not speak of a DM module.

I checked the reisitors on the output of IC8C02 which are a couple of 3.9 ohm resistors in parallel. When I test them I get approximately 1.9 ohms, which is what it should be with them being in parallel.

Please let me know if I am off base on any of this. Thanks Comment by TV_ITGuy, posted on Dec 19, 2007 Also, I have replaced both of the Convergence IC's when I replaced the fuses and diode. Post Solution Work Queue --> Have the same problem? --> Have the same problem? Click Here
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ctf1800
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first off you should replace both convergance IC and check the resisters coming off the output if any of the resisters are bad it will trash the ic on trying to power up.
i would also replace the caps in the DM section
http://www.jeremyburns.com/Mitsubishi-Green-Blinking-Light-Fix.pdf

http://chrisandnat.com/projects/blinkingtv/blink.htm

Comment by ctf1800, posted on Dec 20, 2007 there are six fusible return resistors ranging from 1.5, 1.8, 2.2, 2.7, 3.3, 3.9 Ohms. I would lift one side of the resister out.
check for any caps that look puffy and check the horz. out put transistor.
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Hope this helps fortuna55@aol.com