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

[tom66]

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

Vs comes from the power supply, unless it is routed through there first. Test it with the Y-sus disconnected.

[mattpd]

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

If I test vs on ysus board I get 3.8v. This voltage comes from the xsus board. Is it malfunctioning?

[tom66]

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

Yeah, sometimes Vs or Vsa.

[mattpd]

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

Could vsus be labeled something else? vs?

[tom66]

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

If you plug it in, do you still get good Vsus, or does it collapse below 1V?

[mattpd]

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

I'm searching hard for a fuse, it's small if its here. There is no short between ground and vcc, va, or vs.

[tom66]

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

Is there a fuse on the board?

[mattpd]

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

I checked every 3 pin component that was labeled "G S D" between S and D and I found no shorts. Could it short between other pins or is there another component that is likely to POP?

[tom66]

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

That should be fine, you will likely find a block are shorted (sharing a heatsink for example), and then you need to remove them one by one until the short goes. Sometimes more than one goes short.

[mattpd]

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

Can I check them in circuit?

[tom66]

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

It might be an interlaced driver, and maybe the bad buffer damaged it somehow. You have a large number of FETs and IGBTs on the board; check them individually for short circuits across source and drain. Also, check local Craigslist for a TV like this which is the victim of a flying Wii controller, or being dropped -- great for getting parts.

[mattpd]

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

Sigh... I got the buffer today in the mail and got it installed no problem. Although it did not fix the odd/even lines it did fix that thick line that existed 3/4 down the screen. I was happy that at least it was not a waste of money, but then BANG! Something blew up (on y-sus board I think) and the picture went out completely.

My theory is that the y-sus was half way dead to begin with (only displaying even lines) and for some reason the other half just blew. This y-sus board looks like it has two indentical circuits, each going to a separate buffer board. I was planning on comparing these two circuits to find the bad component, but now that it is completely blown, I'm SOL. This board is expensive so I would love to fix it. Where would you look first? Going over it with a flashlight now to find what went bang.

[tom66]

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

Think about it another way. Thanks to Hitachi's cost cutting, you got a $3,000 TV (which would cost at least $500 now) for $80 plus parts.

At the time of this TV, Hitachi Media Enterainment was on its last legs. They were hemorrhaging money in the plasma business. So they were cutting costs wherever they could to compete with Samsung and LG who would make TVs last 2-4 years and somehow customers would still come back for more.

[mattpd]

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

15 heat sinks and thermal plaster for less than $5. Thank you ebay. Just think of how cheap hitachi could get them. Weird they didn't include them in a $3,000 TV.

[tom66]

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

Thermal adhesive. (Adhesive which is a good thermal conductor.)

[mattpd]

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

What would I use to attach the heat sinks? The epoxy would make it hard to get good contact with the chip.

[tom66]

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

Oh, I forgot to mention the 550W NEC had two fans. One for the combined Y-sus/Z-sus (all in one board with massive hybrid module), and one for the PSU.

So I think Hitachi were just cutting costs by not including a fan, and it might have lead to buffer failure. You can also install heatsinks on the buffer ICs, Panasonic does this a lot.

[mattpd]

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

Great, thank you.

[tom66]

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

I had the same issue with a Panasonic plasma. Something didn't sync up right when the bottom was out, and I only got an interlaced picture on the top half.

[mattpd]

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

I just ran the tv with the bottom buffer board out and the bottom half of the TV was black as expected but the top half still had the even odd problem. Is this to be expected or do I have more problems?