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Russell H.
Russell H., Service Tech
Category: TV
Satisfied Customers: 9514
Experience:  8+ years of professional experience
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Sanyo DP50749 wont power on. light secs and then shuts off.

Customer Question

Sanyo DP50749 wont power on. Green light for 5 secs and then shuts off. Replaced main, power and logic boards, all with same result. Disconnected y-sus and z-sus, same results.
Any more ideas?
Submitted: 4 months ago.
Category: TV
Expert:  Russell H. replied 4 months ago.

Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.

Something in the TV is shorted out, I suspect. There are various approaches that can be taken to this... but tell me, do you have a meter, and a service manual for this TV's model line ?

Customer: replied 4 months ago.
I have a meter and a service manual along with schematic. I cannot upload it here because it is 7.1 mb. I can upload to a dropbox or email you if u like?
Expert:  Russell H. replied 4 months ago.

I don't need the service manual myself.

What have you gotten in the way of indications from its diagnosing or troubleshooting procedures/tables... if any ?

Customer: replied 4 months ago.
Thats where my skill level stops. I havent been able to go any further. Ive already replaced the power, logic and main boards. No change. I unplugged, both individually and together, the z-sus and y-sus boards and there was no change. I checked voltage at the power supply for the z-sus and y-sus it came to 60 and 190, if I remember correctly.
That being said, it seems the correct voltages are there at the PS side. Now, I disconnected one-by-one the sustain boards, in order to eliminate them. No change.
What do you think?
Expert:  Russell H. replied 4 months ago.

The power supply may be defective or damaged. In short-circuited-component cases, the power supply may still be damaged even when the shorted board at most fault is replaced. So very often either two, or three even, of the boards must be replaced.

However, if the 'shorted and not staying On' behavior continues, the shorted component is either not replaced, or still connected to the power supply and draining power from it to excess.

And no, I shouldn't pretend that these sort of cases are easy. They aren't. But they can be gotten through, with an intelligent-enough approach.

One very crude approach to diagnosis is to unplug everything from the power supply, pretty much, and see if it stays On, then connect one board up, wait a bit to see how that affects things, then another board, and so forth until one board, connected up, causes the TV to shut Off. I don't recommend this... but if other approaches have failed, it may provide an indication.

Have you examined all boards on the TV quite thoroughly, component-by-component? visual inspection cannot find everything of course, but a burnt-out component will have a brown spot on the other side of the circuit board, or will look melted/heated a bit; also, capacitors that are leaking, or the top is bulging, need replacing beyond question.

Customer: replied 4 months ago.
Bad caps are one of the first things I looked at. I can attempt to disconnect everything from PS and proceed from there. The only thing I have not replaced are the sustain and buffer boards.
Customer: replied 4 months ago.
I have replaced the PS with no change.
Expert:  Russell H. replied 4 months ago.

I understand. Proceed with care.