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Louie, Technician
Category: TV
Satisfied Customers: 2557
Experience:  25+ yrs. experience in the field and 5+ yrs. online, down to component level.
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Rick I have a Hitachi 55" plasma. Model 55HDT79. It has sound

Customer Question

Hi Rick I have a Hitachi 55" plasma. Model 55HDT79. It has sound but no picture. This started slowly, over a period of a year or two. The TV has no trouble codes from both front led (blue light) and night ranger codes.
Ok, I have checked all obvious issues ie. Caps, burnt circuits ect. The power supply gives stand by power but no high voltage.
I wanted to see if I could get the power supply to fire off but I'm not sure which pins I would use to ID that. By this I mean making sure That the power supply will in fact power up. What do you think?
Submitted: 2 years ago.
Category: TV
Customer: replied 2 years ago.
Lost connection are you there?
Expert:  Anthony_Infotech replied 2 years ago.
Hello my name is Anthony
Thanks for the Question
This set does not generate error codes
I am not sure what you mean by "this started slowly over a year or two" do you mean the screen has been going black but coming back on again?
Is the blue light in the front on solid?
Customer: replied 2 years ago.
First, thanks for getting back to me so soon. This particular TV dose have a self check system called " knight Rider" as they call it. It is a series of five LEDs located on the main board that run a self check sequence at start-up. What it checks is digital tuner, analogue turner, MPEG, memory, ect. It can only be viewed with back cover removed.
It dose preform as required. ( system ok). That's good news anyway!
On the symptoms question. It started approximately two years ago, I would go to turn on the Tv, no picture but sound. I would turn it off wait a minute or two. Turn it back on and it would be ok. As time went by, this became more freaquent. And finally, no more picture. But always sound.
The blue light performs as correctly, Red standby, Ok, Blue on, Ok, Orange on no signal, Ok
Expert:  Anthony_Infotech replied 2 years ago.
So your a technician then?
So I assume the display is going black, what about the scan boards are they getting warm on the heatsinks? I am inclined to believe the set is stopping the scan namely the Y scan and the buffers on these sets are particularly prone to failure
Let me know
Customer: replied 2 years ago.
I hear that most Hitachi plasma's have power supply issues. So I wanted to verify it was functioning correctly. I just don't have the information on how to check the power supply as far as turning it to the full on condition. I do have in front of me (my) pin reading from the power supply showing which pin has voltage and which one dose not. as the TV is now
Customer: replied 2 years ago.
Yes Anthony, the screen is going black. Nothing is warm because Nothing is On. Only the Standby.
Expert:  Anthony_Infotech replied 2 years ago.
You should be reading the Va and Vs scan voltages they should be up if the blue light is lit?they are the most important voltages and are marked on a sticky label on the panel
Its my belief they are up now what you need to do is run the set for 15 mins then switch off and feel the heatsinks on the scan boards left and right if they are running they should be warm
Customer: replied 2 years ago.
Ok, I have had the back off the TV for a while now, I have left the TV on while checking systems in general. It clearly has no power to nor am I able to get a reading from the Hot or high side of the power supply. Hence the reason for the above comments. I'm getting power to the power supply, I'm getting standby power to the main board. But I am NOT getting power to anything else. Verified by my volt meter and it is cold to the touch. Plenty of audio no problem. No picture the color is Black it looks like as if the TV were off it looks black but I know it is on because the blue lite is lit and I can hear noise coming out of the speakers.
Customer: replied 2 years ago.
What I'm actually looking for is somebody who can tell me either where I can get the power supply schmatics or tell me which pin to short to physically turn on the high side of the power supply?
Expert:  Anthony_Infotech replied 2 years ago.
OK so its out of standby running blue light lit
Have a look on the board (power)for V and Va or VSUS and Va please let me know if you have those voltages if you do not then disconnect the left and right scan boards from the power and take the voltages again with them disconnected let me know what you get
So are you looking for component level repair??
Customer: replied 2 years ago.
On Hitachi power supplies they don't indicate pins as such. The only thing I have to go by is location of connectors and where they go. I get the fact that it is out of standby, and presumed (on). This is my thinking, tell me if I'm wrong. TV is on, self check passed, audio works, that leads me to the high power pins that run the X & Y sus boards. No reading what so ever.
I know that this could be a very expensive venture, and I am out in the country with no tech around. I figure if I can verify that the power supply is fine, then I stop. If not, then it's worth looking into.
I can't pass this point without verifying that the power supply has the ability to power up.
Customer: replied 2 years ago.
Hello you there?
Expert:  Anthony_Infotech replied 2 years ago.
You are still not answering my question I asked earlier?on the power-board will be two test points or indicators as to where to measure the Vs and Va voltages now are you getting any voltage on these test points?I just need to know that please before we move on.If you dont see these marked test points let me know
Please dont be jumping to your own conclusions I work with this stuff every day if you just follow what I am asking and saying we can move forwards
Customer: replied 2 years ago.
This system of solving problems is Nuts! We were in a conversation about a repair back and forth. Then nothing for a half hour? It would be nice if you would say I'll get back to you, I'm going to lunch jor hold on, or something! So I jumped to the conclusion that you went off line ( which you did!)and assumed that you were done! What other choice do I have?
And if it is normal that I ask a question and then you want me to wait for up to 24 hours for an answer constantly checking my E-mail, Thats unrealistic to say the least!
I told you that I don't have any pin indicator marks (on the PSU) other than PIN numbers. I told you that I do have pin voltages that I have taken myself ( in hopes of identifying them) and that I can identify as to which board they go to. All this is clearly spelled out above. What's more is, Yes I'm looking for a professional at the component level who can identify which pins are which on the power supply so maybe I could tell you what the voltage is at VA and VS. are you with me man?