Is this 55" Hitachi a good buy? (lines on screen)

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I found two bad mosfets on each bad ysus board I have. Location q290 and q291. Marked SGP403 manufactured by SK in a TO263 package. Now just waiting 3-4 weeks for parts to arrive.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

You will need a new buffer too?

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

TV is fixed. It was the ysus board. So if you have one of these TVs that has every other row lit, or it has no display at all yet still has sound, check your ysus, and make sure to put back EVERY screw. I think I broke one of my ysus from only putting in part of the screws.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Wow, I am glad you fixed it.

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Me too, thanks for all the help. I didn't realize the importance of putting back all the screws on these ysus boards. I could have fixed this thing a long time ago with the new ysus I ordered. Unfortunately I assumed that putting 2 of the 8 ground screws in was ok for testing. It was not ok, and kept blowing those two fets on the board.

[tieny]

Re: Is this 55" Hitachi a good buy? (lines on screen)

So not putting all the screws can short fets on ysus boards? O.o Is this true for all panels? If that's the case I'll probably start doing the same. Maybe thats why theres so many cases of Ysus blowing =P

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I have never heard of it with other boards.
However, I have heard of extra buzzing from sustain boards when all screws are not installed...

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

I did in fact get loud buzzing, and a few seconds later the fets blew. I tried a second time with all the screws in, and the TV has been working for a day now. It may have been coincidence.

[tom66]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Will you keep it or sell it?
If you don't mind how much do you have invested in it?

[mattpd]

Re: Is this 55" Hitachi a good buy? (lines on screen)

If I do sell it, I will part it out because it will be worth twice as much. I have way to much invested, maybe $400. I should easily be able to recoup all of it though, and maybe turn a profit. The ysus board that I ended up using was one I bought broken for $35 on ebay when normal price is $100 or more. I fixed it for $4 in parts, and I fixed one of the buffer ICs for $10. So in total, if I wouldn't have wasted money on extra boards, I would have fixed it for $14.

Now I have a logic board I bought from ShopJimmy but never opened, an extra power board that is working, and two broken ysus boards that should be fixable. All of these boards are high priced and in demand on ebay so I shouldn't have a problem selling them.

I may keep the TV, and offer a mail in repair service for this TV on ebay. I have extra parts to fix the buffer boards and ysus boards, and the TV to test my work before mailing back. These buffer boards are $150 a piece and ysus are $100, so I bet people would be willing to pay $100-$150 to repair/check all 3.

[Dennis H]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Wow, This is great thread, glad I found it! I too have a 55HDT52 Hitachi, actually paid that crazy money and bought it new back in late 2005. It had been fine until the picture went black. Mine was the whole screen, could not see anything anywhere, but sound was/is perfect and it would change channels and controls worked etc, just couldn't see any display.
Like Matt I do want to fix it and I finally did get around to pulling the 140lb monster off the wall for a looksie. It had been on the same wall since we bought it and it was pretty dusty, in fact i was a little embarrassed to realized I had not taken the time to clean it periodically. Especially after reading Tom's comments about the Hitachi's really needing a second cooling fan for the big boards. My not cleaning it may have contributed to it's failure, but who knows.

Anyway, once I pulled the back cover off and cleaned the dust off, I started checking the voltage numbers based on diagram I pulled elsewhere off the net.
All the outputs out of the man power board seem to be right on except the CN64 which has the Vs and Va. For those I get no voltage output when I use the gound pins in that plug (5/6) and any of the Vs or Va hots, pins 1/2 and 8/9/10. I expect that i should have gotten the 64 and 83 volts checking that way as that method provided the correct outputs for all the other outputs, CN63, CN68 etc.

Now, funny thing is, if I touch the black lead to the upper far left heat sink, I get 56volts on any pin, 1/2/3/4/8/9/10.

At first I thought that some components may have been bad there, but once I started thinking about it, it looks like all the out put ground paths are connected, so I am guessing the 56 volts I got from grounding at the heat sink instead of the output plug ground pin was due to an open in the hot side somewhere as opposed to the ground side. Then again if I think about it to much, I might prefer to go have a pint or two!

I am sorry for so much talk, but I want to ask if it makes sense to start my looking on that main power board? I don't see any burned IC's or mosfets and the CAP's look ok, although I am not sure I trust them. All but two look normal and the two may be normal, or not...They look flat across the top. These are the two big ones at the top left, 450 volt/390Mf. With the board out of the tv (caps in place on board) I probed them , and the rest i saw in the trail over to the Va and Vs output and they seemed to charge up and then go down to infinity fairly quickly. Now, I know all I did was get a "relative" looksie that may be worthless, but they seemed to behave ok?? There was a smaller cap over by the output plug that did not go to infinity. It stablized at maybe 200 ohms or something. It is C1527 and it looks like it's legs bridge the ground going into the output plug and the hot of the Vs (and I could be very mistaken on that too lol).

I have the board out and can post pics if that will help or can also start a new thread to, either way is fine.

I'd like to trouble shoot this and get it fixed as I prefer to fix things instead of just throw them out.
Thanks for any help
Dennis H.

[ajshoe]

Re: Is this 55" Hitachi a good buy? (lines on screen)

have a 55 Hds52 hitachi. power supply wont bring up CNPPS voltages (5V, 10.5V, 24v) - have checked both standby voltages and they are good. 2 fuses good, no PS schematics available for these. anybody worked on one of these PS ??? could use some help.

[bryoneylar@gmail.com]

Re: Is this 55" Hitachi a good buy? (lines on screen)

Needing help with same tv if you are not busy. Did u fix yours?